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Rashid, Ghulam Mustafa, Mirza Habib Ali, Abida Butt, and Abdul Qadir. "A cross-sectional study on knowledge, attitude and practices related to owls in central Punjab, Pakistan." Ornis Hungarica 29, no. 1 (June 1, 2021): 66–81. http://dx.doi.org/10.2478/orhu-2021-0005.
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Abstract Owls are considered as dominant predators for control of rats and mice population in agricultural fields and presently their populations are continuously declining in Punjab, Pakistan. The present study was aimed to assess the knowledge and attitude of people of rural and urban areas about the declining trend of owls. During this survey, more than 1600 people were asked to collect information regarding the owl populations from six localities including Faisalabad, Sialkot, Jhang, Lahore and Bahawalnagar. Four parameters were the major part of the questionnaire: familiarity, misconceptions, awareness about owls and their acceptance as a biological controlling agent. The results revealed that about 95% of people were familiar with owls in the agro-ecosystem. Only 15.6% of people thought that owls should be eliminated; 23.0% were of the opinion that owl’s presence in a locality leads to ruination; 33.3% agreed that the owls presence was a sign of bad omen; 41.8% considered them as signs of foolishness; 47.0% believed that owl’s body parts were used for black magic purposes. In contrast, 50% of people acknowledged that owls are beneficial to humans; 60.3% knew that owls are the enemies of rodents, 67.7% agreed that they are suppressors of rats and mice and 63.8% agreed that artificial nest boxes can serve as their nests and roosts. It was encouraging to know that 74.8% showed their willingness to enhance the owl’s population on their farms, and 74.0% were willing to permit the installation of nest boxes in or near the villages. The study of attitudes of respondents towards owl will help to develop an effective conservation strategy and to boost owl’s population in croplands for biological control of rats and mice.
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Crozier, Michelle L., Mark E. Seamans, R. J. GutiÉRrez, Peter J. Loschl, Robert B. Horn, Stan G. Sovern, and Eric D. Forsman. "Does The Presence of Barred Owls Suppress the Calling Behavior of Spotted Owls?" Condor 108, no. 4 (November 1, 2006): 760–69. http://dx.doi.org/10.1093/condor/108.4.760.
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Abstract Abstract Barred Owls (Strix varia) have expanded their range throughout the ranges of Northern (Strix occidentalis caurina) and California Spotted Owls (S. o. occidentalis). Field observations have suggested that Barred Owls may be behaviorally dominant to Spotted Owls. Therefore, we conducted a test of behavioral dominance by assessing responsiveness of Spotted Owls to conspecific calls when they were in the simulated presence (i.e., imitation of Barred Owl vocalizations) of a Barred Owl. We hypothesized that Spotted Owls would be less likely to respond to conspecific calls in areas where Barred Owls were common. We used a binary 2 × 2 crossover experimental design to examine male Spotted Owl responses at 10 territories randomly selected within two study areas that differed in abundance of Barred Owls. We also conducted a quasi experiment at four study areas using response data from any Spotted Owl (male or female) detected following exposure to Barred Owl calls. We inferred from the crossover experiment that the simulated presence of a Barred Owl might negatively affect Spotted Owl responsiveness. Both subspecies of Spotted Owl responded less to Spotted Owl calls after exposure to Barred Owl calls, Northern Spotted Owls responded less frequently in areas having higher numbers of Barred Owls, and California Spotted Owls responded less frequently than Northern Spotted Owls overall.
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Martinez, David R. "FOOD HABITS AND TROPHIC ATTRIBUTES OF THE MAGELLANIC HORNED OWL (BUBO MAGELLANICUS) IN PATAGONIAN STEPPE, SOUTHERNMOST CHILE." Ornitología Neotropical 31, no. 1 (June 30, 2020): 47–51. http://dx.doi.org/10.58843/ornneo.v31i1.471.
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For most of southern South America, the food habits of Magellanic Horned owls (Bubo magellanicus) are well known. In Chile, several researchers have reported the owl’s diet in northern xerophytic environments, as well as subpolar forests; however, other than a short note on the owls’ summer diet in Punta Dungeness, no major studies have documented the food habits of Magellanic Horned owls in the Chilean Patagonian steppe. Based on 278 fresh pellets, we reported the food habits of owls inhabiting two sites located at > 52°S in the southernmost Patagonian steppe in continental Chile, and compared our findings with those reported for owls inhabiting eight localities from 39 to 52°S in the Argentinean Patagonian steppe. Our results indicate that in Patagonian steppe environments of both Argentina and Chile, the Magellanic Horned Owl is a generalist predator, which consumes whatever prey available, ranging in size from inver- tebrates to introduced juvenile lagomorphs. Because all five major vertebrate prey here reported (Abrothrix olivacea, Loxodontomys micropus, Microcavia australis, Reithrodon auritus, Lepus europaeus) are broadly distributed in the Argentinean Patagonian steppe and occur abundantly from 36°S southwards to the Strait of Magellan and Isla Grande de Tierra del Fuego, their generalized occurrence as prey does not allow for expression of latitudinal trends in species composition in the owl’s diet.
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OGADA, DARCY L., and PAUL MURIITHI KIBUTHU. "Conserving Mackinder's eagle owls in farmlands of Kenya: assessing the influence of pesticide use, tourism and local knowledge of owl habits in protecting a culturally loathed species." Environmental Conservation 35, no. 3 (September 2008): 252–60. http://dx.doi.org/10.1017/s0376892908005006.
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SUMMARYFarmlands can be good habitat for owls and owls can benefit farmers, but pesticide use can negatively affect owls and within many regions of Africa owls are loathed owing to beliefs that they bring misfortune or death. Since 1997, a small-scale owl tourism initiative that educates farmers about owls and benefits them financially has been operating in central Kenya. Pesticide use, farmers' beliefs and knowledge about owls, and the impacts that tourism can have on farmers' attitudes and behaviour towards owls in rural Kenya were surveyed. Agricultural pests were the most serious problem facing farmers, though only 28 % of farmers said they controlled vertebrate pests using pesticides. The insecticide carbofuran was often misused to kill vertebrate pests. Common control measures were either to ‘do nothing’ or to chase pests from farms. Farmers knew of Mackinder's eagle owls living adjacent to their farms, but 68 % said they didn't adhere to the culturally negative beliefs about owls. Knowledge of owl diet amongst farmers was high (75 %). Farmers who benefited from owl tourism were more likely to know more about owl diet and habits. Where farmers gained financial benefits from tourism or knew more about owls, they were more likely to categorize owls as ‘good’, but farmers who knew about owl diet were more likely to use pesticides or kill owl prey on their farms. Though knowledge of owls did not have a positive effect on farmers' behaviour toward owls, this was probably the result of a lack of ecological literacy rather than any deliberate antagonism toward owls. Financial rewards are very important to poor farmers, but may not result in actions that enhance species conservation unless farmers have a basic understanding of ecological processes.
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Kelly, Elizabeth G., Eric D. Forsman, and Robert G. Anthony. "Are Barred Owls Displacing Spotted Owls?" Condor 105, no. 1 (February 1, 2003): 45–53. http://dx.doi.org/10.1093/condor/105.1.45.
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Abstract Barred Owls (Strix varia) have expanded their range into the Pacific Northwest, and anecdotal evidence suggests that they may be displacing the federally threatened Northern Spotted Owl (Strix occidentalis caurina). Our objectives were to describe the current status of Barred Owls in Oregon and compare occupancy of Spotted Owls in historic Spotted Owl territories before and after Barred Owls were first detected in those territories. Between 1974 and 1998, we estimated that 706 different Barred Owl territories were located in Oregon. From 1989–1998 an average of 60 new Barred Owl territories were located in Oregon each year. In Spotted Owl demographic study areas in Oregon and Washington, Barred Owl detections increased at Spotted Owl territories from 1987–1999. Occupancy of Spotted Owl territories declined after Barred Owls were detected within 0.80 km of the territory center. When Barred Owls were detected 0.81–2.40 km from Spotted Owl territory centers, occupancy of Spotted Owls was only marginally less than at territories without Barred Owls. This suggests that the frequency and intensity of interactions between the two species is negatively associated with distance between them. Our results suggest that land managers and regulatory agencies should regard Barred Owls as a threat to Spotted Owls, particularly if Barred Owls continue to increase in number as they have during the past 25 years. ¿Está Strix varia Desplazando a Strix occidentalis caurina? Resumen. Desde su expansión hacia el Pacífico Noroeste, existe evidencia anecdótica de que Strix varia podría estar desplazando a S. occidentalis caurina. Nuestros objetivos fueron describir el estatus actual de S. varia en Oregon y comparar la ocurrencia de S. occidentalis caurina en sus territorios históricos antes y después de que S. varia se detectó por primera vez en dichos territorios. Entre 1974 y 1998, estimamos que se confirmaron 706 territorios diferentes de S. varia en Oregon. Entre 1989 y 1998, se localizaron en promedio 60 nuevos territorios de S. varia anualmente. En áreas con estudios demográficos de S. occidentalis caurina en Oregon y Washington, las detecciones de S. varia en territorios de S. occidentalis caurina se incrementaron entre 1987 y 1999. En comparación con territorios sin S. varia, la ocupación de territorios de S. occidentalis caurina disminuyó luego de que se detectaron individuos de S. varia a menos de 0.80 km del centro del territorio. Cuando se detectaron individuos de S. varia entre 0.81 y 2.40 km del centro de los territorios, la ocupación de éstos fue sólo marginalmente menor que en territorios sin S. varia. Esto sugiere que la frecuencia e intensidad de la interacción entre las dos especies está asociada con la distancia entre ellas. Nuestros resultados sugieren que las autoridades ambientales y de regulación deben considerar a S. varia como una amenaza para S. occidentalis caurina, particularmente si los números de S. varia se siguen incrementando como en los últimos 25 años.
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Hussain, Mubasher, and Jamil Akhtar. "Owls in Islam and Pakistan: Loopholes and Suggestions for Conservation and Management of this Highly Ecologically Important Niche." Journal of Bioresource Management 8, no. 1 (January 27, 2021): 40–45. http://dx.doi.org/10.35691/jbm.1202.0164.
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Due to their vital ecological significance, owls drew the attention of several groups working on wildlife protection and conservation management across the globe. Hence, certain legal provisions have been articulated in the wildlife protection acts of the advanced countries to ensure full legal protection of wildlife including owls. Although there are certain laws concerning the protection of wild life in Pakistan, the specific and consistent legal provisions are still required for owl’s full protection. This article highlights a dire need of the articulation of such provisions respecting the prohibition of owl hunting on several religious, legal and ecological grounds.
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Grossman, S. R., S. J. Hannon, and A. Sánchez-Azofeifa. "Responses of Great Horned Owls (Bubo virginianus), Barred Owls (Strix varia), and Northern Saw-whet Owls (Aegolius acadicus) to forest cover and configuration in an agricultural landscape in Alberta, Canada." Canadian Journal of Zoology 86, no. 10 (October 2008): 1165–72. http://dx.doi.org/10.1139/z08-095.
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Studies on the effects of forest fragmentation on birds have focussed primarily on passerines, with few studies on owls. We assessed the influence of forest amount and configuration on the abundance and distribution of three species of forest owls, Great Horned Owl ( Bubo virginianus (Gmelin, 1788)), Barred Owl ( Strix varia Barton, 1799), and Northern Saw-whet Owl ( Aegolius acadicus (Gmelin, 1788)), in agricultural landscapes with varying amounts of forest cover in central Alberta, Canada. All three species were positively associated with forest cover: Barred Owls were most prevalent in landscapes with >66% forest cover, Great Horned Owls in landscapes with between 36% and 65% forest cover, and Northern Saw-whet Owls in landscapes with between 16% and 100% forest cover. Regression models containing configuration variables were chosen as best models using AIC for all three species. Great Horned Owls were most abundant in landscapes with high heterogeneity: more forest–nonforest edges and higher forest patch area variation. Barred Owls were more likely to occur in landscapes with larger forest patch areas and Northern Saw-whet Owls were more abundant in landscapes that were more connected. These relationships are consistent with predictions based on body size of owls and local habitat relationships described in the literature.
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Hamer, Thomas E., Eric D. Forsman, and Elizabeth M. Glenn. "Home Range Attributes and Habitat Selection of Barred Owls and Spotted Owls in an Area of Sympatry." Condor 109, no. 4 (November 1, 2007): 750–68. http://dx.doi.org/10.1093/condor/109.4.750.
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Abstract We compared home range areas and habitat selection of radio-marked Spotted Owls (Strix occidentalis) and Barred Owls (Strix varia) in an area of sympatry in the northern Cascade Range of Washington in 1986–1989. On average, home ranges of Spotted Owls were 3–4 times larger than ranges of Barred Owls, and there was little overlap of home ranges during the breeding season. Ranges of both species tended to expand during winter. Home range size of both species was negatively correlated with the amount of old forest, but the negative slope of the regression was much steeper for Spotted Owls than for Barred Owls. For both species, home ranges of individual owls typically had high overlap among seasons and years, indicating high site fidelity. Barred Owls generally occupied home ranges at lower elevations than Spotted Owls (mean = 386 ± 27 m vs. 750 ± 68 m). Both species tended to use old forests more than expected, but Spotted Owls tended to use other cover types less than expected, whereas Barred Owls used most other cover types in proportion to their availability. We suggest that Spotted Owls may use larger ranges than Barred Owls because they prey selectively on a few species of nocturnal mammals, whereas Barred Owls forage more evenly across a broad range of prey types, including diurnal and aquatic species. The low overlap of Barred Owl and Spotted Owl home ranges suggests that territorial Barred Owls exclude Spotted Owls from their territories, at least during the breeding season, thus reducing the amount of habitat available to Spotted Owls.
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Cooke, Raylene, Rohan Bilney, and John White. "Potential competition between two top-order predators following a dramatic contraction in the diversity of their prey base." Animal Biology 61, no. 1 (2011): 29–47. http://dx.doi.org/10.1163/157075511x554400.
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AbstractTwo sympatric native top-order predators, the sooty owl (Tyto tenebricosa tenebricosa) and powerful owl (Ninox strenua) coexist throughout much of their range in south-eastern Australia. Following European settlement, however, major changes in resource availability for these predators potentially resulted in increased competition, especially for food. This study examined ecological attributes of both species, including intersexual differences in the sooty owl, potential resource partitioning and whether competition may be occurring. Dietary overlap was high between female sooty owls and powerful owls (0.90), compared to overlap between male sooty owls and powerful owls (0.67), with three mammalian species contributing over 74% of their diets. Sooty and powerful owls coexisted throughout the study region, regularly roosting within the same vegetation types, and in similar locations, although microhabitat differences were apparent. Sooty owls displayed aseasonal breeding, although a peak in fledging in spring coincided with powerful owl breeding. Both species exclusively nested in similar size mountain grey gums (Eucalyptus cypellocarpa), however, hollow characteristics differed slightly. Significant divergence along a single niche dimension was not detected between powerful and sooty owls, as they had similar diets, habitat usage and activity times, potentially resulting in competition. Reproductive output was low for both species, however, the degree to which competitive interactions influenced this remains unknown. To minimise potential competition, longterm feral predator control and improved habitat management is recommended to increase the density and diversity of small terrestrial mammals, as this should result in diversification of the sooty owl diet, reducing dietary overlap with powerful owls.
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Charter, Motti, Ido Izhaki, Kobi Meyrom, Shauli Aviel, Yossi Leshem, and Alexandre Roulin. "The Relationship between Weather and Reproduction of the Barn Owl Tyto Alba in a Semi-Arid Agricultural Landscape in Israel." Avian Biology Research 10, no. 4 (November 2017): 253–58. http://dx.doi.org/10.3184/175815617x15063340995365.
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Even though the Barn Owl ( Tyto alba) is distributed worldwide, little information is available on how weather affects Barn Owl breeding outside of Europe and North America. For instance, if cold temperatures can negatively influence population dynamics in temperate regions, heat could have a similar negative effect in arid regions. We have studied a breeding population of Barn Owls in a semi-arid agricultural environment over 13 years in Israel in order to determine whether lack of rain and hot ambient temperatures impair Barn Owl reproductive success. The percentage of nest boxes occupied by Barn Owls was not related to any of the weather variables, whereas the number of nestlings per Barn Owl pair and the percentage of pairs that succeeded to fledge young was lower in years when it started to rain later in the season and when the minimum daily temperature was higher during the breeding season. In comparison to temperate regions, heat is detrimental to Barn Owl breeding and early precipitation is probably important in boosting vegetation and, in turn, the abundance of small mammals, the Barn Owl's staple food.
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Urita, C., S. Kusuda, and N. Rooney. "Physiological and behavioural assessments of stress levels in owls housed at owl cafes." Animal Welfare 31, no. 3 (August 31, 2022): 283–92. http://dx.doi.org/10.7120/09627286.31.3.001.
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Owl cafes, where customers view and interact with owls, have become popular in Japan. There are multiple aspects of the environment which may be stressful to nocturnal owls, including lighting, tethering and frequent interactions with humans but, to date, welfare has not been investigated. This preliminary study examines the effects of owl cafes and customers on the physiological stress (faecal corticosterone levels [FCL]) and behaviour of the owls. Seven eagle owls (Bubo bubo ) and two African scops owls (Ptilopsis leucotis), in two cafes, were studied over an eight-day period. Cafe A (n = 5) was closed for one day per week, whilst cafe B (n = 4) was open every day. In cafe A there was higher FCL in owls during open days than closed days suggesting that the conditions on open days increase stress in owls. Eight of nine owls showed evidence of some aversion or avoidance of humans, whilst no affiliative behaviours were observed. The number of visitor interactions was not associated with the level of physiological stress; and when comparing owls, there was a tendency for individual owls with a higher percentage of aversive responses to customers to also have higher FCL. Close human interactions of a negative nature, that result in aversion, may be a significant stressor, but further research is required.
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Berry, Glori. "Season and Age as Factors in Barred Owl (Strix varia) Admissions." Wildlife Rehabilitation Bulletin 30, no. 1 (June 30, 2012): 15–22. http://dx.doi.org/10.53607/wrb.v30.58.
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Barred owl admittance data from Avian Haven, a wildlife rehabilitation facility in central Maine, were examined from April 2005 through March 2011. During this time, 231 barred owls were admitted to the facility, excluding nestlings. A significantly greater number of owls were admitted in the fall and winter months than in the spring and summer months; yearly variations in the fall and winter month admissions also were significant, while those for the spring and summer month admissions were not. Furthermore, a statistically significant proportion of 44 barred owls aged during the 2010/2011 fall/winter season were hatch–year birds, suggesting that yearly variations in barred owl admittance numbers are directly correlated with the number of dispersing hatch–year birds. Finally, in aging the barred owls for this study, a technique using an ultraviolet light source in the form of a black light to examine the fluorescence of porphyrin pigments in the feathers of owls was investigated. It was found to be reliable in differentiating hatch–year owls from adult (after–hatch–year) owls having undergone a partial molt, and has the potential for becoming the definitive method for aging barred owls in a rehabilitation setting.
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Nemček, Vladimír, and Barbara Kohl. "Owls’ responses to forest conservation in the Alps." Raptor Journal 17, no. 1 (June 1, 2023): 49–56. http://dx.doi.org/10.2478/srj-2023-0006.
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Abstract As inhabitants of cavities, some owl species benefit from natural processes, different tree compositions and higher volumes of dead wood. We assumed that protected areas would have a positive impact on the owl community. We compared the abundance of calling owls on 22 lines in managed versus protected forests. Here, we recorded the acoustic communication of owls. The composition of the owl community did not differ between areas. However, we found the impact of forest landscape integrity index and altitude on the diversity of owls. Forests in protected areas probably need time to develop natural and heterogeneous habitat structures. The conservation priority should be to increase the integrity of the forests. Our results also confirmed that managed forests can have a high diversity of owls.
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Slaght, Jonathan C., Sergei G. Surmach, and R. J. Gutiérrez. "Riparian old-growth forests provide critical nesting and foraging habitat for Blakiston's fish owl Bubo blakistoni in Russia." Oryx 47, no. 4 (August 6, 2013): 553–60. http://dx.doi.org/10.1017/s0030605312000956.
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AbstractConservation efforts for Blakiston's fish owl Bubo blakistoni in Russia are limited, partly because habitat use by these rare owls is poorly known. We therefore studied nesting and foraging habitat characteristics of Blakiston's fish owls in Primorye, Russia. We sampled habitat at 14 nest sites, 12 nest stand sites and 13 random sites; we also sampled rivers within 14 fish owl home ranges across our 20,213 km2 study area. We found that large old trees and riparian old-growth forest were the primary characteristics of nest and foraging sites, respectively. Large trees were probably used as nest sites because they have cavities large enough to accommodate these birds. Big trees are also important because they are primary sources of large woody debris in rivers, which enhances suitable habitat for salmon, the owl's primary prey. Based on habitat characteristics, nest sites were correctly distinguished from random sites 74% (Kappa = 0.48) of the time, nest stands from random sites 56% (Kappa = 0.12) of the time, and used sites from available foraging sites 68% (Kappa = 0.36) of the time. The management and conservation of old-growth forests is essential for sustaining this species because they are central to the owls' nesting and foraging behaviour. Moreover, conservation of these forests sustains habitat for many other species.
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Richards, Ngaiou L., Pierre Mineau, David M. Bird, Pierre Wery, Jacques Larivée, and Jason Duffe. "First Observations of an Eastern Screech-Owl, Megascops asio, Population in an Apple-Producing Region of Southern Quebec." Canadian Field-Naturalist 120, no. 3 (July 1, 2006): 289. http://dx.doi.org/10.22621/cfn.v120i3.318.
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Baseline information was collected on a local Eastern Screech-Owl population found in the apple-producing region of Saint-Hilaire and Rougemont, Quebec, as part of a larger study on pesticide exposure conducted between 2000 and 2003. Screech-Owls visited or occupied 41 of 89 nest boxes installed in 12 orchards and 2 control locations. The mean height of occupied nest boxes was 3.83 m (2.00 – 5.80 m). Squirrels, Sciurus and Tamiasciurius sp., and chipmunks, Tamias striatus, Northern Flickers, Colaptes auratus, and wasps were the owls’ primary competitors for the boxes. Intact Screech-Owl pellets retrieved from nest boxes (n = 82) had a mean length and width of 3.57 and 1.44 cm, respectively, and weighed a mean of 1.77 g. Screech-Owls in the study area consumed a variety of small mammal, avian, insect and aquatic prey. Of these, Meadow Voles, Microtus pennsylvanicus, were the predominant prey item identified in pellets, and Mourning Doves, Zenaida macroura, were the primary avian prey found in nest boxes. In Canada, the owl’s trend status remains largely unknown. The species is currently listed as “Not at Risk”, based on an assessment conducted for COSEWIC in 1986. Given that a limited amount of information exists on the natural history and ecology of the species in Quebec, we also generated a map of the owl’s distribution in the province, using data from ornithological databases and rehabilitation facilities. Potential risks to the species within the province, particularly pesticide exposure and habitat loss, are briefly addressed and follow-up studies are discussed.
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Žlabravec, Zoran, Al Vrezec, Brigita Slavec, Urška Kuhar, Olga Zorman Rojs, and Joško Račnik. "Herpesvirus Infection in a Breeding Population of Two Coexisting Strix Owls." Animals 11, no. 9 (August 27, 2021): 2519. http://dx.doi.org/10.3390/ani11092519.
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Birds are a frequent host of a large variety of herpesviruses, and infections in them may go unnoticed or may result in fatal disease. In wild breeding populations of owls, there is very limited information about the presence, impact, and potential transmission of herpesvirus. The herpesvirus partial DNA polymerase gene was detected using polymerase chain reaction in oropharyngeal swabs of 16 out of 170 owls examined that were captured in or near nest boxes. Herpesvirus was detected in Ural owls (Strix uralensis), in both adults and young, but not in tawny owls (Strix aluco). In yellow-necked mice (Apodemus flavicollis), as the main prey of tawny owls and Ural owls in the area, herpesvirus was detected in the organs of 2 out of 40 mice captured at the same locations as the owls. Phylogenetic analysis showed that the herpesvirus sequences detected in the Ural owls differed from the herpesvirus sequences detected in the yellow-necked mice. The results indicate that herpesvirus infection exists in the breeding wild Ural owl population. However, herpesvirus-infected owls did not show any clinical or productivity deviances and, based on a phylogenetic comparison of detected herpesvirus sequences and sequences obtained from Genbank database, it seems that mice and other rodents are not the source of owl infections. The most probable transmission pathway is intraspecific, especially from adults to their chicks, but the origin of herpesvirus in owls remains to be investigated.
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Shanmugavel Sureshmarimuthu, Santhanakrishnan Babu, Nagaraj Rajeshkumar, and Honnavalli Nagaraj Kumara. "Get my head around owls: people perception and knowledge about owls of Andaman Islands." Journal of Threatened Taxa 13, no. 12 (October 26, 2021): 19725–32. http://dx.doi.org/10.11609/jott.7594.13.12.19725-19732.
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Understanding people’s perceptions and knowledge about birds in an endemic bird area is a prerequisite for bird conservation. This is more so in the case of non-charismatic birds such as owls. In this context, we conducted a questionnaire survey about owls in the North Andaman Island between January 2016 and 2018. We interviewed 203 respondents from six market places in North Andaman tehsil, and collected data on their socio-economic status as well as their knowledge on owls. Although all the respondents were familiar with owls, only 9% of them identified all species of owls in the Andaman Islands. Around 98% of respondents were aware of owl diets, either partly or wholly. We found several superstitious beliefs revolving around owls. Two species, Otus sunia and Ninox obscura were associated with negative beliefs while Tyto deroepstorffi was associated with positive beliefs. Generalized linear model with the demographical predictors showed that positive attitudes towards owls is associated with age (older), education (literacy), revenue villages and temporary houses. We conclude that Tyto deroepstorffi had the highest positive values among islanders and hence, may be considered as a focal species to create awareness about owls and to protect other endemic owls of the Andaman Islands. Awareness programmes targeting younger, illiterate people, and land encroachers may help in conservation of cryptic owl species of Andaman.
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Bilney, Rohan J., Raylene Cooke, and John White. "Change in the diet of sooty owls (Tyto tenebricosa) since European settlement: from terrestrial to arboreal prey and increased overlap with powerful owls." Wildlife Research 33, no. 1 (2006): 17. http://dx.doi.org/10.1071/wr04128.
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The current diet of the sooty owl (Tyto tenebricosa) was determined by analysing freshly regurgitated pellets collected beneath their roosting sites in East Gippsland, Victoria. Comparisons were then made with: (i) prehistoric and historic diet from bone deposits found in cave roosts, and (ii) diet of a sympatric owl species, the powerful owl (Ninox strenua). Sooty owls consumed a large array of terrestrial mammal species before European settlement, but only three terrestrial species were detected in their current diet, a reduction of at least eight species since European settlement. To compensate, sooty owls have increased their consumption of arboreal prey from 55% to 81% of their diet. Arboreal species are also a major component of the powerful owl diet and this prey shift by sooty owls has increased dietary overlap between these two species. Predation by foxes (Vulpes vulpes) and other feral species is likely to have reduced the amount of terrestrial prey available to sooty owls since European settlement. Investigation of changes in the diet of sooty owls may offer a unique monitoring system for evaluating the ability of fox-control strategies to influence increases in numbers of critical-weight-range mammals.
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Smith, N. Adam, Thomas A. Stidham, and Jonathan S. Mitchell. "The First Fossil Owl (Aves, Strigiformes) From the Paleogene of Africa." Diversity 12, no. 4 (April 23, 2020): 163. http://dx.doi.org/10.3390/d12040163.
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The relatively extensive fossil record of owls (Aves, Strigiformes) in North America and Europe stands in stark contrast to the paucity of fossil strigiformes from Africa. The first occurrence of a fossil owl from the Paleogene of Africa extends the fossil record of this clade on that continent by as much as 25 million years, and confirms the presence of large-sized owls in Oligocene continental faunas. The new fossil is tentatively referred to the Selenornithinae, a clade of large owls previously restricted to Europe. This new fossil owl was likely similar in size to the extant Eagle Owls of the genus Bubo, and suggests that the niche of large, volant, terrestrial avian predator, although relatively rare throughout avian evolutionary history, may be an ecological role that was more common among extinct owls than previously recognized.
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Domahidi, Zoltan, Scott E. Nielsen, Erin M. Bayne, and John R. Spence. "Boreal Owl (Aegolius funereus) and Northern Saw-whet Owl (Aegolius acadicus) breeding records in managed boreal forests." Canadian Field-Naturalist 134, no. 2 (September 21, 2020): 125–31. http://dx.doi.org/10.22621/cfn.v134i2.2146.
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During the 2016 breeding season we monitored 169 nest boxes suitable for Boreal Owl (Aegolius funereus) and Northern Saw-whet Owl (Aegolius acadicus) in high-latitude (>55°N) boreal forests of northwestern Alberta affected by partial logging. Despite the large number of boxes deployed, the number of boxes used by Boreal and Northern Saw-whet Owls was small. Boreal Owls used nest boxes (n = 4) in conifer-dominated stands with three being in uncut blocks and the other in a 50% green tree retention cut-block. In contrast, Northern Saw-whet Owls used boxes (n = 4) in a broader range of cover types, breeding in boxes placed in stands with at least 20% post-harvest tree retention. Although both species successfully bred in the same landscape, Boreal Owls produced fewer eggs (mean = 2.5) and raised fewer young (mean = 0.5) than Northern Saw-whet Owls (5 and 2.25, respectively). Furthermore, our observed Boreal Owl egg production was lower than has been found for the same species nesting in nest boxes in different regions or forest types. In contrast, breeding parameters of Northern Saw-whet Owls were similar to that found in nest boxes in the eastern boreal region of Canada and in the southern part of its range.
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Zhao, Wei, Mingqin Shao, Naifa Liu, and Sen Song. "Diets of little owls and long-eared owls in Northwestern China." Animal Biology 58, no. 2 (2008): 211–19. http://dx.doi.org/10.1163/157075608x328044.
Full textAbstract:
AbstractWe compared diets of little owls (Athene noctua) and long-eared owls (Asio otus) in the Minqin Desert in northwestern China. Based on prey numbers, little owls fed mainly on mammals (51.0%) and beetles (46.9%), whereas long-eared owl fed almost exclusively on mammals (96.4%). Based on biomass, both species fed mainly on mammals. Mus musculus, Cricetulus barabensis and Meriones meridianus were the three most common mammals taken by both species. Seasonal variation was found in the diets of both species. Food niche breadth was 3.4 for little owls vs 2.9 for long-eared owls. Dietary overlap between the two species was 49.6%, but varied from 4.0% in April to 96% in January. Dietary overlap of mammals was 97.9%, indicating that both owls fed on similar rodent assemblages. Mean mass of prey was 25.8 ± 22.7 g for long-eared owls and 15.5 ± 22.7 g for little owls. The mean length of tibias of mammals in pellets also indicted that, on average, long-eared owls (18.1 ± 5.6 mm) took larger prey than little owls (16.2 ± 4.7 mm).
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Gold, Joshua I., and Eric I. Knudsen. "Hearing Impairment Induces Frequency-Specific Adjustments in Auditory Spatial Tuning in the Optic Tectum of Young Owls." Journal of Neurophysiology 82, no. 5 (November 1, 1999): 2197–209. http://dx.doi.org/10.1152/jn.1999.82.5.2197.
Full textAbstract:
Bimodal, auditory-visual neurons in the optic tectum of the barn owl are sharply tuned for sound source location. The auditory receptive fields (RFs) of these neurons are restricted in space primarily as a consequence of their tuning for interaural time differences and interaural level differences across broad ranges of frequencies. In this study, we examined the extent to which frequency-specific features of early auditory experience shape the auditory spatial tuning of these neurons. We manipulated auditory experience by implanting in one ear canal an acoustic filtering device that altered the timing and level of sound reaching the eardrum in a frequency-dependent fashion. We assessed the auditory spatial tuning at individual tectal sites in normal owls and in owls raised with the filtering device. At each site, we measured a family of auditory RFs using broadband sound and narrowband sounds with different center frequencies both with and without the device in place. In normal owls, the narrowband RFs for a given site all included a common region of space that corresponded with the broadband RF and aligned with the site's visual RF. Acute insertion of the filtering device in normal owls shifted the locations of the narrowband RFs away from the visual RF, the magnitude and direction of the shifts depending on the frequency of the stimulus. In contrast, in owls that were raised wearing the device, narrowband and broadband RFs were aligned with visual RFs so long as the device was in the ear but not after it was removed, indicating that auditory spatial tuning had been adaptively altered by experience with the device. The frequency tuning of tectal neurons in device-reared owls was also altered from normal. The results demonstrate that experience during development adaptively modifies the representation of auditory space in the barn owl's optic tectum in a frequency-dependent manner.
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Gomez, Eres A., Heather L. Prestridge, and Jennifer A. Smith. "Anthropogenic threats to owls: Insights from rehabilitation admittance data and rodenticide screening in Texas." PLOS ONE 18, no. 8 (August 4, 2023): e0289228. http://dx.doi.org/10.1371/journal.pone.0289228.
Full textAbstract:
Owls (Strigiformes) provide myriad ecosystem services and are sentinels for ecosystem health. However, they are at continued risk from anthropogenic threats such as vehicle collisions, entanglement with human-made materials, and exposure to anticoagulant rodenticides (ARs), a widespread pesticide known to affect owls. Texas is an important region for numerous migratory and non-migratory owl species in the United States (US), yet assessments of threats owls face here are lacking preventing the development of informed conservation strategies. This study coupled assessment of admittance data from two wildlife rehabilitation centers in Texas with AR liver screening to (1) identify which species of owls are commonly admitted, (2) evaluate seasonality of admittance, and (3) assess causes of admittance for owls in Texas. Between 2010 and 2021, 1,620 owls were admitted into rehabilitation, representing eight species of which the Great-horned Owl (Bubo virginianus) was the most common. For all owls combined admittance rates were highest in the spring, driven by an influx of juveniles (n = 703, 43.40%). The leading cause of admittance amongst species was ‘no apparent injury’ (n = 567, 34.94%). Where clear diagnoses could be made, the leading causes of admittances were ‘entrapment in human infrastructure’ (n = 100, 6.11%) and ‘collision with vehicles’ (n = 74, 4.56%). While the admittance data did not reveal any cases of AR poisoning, liver screening demonstrated high incidences of AR exposure; of 53 owls screened for ARs, 50.94% (n = 27) tested positive with 18 showing exposure to multiple ARs. Brodifacoum was the most frequently detected AR (n = 19, 43.18%) and seven owls (25.93%) tested positive within lethal ranges. Our results suggest that owls in Texas are at risk from myriad anthropogenic threats and face high exposure rates to ARs. In doing so, our results can inform conservation strategies that mitigate anthropogenic threats faced by owls in Texas and beyond.
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Comay, Orr, Efrayim Ezov, Yoram Yom-Tov, and Tamar Dayan. "In Its Southern Edge of Distribution, the Tawny Owl (Strix aluco) Is More Sensitive to Extreme Temperatures Than to Rural Development." Animals 12, no. 5 (March 3, 2022): 641. http://dx.doi.org/10.3390/ani12050641.
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Populations at the warm edge of distribution are more genetically diverse, and at the same time are more susceptible to climate change. Between 1987–1996, we studied Tawny Owls in Israel, the species’ global southern edge of distribution and a country undergoing a rapid land cover transformation for over a century. To assess the potential impacts of land cover transformation, we modelled the species’ most suitable habitat and climate and analyzed how climate and habitat affected the nesting success and prey selection. Moreover, we monitored Tawny Owl juveniles’ survival and ontogeny from eggs to dietary independent young, to find out whether the Israeli population is a sink. While the species distribution model correctly predicted the Tawny Owl’s densest areas of occurrence, it failed to predict its occurrence in adjacent regions. The model also predicted that areas included in the species’ historical range remained suitable habitats. The number of fledglings increased with precipitation and in rural settings but was adversely affected by extreme temperatures. While voles dominated the diet in all habitats, the Tawny Owl’s diet is considerably more variable than other Israeli owls. Our results suggest that the Tawny Owl can adapt to rural-agricultural environments, but is susceptible to climate change.
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JAKOSALEM, P. GODFREY C., NIGEL J. COLLAR, and JENNIFER A. GILL. "Habitat selection and conservation status of the endemic Ninox hawk-owl on Cebu, Philippines." Bird Conservation International 23, no. 3 (July 26, 2012): 360–70. http://dx.doi.org/10.1017/s0959270912000317.
Full textAbstract:
SummaryThe largely deforested island of Cebu, Philippines, hosts a forest-dwelling hawk-owl identified in the literature as Ninox philippensis spilonota but which is in fact a Cebu island endemic species, soon to be named. To determine the current distribution and habitat requirements of this hawk-owl, the five largest of 11 remaining forest patches on Cebu were surveyed between March and June 2011, involving 64 post-sunset 500-m walked transects with playback and habitat assessments. Radio-telemetry studies were also conducted on 10 owls but only for 3–5 days per owl as they removed the transmitters. A total of 52 owls were located across all five forests (at 16 sites two owls responded together to playback) but only the largest forest, Alcoy, contained enough transects for analyses of habitat in relation to owl distribution. Alcoy stands on steep-sided hills and some planting of exotic species occurs within it. Owls were detected in forest interior, forest edge and forest-plantation mix in Alcoy, and on ridges and in gullies despite lower tree densities and greater proximity to clearings in the gullies. However, parts of Alcoy experience strong winds, and owl occupancy decreased significantly with increasing wind speed. Home ranges for the 10 radio-tagged owls were estimated to cover ∼10 ha, although given the short tracking periods this may be an underestimate. Suitable forest studied covers roughly 1,670 ha, with six unstudied forests totalling 250 ha, so assuming a pair every 10 ha would give a tentative global population estimate of ∼ 200 pairs of Cebu Hawk-owls, and even fewer if home ranges are larger than estimated. This, coupled with continuing habitat degradation, triggers the IUCN Red List category ‘Endangered’. Tree cavities suitable for nests may be limiting, and nest-box provision could be explored, provided this does not increase predator pressure on other rare species.
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Hanson, Chad T., Derek E. Lee, and Monica L. Bond. "Disentangling Post-Fire Logging and High-Severity Fire Effects for Spotted Owls." Birds 2, no. 2 (April 14, 2021): 147–57. http://dx.doi.org/10.3390/birds2020011.
Full textAbstract:
The Spotted Owl is a rare and declining raptor inhabiting low/middle-elevation forests of the Pacific Northwest, California, and the Southwest in the USA. It is well established that Spotted Owls select dense, mature, or old forests for nesting and roosting. High-severity fire transforms such forests into a unique forest type known as “snag forest habitat”, which the owls select for foraging. This habitat is disproportionately targeted by post-fire logging projects. Numerous recent articles have explored the influence of high-severity fire and post-fire logging on this species. Studies have shown that post-fire logging significantly reduces Spotted Owl occupancy, but efforts have generally not been made to disentangle the effects of such logging from the influence of high-severity fire alone on Spotted Owls. We conducted an assessment of published, peer-reviewed articles reporting adverse impacts of high-severity fire on Spotted Owls, exploring the extent to which there may have been confounding factors, such as post-fire logging. We found that articles reporting adverse impacts of high-severity fire on Spotted Owls were pervasively confounded by post-fire logging, and in some cases by a methodological bias. Our results indicate a need to approach analyses of high-severity fire and Spotted Owls differently in future research.
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Slobodník, Vladimír, and Roman Slobodník. "The summary on raptors and owls ringing in Slovakia in 2009." Slovak Raptor Journal 4, no. 1 (January 1, 2010): 109–13. http://dx.doi.org/10.2478/v10262-012-0053-z.
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The summary on raptors and owls ringing in Slovakia in 2009The article provides basic information about the number, species and recoveries of ringed birds of prey and owl species in Slovakia in 2009. The report follows similar papers from the following periods: 2002-2004, 2005-2006 and 2007-2008. In 2009 a total of 1,222 individuals were ringed in Slovakia, of which 856 individuals were birds of prey (18 species) and 366 individuals were owls (8 species). From the total number, 719 birds of prey and 257 owl nestlings were ringed. In comparison with the previous year the number of ringed birds of prey and owls increased by 43%.
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Orth, Patricia B., and Patricia L. Kennedy. "Do land-use patterns influence nest-site selection by burrowing owls (Athene cunicularia hypugaea) in northeastern Colorado?" Canadian Journal of Zoology 79, no. 6 (June 1, 2001): 1038–45. http://dx.doi.org/10.1139/z01-071.
Full textAbstract:
Populations of western burrowing owls (Athene cunicularia hypugaea) are declining. In the Great Plains this decline maybe related to a decline in black-tailed prairie dog (Cynomys ludovicianus) towns that the owls use for nest sites. One potential cause of prairie dog decline is conversion of native prairie to agriculture. We predicted that owl-occupied prairie dog towns would be in less fragmented landscapes that contain more prairie then owl-unoccupied prairie dog towns. To test this prediction, we used a geographic information system and spatial analysis metrics to examine the landscape within 1000 and 2500 m radius circles surrounding prairie dog towns in the shortgrass prairie in northeastern Colorado. We compared landscape features of irrigated cropland, non-irrigated cropland, and shortgrass patches around owl-unoccupied (N = 7) and owl-occupied (N = 15) prairie dog towns at these two spatial scales. Contrary to our predictions, at the 2500-m scale burrowing owls prefer to nest in towns surrounded by a landscape in which shortgrass patches were a smaller percentage of the total landscape, relatively far apart from other shortgrass patches, and more numerous then crop patches. At the 1000-m scale owls nested in towns in which shortgrass patches were a smaller percentage of the total surrounding landscape. In Logan County owls may select nest sites in prairie dog towns in more fragmented landscapes because prey availability maybe higher than in less fragmented landscapes and (or) prairie dog control programs may be more active on shortgrass rangelands than in croplands. In addition, the level of fragmentation in our study area (62% of the study area is occupied by native grassland) may not be high enough to have negative consequences on nest occupancy of burrowing owls. However, it is difficult to generalize about the effects of landscape fragmentation on burrowing owls because any effects are probably a complex function of local habitat structure, landscape structure, and local prey and predator availability.
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Kucherenko, Volodymyr, and Pavel Kalinovsky. "Winter Roost Tree Selection and Phenology of the Long-Eared Owl (Asio otus) in Crimea." Diversity 10, no. 4 (September 27, 2018): 105. http://dx.doi.org/10.3390/d10040105.
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The winter roost of the long-eared owl Asio otus in Crimea (South of Ukraine), located in Simferopol, is described. In 2015–2017, the number of long-eared owls varied on a convex curve, with the maximum reached at the end of November and in December. The birds exhibited a strong preference for roosting in conifers, where we recorded 89% of the owls. There was an inverse relationship between the mean of the maximum daily temperature (°C) and the number of owls in both seasons. The owls were not sensitive to abrupt but short-term temperature changes, but the temperature decrease curve caused practically synchronous changes in the dynamics of bird numbers. It was found that the number of owls significantly differed based on weather conditions in 16 trees. The proportion of owls sitting on coniferous trees increased with unfavourable weather, and the converse pattern was observed for deciduous trees.
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Kelly, Elizabeth G., and Eric D. Forsman. "Recent Records of Hybridization Between Barred Owls (Strix Varia) and Northern Spotted Owls (S. Occidentalis Caurina)." Auk 121, no. 3 (July 1, 2004): 806–10. http://dx.doi.org/10.1093/auk/121.3.806.
Full textAbstract:
Abstract We summarized records of hybridization between Barred Owls (Strix varia) and Northern Spotted Owls (S. occidentalis caurina) in Washington and Oregon through 1999. A total of 47 hybrids were observed, including 17 F1s that were first detected as adults, 4 F1s that were banded as juveniles and subsequently recaptured as adults, 10 F1 juveniles, and 16 F2 juveniles. All confirmed cases of hybridization between Barred and Spotted owls involved male Spotted Owls paired with female Barred Owls. Ten F1 hybrids that backcrossed with Barred Owls produced a total of 15 young; 6 F1 hybrids that backcrossed with Spotted Owls produced only 1 young. Those differences may indicate that some combinations of sex and species are more compatible or more fertile than others, but more documentation is needed. Because F2 hybrids and subsequent generations are difficult to distinguish in the field from Barred or Spotted owls, genetic comparisons of blood or tissue samples may be needed to identify hybrids beyond the first generation. The small number of F1 hybrids detected during many years of extensive banding studies of Spotted Owls suggests that the isolating mechanisms that separate Barred and Spotted owls are normally sufficient to avoid hybridization between them. Direct competition between the two species for food and space is probably a much more serious threat to the Spotted Owl than hybridization.
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Heggøy, Oddvar, Tomas Aarvak, Ingar Jostein Øien, Karl-Otto Jacobsen, Roar Solheim, Dan Zazelenchuk, Marten Stoffel, and Oddmund Kleven. "Effects of satellite transmitters on survival in Snowy Owls Bubo scandiacus." Ornis Norvegica 40 (September 18, 2017): 33. http://dx.doi.org/10.15845/on.v40i0.1309.
Full textAbstract:
The use of tracking devices to monitor birds is extensive, but the effects of such instruments on equipped individuals are still insufficiently taken into account. Here we evaluate potential effects of backpack-mounted satellite transmitters (platform terminal transmitters; PTTs) on survival of 28 Snowy Owls Bubo scandiacus. Six confirmed deaths were all probably related to natural and human-induced causes. Although PTT operational time was significantly shorter than expected lifetime of Snowy Owls, five owls were observed alive after transmissions ceased. Additionally four PTTs stopped due to low battery levels, indicating end of transmitter life and not owl mortality. We found no evidence of mortality caused by PTTs, but sample sizes are relatively low and detrimental effects on equipped Snowy Owls cannot be excluded. We recommend caution when instrumenting large owls.
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Slobodník, Vladimír, and Roman Slobodník. "Summary on the ringing of raptors and owls in Slovakia in 2010." Slovak Raptor Journal 5, no. 1 (January 1, 2011): 131–35. http://dx.doi.org/10.2478/v10262-012-0060-0.
Full textAbstract:
Summary on the ringing of raptors and owls in Slovakia in 2010This paper presents brief information on the number, species and recoveries of ringed birds of prey and owls in Slovakia in 2010. It follows similar papers from 2002-2004, 2005-2006, 2007-2008 and 2009. In 2010 a total of 552 individual birds of prey and owls were ringed in Slovakia, of which 405 were birds of prey (16 species) and 147 owls (9 species). From the total number ringed, 327 birds of prey and 85 owl were nestlings. In comparison with the previous year (2009) the number of ringed birds decreased by 55%.
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Rodríguez-Estrella, Ricardo, and Aleyda Peláez Careaga. "The western screech-owl and habitat alteration in Baja California: a gradient from urban and rural landscapes to natural habitat." Canadian Journal of Zoology 81, no. 5 (May 1, 2003): 916–22. http://dx.doi.org/10.1139/z03-062.
Full textAbstract:
We studied the western screech-owl (Otus kennicottii) in the desert of the southern Baja California peninsula to determine its status and habitat selection and whether it benefits from moderate human-caused habitat changes. Based on the response to tape-recorded call broadcasts, western screech-owls were more abundant in undisturbed vegetation than in human-altered habitat. In man-made environments, more owls responded in rural than in urban areas; indeed, they were practically absent in urban areas. In natural areas, a total of 1.6 owls/km was estimated in the nonbreeding season and 2.7 owls/km in the breeding season. The most important habitat features selected in natural areas were greater shrub cover in the strata containing shrubs 12 and 23 m high and greater canopy cover of trees >5 m high. In rural areas adjacent to cultivated areas, owls were present in areas with the greatest cover of shrubs 13 m high and a higher density of shrubs. The western screech-owl also occurs at lower densities in rural areas than in natural areas. Towns appear to be avoided in the arid desert of Baja California Sur. Western screech-owls may be still able to persist in rural areas that occupy an intermediate position on the gradient from a functional natural system (desert vegetation) to a completely altered ecological system, urbanized areas.
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Clayton, Kort M., and Josef K. Schmutz. "Is the decline of Burrowing OwlsSpeotyto cuniculariain prairie Canada linked to changes in Great Plains ecosystems?" Bird Conservation International 9, no. 2 (June 1999): 163–85. http://dx.doi.org/10.1017/s0959270900002288.
Full textAbstract:
SummaryWe examined population and ecosystem patterns hoping to inform conservation strategies for Burrowing OwlsSpeotyto cuniculariain Canada. The owls chose moderately to heavily grazed grasslands for nesting and roosting, and avoided cultivated fields. Where grassland patches were isolated in 90% cultivation, owls dispersed later, for shorter distances and less often. Mortality rate during the 5-month study was high (adult ratio 0.45, juveniles 0.55), which may contribute to local declines. Additional mortality may occur on migration and during winter. We extrapolate from local effects (loss of grassland habitat with burrows for roosting, and ~2% “incidental” predation) to suggest that such changes detrimental to the owls occur throughout the central Great Plains ecosystem which the owls occupy year-round. The changes include ecosystem processes such as plant succession, owl dispersal and predation. These changes are likely to be irreversible on a scale that would be required to help this owl. The species may face extinction in Canada, at the northern limit of its range.
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Milchev, Boyan. "Dietary comparison of coexisting barn owl (Tyto alba) and eagle owl (Bubo bubo) during consecutive breeding seasons." Animal Biology 66, no. 2 (2016): 219–28. http://dx.doi.org/10.1163/15707563-00002499.
Full textAbstract:
Coexistence of predator species often depends on behaviours or preferences that result in spatio-temporal reduction of competition. In this study, the diets of coexisting barn owls (Tyto alba) and eagle owls (Bubo bubo) in an agricultural landscape of SE Bulgaria were compared. White-toothed shrews (Crociduraspp.), voles (Microtusspp.) and mice (Musspp.) were the main prey of barn owl (86.3% by number, 81.2% by biomass) with significantly different frequencies in annual diets. The principle biomass (64.8 ± 6.2%) of the significantly different eagle owl annual diets comprised much heavier prey such as white-breasted hedgehog (Erinaceus roumanicus), European hare (Lepus europaeus) and non-passerine birds of wetlands and open habitats. The two owl species preferred and hunted on different prey size groups in the same territory, and this difference explained the low level of food competition (6.0 ± 3.6% diet overlap according to prey biomass). Voles were the only prey of the two owls with significantly different frequencies for the annual diets in intraspecies comparisons. The proportions of voles in both diets showed similar trends during the study. Eagle owl predation on barn owls was slightly affected by their coexisting breeding despite the high levels of food stress of eagle owl. These findings provide insight into how preying habits can predict successful coexistence of potentially competing predator species.
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Avotins, Andris, Andris Avotins, Viesturs Ķerus, and Ainars Aunins. "Numerical Response of Owls to the Dampening of Small Mammal Population Cycles in Latvia." Life 13, no. 2 (February 17, 2023): 572. http://dx.doi.org/10.3390/life13020572.
Full textAbstract:
Strong numerical and functional responses of owls to voles in cyclic environments are well known. However, there is insufficient knowledge from the boreonemoral region in particular, with depleted populations of small mammals. In this study, we describe the dynamics of the small mammal population in Latvia from 1991 to 2016 and link them to owl population characteristics. We used food niche breadth, number of fledglings, and population trends to lay out the numerical response of six owl species to dampened small mammal population cycles. We found temporarily increasing food niche breadth in tawny and Ural owls. There were no other responses in the tawny owl, whereas the breeding performance of three forest specialist species—pygmy, Tengmalm’s, and Ural owls—corresponded to the vole crash years in Fennoscandia. Moreover, the populations of forest specialist owls decreased, and the change in the Ural owl population can be attributed to the depletion of small mammal populations. We found evidence of a carry-over effect in the eagle owl arising from a strong correlation of declining breeding performance with the small mammal abundance indices in the previous autumn. We conclude that dampening of the small mammal population cycles is an important covariate of the likely effects of habitat destruction that needs to be investigated further, with stronger responses in more specialized (to prey or habitat) species.
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Sandoval, Luis, and David R. Wilson. "Local predation pressure predicts the strength of mobbing responses in tropical birds." Current Zoology 58, no. 5 (October 1, 2012): 781–90. http://dx.doi.org/10.1093/czoolo/58.5.781.
Full textAbstract:
Abstract Many birds join cooperative mobbing aggregations and collectively harass predators. Individuals participating in these ephemeral associations benefit by deterring the predator, but also incur energetic costs and increased risk of predation. Explaining the evolution of mobbing is challenging because individuals could prevail by selfishly seeking safety while allowing others to mob. An important step in understanding the evolution of mobbing is to identify factors affecting its expression. The ecological constraints model suggests that animals are more likely to cooperate under adverse environmental conditions, such as when local predation pressure is high. We tested this prediction by comparing the mobbing responses of several species of birds to the local abundance of their primary predator, the ferruginous pygmy-owl Glaucidium brasilianum. We used acoustic playback to elicit mobbing responses in environments where owls were common, uncommon, or rare. Stimuli were either the song of a ferruginous pygmy-owl or the mobbing calls of three of the owl’s common prey species. During each playback, we characterized mobbing responses by noting the number of species and individuals that approached the loudspeaker, as well as the closest approach by any bird. Mobbing responses to both stimuli were strong in locations where Ferruginous Pygmy-owls were common, intermediate where owls were uncommon, and weak where they were rare. This pattern persisted even after controlling for differences in species richness and composition among the three environments. Results support the ecological constraints model and provide strong evidence that intense predation pressure increases the expression of cooperative mobbing in tropical birds.
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Jenness, Jeffrey S., Paul Beier, and Joseph L. Ganey. "Associations between Forest Fire and Mexican Spotted Owls." Forest Science 50, no. 6 (December 1, 2004): 765–72. http://dx.doi.org/10.1093/forestscience/50.6.765.
Full textAbstract:
Abstract In 1993, the US Fish and Wildlife Service listed the Mexican spotted owl (Strix occidentalis lucida) as threatened, in part because of the rising threat to its habitat from stand-replacing wildfires. In 1997, we surveyed 33 owl sites that, in the previous four years, had burned at various levels ranging from light controlled burns to stand-replacing fires. We compared owl occupancy and reproduction in these burned sites to 31 unburned owl sites with similar habitat and topography. Although unburned sites showed higher proportions of both occupancy and reproduction, the negative relationship observed between recent fire occurrence and owl occupancy rank was statistically weak (Test for Marginal Homogeneity, P = 0.110). Owls tended not to be present where pure pine stands (Pinus spp.) comprised a large proportion (38–85%) of burned sites, but no other factors relating to habitat or fire severity had a significant, biologically interpretable influence on occupancy rank. We suspect that relatively low-intensity ground fires, including most prescribed fires, probably have little or no short-term impact on Mexican spotted owl presence or reproduction, but we have no data on long-term effects of fire. We recommend proactive fuels-management treatments in areas not currently occupied by owls as a means of reducing fire risk in areas occupied by owls. Within areas occupied by owls, judicious treatments may be appropriate after case-by-case evaluations of potential benefits and risks within those sites. FOR. SCI. 50(6):765–772.
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Koivunen, Vesa, Erkki Korpimäki, Harri Hakkarainen, and Kai Norrdahl. "Prey choice of Tengmalm's owls (Aegolius funereus funereus): preference for substandard individuals?" Canadian Journal of Zoology 74, no. 5 (May 1, 1996): 816–23. http://dx.doi.org/10.1139/z96-094.
Full textAbstract:
Errington proposed that predators mainly kill substandard prey, because dominant individuals force subordinate ones into poor habitats, where the predation risk is higher. We studied the prey choice of breeding male Tengmalm's owls (Aegolius funereus funereus) in 1992, when vole densities crashed. We trapped small mammals in the main habitat types in 21 owl territories, and simultaneously identified prey items cached by the same owls in their nest boxes. The main prey of owls in western Finland are the common vole (Microtus epiroticus), field vole (M. agrestis), bank vole (Clethrionomys glareolus), and common shrew (Sorex araneus). Common voles were the preferred prey of owls, followed by field voles, bank voles, and common shrews. Prey captured by owls tended to be lighter and smaller than those available in the field. This tendency was significant for field voles and common shrews. Field voles, common voles, and female common shrews captured by owls tended to have more internal fat than those available in the field. This tendency was significant for male field voles and female common shrews. Owls appeared to choose small individuals of some, but not all, prey species, and that these prey items were not in poor physiological condition.
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Wiens, J. David, Katie M. Dugger, J. Mark Higley, Damon B. Lesmeister, Alan B. Franklin, Keith A. Hamm, Gary C. White, et al. "Invader removal triggers competitive release in a threatened avian predator." Proceedings of the National Academy of Sciences 118, no. 31 (July 19, 2021): e2102859118. http://dx.doi.org/10.1073/pnas.2102859118.
Full textAbstract:
Changes in the distribution and abundance of invasive species can have far-reaching ecological consequences. Programs to control invaders are common but gauging the effectiveness of such programs using carefully controlled, large-scale field experiments is rare, especially at higher trophic levels. Experimental manipulations coupled with long-term demographic monitoring can reveal the mechanistic underpinnings of interspecific competition among apex predators and suggest mitigation options for invasive species. We used a large-scale before–after control–impact removal experiment to investigate the effects of an invasive competitor, the barred owl (Strix varia), on the population dynamics of an iconic old-forest native species, the northern spotted owl (Strix occidentalis caurina). Removal of barred owls had a strong, positive effect on survival of sympatric spotted owls and a weaker but positive effect on spotted owl dispersal and recruitment. After removals, the estimated mean annual rate of population change for spotted owls stabilized in areas with removals (0.2% decline per year), but continued to decline sharply in areas without removals (12.1% decline per year). The results demonstrated that the most substantial changes in population dynamics of northern spotted owls over the past two decades were associated with the invasion, population expansion, and subsequent removal of barred owls. Our study provides experimental evidence of the demographic consequences of competitive release, where a threatened avian predator was freed from restrictions imposed on its population dynamics with the removal of a competitively dominant invasive species.
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Priestley, Lisa Takats. "The Barred Owl, Strix varia in Alberta: Distribution and Status." Canadian Field-Naturalist 118, no. 2 (April 1, 2004): 215. http://dx.doi.org/10.22621/cfn.v118i2.916.
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Barred Owl distribution and status in Alberta were investigated using over 300 individual records (1912 through 1999) that were collected from literature, museum/zoo specimens, nest cards, bird surveys, volunteer raptor banders, and naturalists. Barred Owls were distributed throughout much of the boreal forest, aspen parkland, foothill, and mountain ecoregions of Alberta. Fifty-four breeding records (46 nests) were found. Barred Owls were associated with older forests and had a clumped distribution, predominantly along water where larger Balsam Poplar trees provide nesting sites. According to Alberta's "Status of Alberta Wildlife 2000" criteria, the Barred Owl should be assessed as Sensitive. There is no evidence that Barred Owls have expanded their range in Alberta in the last 100 years; rather, they have maintained their distribution.
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Galloway, Terry D., and Robert J. Lamb. "Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada." Canadian Entomologist 151, no. 5 (July 31, 2019): 608–20. http://dx.doi.org/10.4039/tce.2019.42.
Full textAbstract:
AbstractEleven of the 12 species of owls (Aves: Strigidae, Tytonidae) known to occur in Manitoba, Canada, were examined for chewing lice (Phthiraptera: Amblycera, Ischnocera) from 1976 to 2015: barn owl (Tyto alba (Scopoli); Aves: Tytonidae) (n = 2), snowy owl (Bubo scandiacus (Linnaeus); Aves: Strigidae) (n = 77), great horned owl (Bubo virginianus (Gmelin); Aves: Strigidae) (n = 262), great grey owl (Strix nebulosa Förster; Aves: Strigidae) (n = 142), barred owl (Strix varia Barton; Aves: Strigidae) (n = 10), northern hawk owl (Surnia ulula (Linnaeus); Aves: Strigidae) (n = 18), short-eared owl (Asio flammeus (Pontoppidan); Aves: Strigidae) (n = 74), long-eared owl (Asio otus (Linnaeus); Aves: Strigidae) (n = 67), eastern screech owl (Megascops aslo (Linnaeus); Aves: Strigidae) (n = 59), boreal owl (Aegolius funereus (Linnaeus); Aves: Strigidae) (n = 47), and northern saw-whet owl (Aegolius acadicus (Gmelin); Aves: Strigidae) (n = 44), a total of 802 owls. No lice were found infesting barn owl (Tyto alba (Scopoli); Aves: Tytonidae) or eastern screech owl (Megascops asio (Linnaeus); Aves: Strigidae). We collected a total of 113 810 lice of 12 species: Kurodaia Uchida (Phthiraptera: Menoponidae) – three species; and Strigiphilus Mjöberg (Phthiraptera: Philopteridae) – nine species. Overall prevalence of infestation ranged from 10.0% to 88.9%. Mean intensity for total lice ranged from 22.4 to 506.5. Infestation parameters for each louse–host combination are provided; prevalence and mean intensity were not related for louse–host species combinations. Distribution of louse infestations was highly aggregated. In all louse–host combinations but one, either females were more prevalent than males or there was no significant deviation from 50:50. Male Strigiphilus ceblebrachys Denny significantly outnumbered females in snowy owls. There was a tendency for louse species to co-occur on the same host specimen. Where sample sizes for owls were large enough, no seasonal patterns in abundance of lice were detected.
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Hipkiss, T., O. Stefansson, and B. Hörnfeldt. "Effect of cyclic and declining food supply on great grey owls in boreal Sweden." Canadian Journal of Zoology 86, no. 12 (December 2008): 1426–31. http://dx.doi.org/10.1139/z08-131.
Full textAbstract:
In this study of 35 years of data, we examine the short-term (cyclic) and long-term relationship between breeding success of great grey owls ( Strix nebulosa Forster, 1772) and their food supply (bank voles ( Clethrionomys glareolus (Schreber, 1780)), grey-sided voles ( Clethrionomys rufocanus (Sundevall, 1846)), and field voles ( Microtus agrestis (L., 1761))) in northern Sweden. Annual number of owl nests showed a 3 year cyclicity, which as predicted, corresponded to the length of the vole cycle in the region. Mean annual brood size also fluctuated and was positively dependent on the vole supply during the same spring. In this region, there has also been a decline in vole numbers in recent decades, from high-amplitude cycles in the 1970s to subsequent low-amplitude cycles. Correspondingly, and as predicted, mean annual brood size of the owls also declined, although only during the third years of the vole cycle when vole supply in spring and brood size of the owls is at its highest level in high-amplitude cycles. We predict that in the long run the vole decline, associated with increasingly milder winters, and the reduction of the brood size of the owls, especially in years of high owl breeding success, will have serious implications for the population of great grey owls in Scandinavia.
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Lindner, Martin. "Influence of the Eagle Owl (Bubo bubo) on the Peregrine Falcon (Falco peregrinus) population in Germany." Ornis Hungarica 26, no. 2 (December 1, 2018): 243–53. http://dx.doi.org/10.1515/orhu-2018-0032.
Full textAbstract:
Abstract In Germany, the Eagle Owl is the only animal species that has a massive impact on the distribution and breeding success of the Peregrine Falcon. Both species compete for the same breeding sites on rocks. In addition, the Peregrine Falcon belongs to the prey spectrum of the Eagle Owl. The Eagle Owl always dominates at places where the two species meet. Since the 1980s, the Eagle Owl has taken over many of the rock face breeding sites of the Peregrine Falcon in Germany. This trend towards the taking-over of Peregrine Falcon nesting sites is ongoing in areas with rocks, as not all regions of Germany have yet been completely colonized by Eagle Owls. Since 1975, the Eagle Owl initially nested on buildings in rural areas, but it is now also colonizing urban areas. Eagle Owls are more and more frequently taking over Peregrine Falcon nest boxes on buildings. The currently growing Peregrine Falcon breeding population on buildings is expected to decline in coming years due to predation by the Eagle Owl, even though these owls do not breed very successfully on buildings and many old and young owls are killed. These statements apply to large parts of Germany. In other areas of Europe, the future usage of buildings as Eagle Owl breeding sites can be expected to have an impact on the Peregrine Falcon populations there. At least eight other Peregrine Falcon breeding sites on buildings and rocks have been taken over by Egyptian Geese (Alopochen aegyptiaca).
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Munroe, Robert L., and Mary Gauvain. "Owls, Climates, and Experts." Journal of Cognition and Culture 18, no. 1-2 (March 28, 2018): 66–88. http://dx.doi.org/10.1163/15685373-12340020.
Full textAbstract:
Abstract The cognitive research of Atran and Medin (2008) plus preliminary cross-cultural inquiry about owls permitted the formulation of a hypothesis: Inhabitants of cold-climate societies were likely to be, in relative terms, “experts” on owls. Subsequent cross-cultural study (N = 56) affirmed that in cold-climate societies, in contrast to others, the habits and characteristics of owls were more frequently noted, these birds were more often used functionally (especially for feather-ornamentation), and the human inhabitants of cold-climate areas manifested fewer negative supernaturalistic interpretations of owl behavior. For the sample as a whole, however, some form of magico-religious belief — usually negative, such as association of owls with witchcraft — exceeded all other practices and concepts, including functional uses and ethnozoological descriptions of owls. The importance of taking affective factors into account in cross-cultural cognitive research was emphasized. Exploratory analysis also revealed that owls were of extraordinarily high interest to Native North Americans, and reasons for this regularity were considered. The paper concludes with discussion of the relation between ecological setting and cultural conceptions of the natural world.
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Benavides, Pelayo, and José Tomás Ibarra. "“Uncanny Creatures of the Dark.”." Anthropos 116, no. 1 (2021): 163–76. http://dx.doi.org/10.5771/0257-9774-2021-1-163.
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Belief systems of human societies are deeply related with animals, which are symbolised in traditional narratives. Here we review reported cases from around the world and our own ethnographic observations from southern Chile, to analyse beliefs associated with owls. In particular, we explore the role that owls play in traditional narratives and the likely reasons of their saliency, including their connections with the extraordinary. For the latter, we utilise the concept of “the uncanny” to analyse how owls generate a feeling of something not simply mysterious but, more specifically, something strangely familiar. Owls trigger unsettling experiences of the “normal,” with the ensuing feelings of unhomeliness, which may explain their saliency across human societies. Finally, we discuss that the uncanny nature of owls is precisely what locates them in a culturally stimulating position and what should be considered by conservationists and politicians to tackle a more integrative approach to owl conservation.
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Seamans, Mark E., R. J. Gutiérrez, and Christopher A. May. "Mexican Spotted Owl (Strix Occidentalis) Population Dynamics: Influence of Climatic Variation on Survival and Reproduction." Auk 119, no. 2 (April 1, 2002): 321–34. http://dx.doi.org/10.1093/auk/119.2.321.
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Abstract Understanding the mechanisms causing temporal variability in demographic parameters is essential to understanding fluctuations in populations. As part of a long-term demographic study, we evaluated influence of climate on Mexican Spotted Owl (Strix occidentalis lucida) annual survival and reproduction in two study areas, one in Arizona and one in New Mexico. Spotted Owl survival in New Mexico and reproductive output in both study areas were positively related to total amounts of precipitation from the previous year, previous winter, or monsoon season. For both study areas, temporal process variation in reproductive output (CV[R] = 51.2 and 75.2% for Arizona and New Mexico, respectively) was greater than that for survival (CV[ϕ] = 12.9 and 7.1% for Arizona and New Mexico, respectively). Precipitation from the previous year explained 73% of σ̂2temporal reproductive output for Arizona owls and precipitation from the previous monsoon explained 42% of σ̂2temporal in reproductive output for New Mexico owls. Precipitation from the previous monsoon season explained 53% of σ̂2temporal in Arizona owl survival and precipitation from the previous winter explained 56% of σ̂2temporal in New Mexico owl survival. The two populations of Spotted Owls we studied appeared to have the same life-history strategy hypothesized for a population of Northern Spotted Owls (S. o. caurina), although the Mexican subspecies apparently responded quite differently to climatic variation.
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Whalen, David M., and Bryan D. Watts. "Annual Migration Density and Stopover Patterns of Northern Saw-whet Owls (Aegolius acadicus)." Auk 119, no. 4 (October 1, 2002): 1154–61. http://dx.doi.org/10.1093/auk/119.4.1154.
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Abstract Northern Saw-whet Owls (Aegolius acadicus) exhibit large fluctuations in annual number of individuals migrating in eastern United States. Underlying large differences in the magnitude of the migration may be important density-dependent effects on body condition and stopover patterns. We investigated such effects using data from saw-whet owls that were trapped and banded during autumn migration at the southern tip of the Delmarva Peninsula (near Cape Charles, Virginia) from 1994 to 2000. Irruptive migration events occurred in 1995 and 1999 when 1,002 and 700 owls were captured, respectively. Capture totals ranged from 22 to 105 owls during five nonirruptive years. Irruptive migration years were dominated by immature owls (82% of captures) and were characterized by low recapture rates (13%) and shorter minimum stopover lengths (median = 5 nights) for all owls. Body masses and body-condition index scores were significantly lower for both immature and adult age classes during years when owl density was very high. During such years, a smaller percentage of owls elected to stopover and, among those that did, individuals in good condition departed sooner than individuals in poor condition. Conversely, during nonirruptive years, adults constituted 67% of captures, recapture rates were nearly 3× higher (35%), and stopover lengths were twice as long (median = 10 nights). Recapture rates were significantly higher for adults (43%) than for immature owls (23%) and initial body condition of adults was positively correlated with their length of stopover. During light migration years, conditions may be conducive for extended residency, particularly for adult owls in good condition. Our results suggest that density-dependence is an important mechanism driving migration and stopover patterns of saw-whet owls.
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Tulis, Filip, Michal Ševčík, and Ján Obuch. "Long-eared owls roosted in the forest, still hunted in open land." Raptor Journal 13, no. 1 (December 1, 2019): 105–19. http://dx.doi.org/10.2478/srj-2019-0003.
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Abstract Long-eared owls’ winter roosts located within forest, compared to their winter roosts in human settlements, often escape human attention. Only minimum information has been published about winter roosts located deep in the forest. During the years 2005 to 2016, we collected long-eared owl pellets at irregularly occupied forest winter roosts. Compared to the diet at winter roosts in human settlements, the long-eared owls roosting in the forest surprisingly significantly more frequently hunted the common vole. Moreover, we did not record higher consumption of forest mammal species in the diet of owls at forest winter roosts. Long-eared owls roosting in human settlements hunted significantly more birds. The results show that, despite the location of deep forest winter roosts, long-eared owls preferred hunting the common vole, i.e. hunting in open agricultural land. The study also points out the lack of knowledge about winter roosts located deep in the forest.
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Obuch, Ján. "On the diet of owls (Strigiformes) in Jordan." Slovak Raptor Journal 12, no. 1 (December 1, 2018): 9–40. http://dx.doi.org/10.2478/srj-2018-0003.
Full textAbstract:
Abstract Between 2005 and 2015 I undertook eight trips to Jordan during which I collected pellets from seven owl species. In them 14,203 food items were identified. Mammals (Mammalia, 46 species, 37.9% of prey items) formed the most numerous component, invertebrates (Evertebrata) made up 33.4%, birds (Aves, 25.4%) were represented with at least 104 species, reptiles (Reptilia) came to 3.2%, and two species of amphibian were identified (Amphibia, 0.2%). Pharoah eagle owls (Bubo ascalaphus) and Byzantine eagle owls (Bubo bubo interpositus) primarily hunt larger mammals and birds, although Agamidae and Scorpiones were also represented more frequently among B. ascalaphus. Mammals predominated among tawny owls (Strix aluco wilkonskii) (Mammalia, 58.9%), mainly the eastern rock mouse (Apodemus mystacinus) (24.9%). For wintering long-eared owls Asio otus otus the most important food was small birds (Aves, 78.3%), especially house sparrows (Passer domesticus), Fringillidae and Sylviidae. For barn owls (Tyto alba erlangeri) the principal prey was small mammals (83.1%), mainly mice (Mus sp.), Günther’s vole (Microtus guentheri), grey hamster (Cricetulus migratorius) and shrews (Soricidae). Hume’s tawny owl (Strix butleri) pellets contained mostly invertebrates (58.9%) and lizards, and their most frequent mammal prey were Wagner’s gerbil (Gerbillus dasyurus) and spiny mice (Acomys sp.). There was an even higher propostion of invertebrates (86.4%) among lilith owlets (Athene lilith). In addition to the insect orders Coleoptera, Orthoptera and Hymenoptera, remains of Scorpiones and Solifugae were also frequently found. The summarized results from individual owl species are compared with those gathered by the author in the surrounding Middle Eastern countries: Israel, Syria, Lebanon and Egypt.