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1
Leonard, Marty L., e Jaroslav Picman. "Why Are Nesting Marsh Wrens and Yellow-Headed Blackbirds Spatially Segregated?" Auk 103, n. 1 (1 gennaio 1986): 135–40. http://dx.doi.org/10.1093/auk/103.1.135.
Testo completoAbstract (sommario):
Abstract The activity centers of Marsh Wrens (Cistothorus palustris) and Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) are spatially segregated. This segregation may occur because (1) one species excludes the other or (2) the two species prefer different habitats. These hypotheses were tested by documenting changes in the size and location of Marsh Wren territories throughout the breeding season, and by the removal of conesting Yellow-headed Blackbirds. The expansion of Marsh Wren territories into blackbird breeding areas after both the natural departure and the removal of blackbirds best supports the explanation based on the active exclusion of Marsh Wrens by Yellow-headed Blackbirds.
2
Rząd, I., J. Sitko, R. Sałamatin e D. Wysocki. "Helminth community structure study on urban and forest blackbird (Turdus merula L.) populations in relation to seasonal bird migration on the south Baltic Sea coast (NW Poland)". Helminthologia 51, n. 2 (1 giugno 2014): 117–29. http://dx.doi.org/10.2478/s11687-014-0219-6.
Testo completoAbstract (sommario):
Abstract The aim of the study was to compare helminth community structure of urban and forest blackbird populations. 24 helminth species in 98 blackbirds were found. Higher species richness was noted in the forest population of the blackbird (23 species) in comparison to the urban population (14 species). The response of the helminth fauna to a synanthropic habitat, contrary to a natural habitat, consists in a significant reduction in most parasitological parameters. Higher species richness has been noted in spring (17 species) than in autumn (14 species). Urban habitat, in contrast to the forest, may cause changes in the abundance of helminth communities in male and female blackbirds. The helminth fauna of nestlings, in spite of low species richness is characterized by a higher prevalence and intensity of infection in comparison to blackbirds feeding on their own. Helminth fauna of the blackbird seems to be a good indicator of environmental quality.
3
Clark, Robert G., e Patrick J. Weatherhead. "The effect of fine-scale variations in agricultural land use on the abundance of red-winged blackbirds". Canadian Journal of Zoology 64, n. 9 (1 settembre 1986): 1951–55. http://dx.doi.org/10.1139/z86-293.
Testo completoAbstract (sommario):
We used censuses of breeding red-winged blackbirds (Agelaius phoeniceus) and of land use to test the prediction that blackbirds should be most abundant where there is a mix of hayfield (breeding habitat) and corn production (feeding habitat) but fewer birds where either habitat predominates. Red-winged blackbird abundance increased in response to increases in both hayfields and cropland. Multivariate analysis including hayfield, cropland, and wetland abundance as explanatory variables explained substantially more variation in blackbird abundance than any of the variables could by themselves. Although our analyses indicated some evidence of a decline in numbers of blackbirds when either hayfields or cropland became very abundant, none of the areas censused approached true monoculture and therefore the conditions under which a sharp decline in the blackbird population was predicted were not encountered. However, evidence from other locations and local population trends suggest that the prediction is correct.
4
Picman, Jaroslav, Stanislav Pribil e Andre Isabelle. "Antipredation Value of Colonial Nesting in Yellow-Headed Blackbirds". Auk 119, n. 2 (1 aprile 2002): 461–72. http://dx.doi.org/10.1093/auk/119.2.461.
Testo completoAbstract (sommario):
Abstract Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) in Manitoba breed in dense colonies in cattail marshes. Their reproductive success is affected mainly by predation. The most important predator on blackbird nests is the Marsh Wren (Cistothorus palustris), which breaks blackbird eggs and kills small nestlings. We examined whether colonial nesting in Yellow-headed Blackbirds may represent an adaptation to reduce Marsh Wren predation. Marsh Wren predation may be reduced by (1) mutual nest defense by adult blackbirds, (2) predator satiation or dilution, or (3) selfish-herd effects. We tested these hypotheses using experimental nests and found that their safety increased with decreasing distance to the nearest blackbird nest and with increasing density of simultaneously active blackbird nests located nearby. Safety also was higher for nests placed inside a blackbird colony rather than outside. These findings support the nest-defense hypothesis. We also found that Marsh Wrens are capable of destroying a whole blackbird colony in a few days, and that colony size is not correlated with nest safety. These results suggest that the satiation or dilution benefits are negligible. Finally, we found that central nests are safer than peripheral nests in a blackbird colony, but not in an artificial colony, providing weak support for the selfish-herd hypothesis. We conclude that nest predation is reduced mainly by mutual nest defense of adult birds and may represent an important selective force favoring colonial nesting in this species.
5
Sakhvon, Vital V. "NESTING FEATURES OF BLACKBIRD (TURDUS MERULA) IN URBAN GREEN SPACES IN MINSK". Journal of the Belarusian State University. Ecology., n. 4 (25 dicembre 2021): 46–53. http://dx.doi.org/10.46646/2521-683x/2021-4-46-53.
Testo completoAbstract (sommario):
Synurbic populations of birds are characterized by specific features that differ from those of wild populations of the same species, which is the result of adaptation to living in cities. The paper analyses some parameters of breeding of the Blackbird (Turdus merula) in two park in Minsk and compares them with the breeding biology of wild Blackbirds in natural habitats. During the years 2015-2017 and 2019-2021, 74 nests of urban Blackbird were obtained. For comparison, data on 245 nest of this species in natural landscapes were used.As a result, it was found that the nest selection in urban Blackbirds remains similar to wild Blackbirds in forests, and the differences are explained by the peculiarities of forestry activities carried out in urban parks. More than 74 % of all nests were built in the undergrowth layer, while most of the nests were located on the Norway spruce (59.72 %). A majority of urban Blackbirds started laying first eggs relatively later (from 21.04 to 10.05) than forest birds (from 11.04 to 30.04), which most likely results from the adaptation of birds to a significant recreational load from humans during the period when the trees have not come into leaf yet. Nevertheless, no differences were found in the average clutch size between urban (4.17 ± 0.72 eggs) and forest (4.51 ± 0.64 eggs) birds. The low breeding success of the Blackbird (39.4 %) in the urbanized area testifies to the fact that the homeostasis of the relatively high number of the urban Blackbird population in Minsk is most likely maintained due to the constant influx of individuals from local suburban forests.
6
PARFITT, DAN E., e GREGORY J. FOX. "GENETIC SOURCES OF RESISTANCE TO BLACKBIRD PREDATION IN SUNFLOWER". Canadian Journal of Plant Science 66, n. 1 (1 gennaio 1986): 19–23. http://dx.doi.org/10.4141/cjps86-003.
Testo completoAbstract (sommario):
Fifty-one sunflower (Helianthus annuus L.) inbreds were grown at three environments (locations) in North Dakota. Inbreds at two locations were subjected to naturally occurring bird predation by redwinged blackbirds (Agelaius phoeniceus L.) and yellowheaded blackbirds (Xanthocephalus xanthocephalus Bonaparte). The third sunflower plot was surrounded by a cage into which redwinged blackbirds were introduced. Bird damage was estimated as percent achenes removed from individual sunflower heads. Significant differences among environments were observed (P < 0.01). However, genotype performance among environments was highly correlated (P < 0.01). Half sib progeny from 36 of these inbreds were grown along with their maternal inbred parents to estimate narrow sense heritability (h2NS) of resistance to bird predation. Estimates of h2NS obtained by parent offspring regression and by covariance among half-sib families were h2NS = 0.69 and h2NS = 0.66, respectively. These estimates indicate a 67% level of heritability for resistance to bird predation, and suggest that it should be possible to develop sunflower lines with improved resistance.Key words: Sunflower, bird feeding, redwinged blackbird, yellowheaded blackbird
7
Wang, Yanping, Qin Huang, Sisi Lan, Qin Zhang e Shuihua Chen. "Common blackbirds Turdus merula use anthropogenic structures as nesting sites in an urbanized landscape". Current Zoology 61, n. 3 (1 giugno 2015): 435–43. http://dx.doi.org/10.1093/czoolo/61.3.435.
Testo completoAbstract (sommario):
Abstract The common blackbird Turdus merula is one of the most highly urbanized bird species. However, to date, the use of anthropogenic structures as nesting sites in the common blackbird is rarely documented, and the factors influencing its use of the anthropogenic structures as nesting sites remain unclear. In this study, we systematically quantified and determined the factors influencing the use of anthropogenic structures as nesting sites in common blackbirds in a highly urbanized city of Hangzhou, China. We searched for nests of common blackbirds during four breeding seasons from 2010 to 2013. Among the 60 nests found, 34 nests were in anthropogenic structures such as wall ledges, air condition mounts, window canopies, cable poles, guardrails, eaves, balcony frames, flowerpots and flower shelves on balconies. We found that the available anthropogenic nest sites and the available nesting trees were main factors determining the use of anthropogenic structures as nesting sites in common blackbirds. In urban environments, the amount of available anthropogenic nesting sites increased significantly, whereas the number of natural nesting sites reduced greatly. Our results suggest that common blackbirds can adjust their nest sites in response to urbanization and such nesting behavior shifts may aid them to colonize urban environments. From a management viewpoint, our results indicate that behavioral flexibility should be taken into account for effective urban wildlife management and conservation.
8
Hönig, Vaclav, Martin Palus, Tomas Kaspar, Marta Zemanova, Karolina Majerova, Lada Hofmannova, Petr Papezik et al. "Multiple Lineages of Usutu Virus (Flaviviridae, Flavivirus) in Blackbirds (Turdus merula) and Mosquitoes (Culex pipiens, Cx. modestus) in the Czech Republic (2016–2019)". Microorganisms 7, n. 11 (16 novembre 2019): 568. http://dx.doi.org/10.3390/microorganisms7110568.
Testo completoAbstract (sommario):
Usutu virus (USUV) is a flavivirus (Flaviviridae: Flavivirus) of an African origin transmitted among its natural hosts (diverse species of birds) by mosquitoes. The virus was introduced multiple times to Europe where it caused mortality of blackbirds (Turdus merula) and certain other susceptible species of birds. In this study, we report detection of USUV RNA in blackbirds, Culex pipiens and Cx. modestus mosquitoes in the Czech Republic, and isolation of 10 new Czech USUV strains from carcasses of blackbirds in cell culture. Multiple lineages (Europe 1, 2 and Africa 3) of USUV were found in blackbirds and mosquitoes in the southeastern part of the country. A single USUV lineage (Europe 3) was found in Prague and was likely associated with increased mortalities in the local blackbird population seen in this area in 2018. USUV genomic RNA (lineage Europe 2) was detected in a pool of Cx. pipiens mosquitoes from South Bohemia (southern part of the country), where no major mortality of birds has been reported so far, and no flavivirus RNA has been found in randomly sampled cadavers of blackbirds. The obtained data contributes to our knowledge about USUV genetic variability, distribution and spread in Central Europe.
9
Langston, Lee S. "Powering Out of Trouble". Mechanical Engineering 135, n. 12 (1 dicembre 2013): 36–41. http://dx.doi.org/10.1115/1.2013-dec-3.
Testo completoAbstract (sommario):
This article presents a study of Pratt & Whitney’s J58, till date the best and high-powered engine for manufacturing lessons required for the development of F35 Joint Strike Fighter. The J58 Blackbird engine is a variable cycle engine, a turbojet/ramjet combined-cycle engine. It is a conventional afterburning turbojet for take-off and transonic flight, and it approximates a ramjet during high-speed supersonic cruise. The power plant for the Blackbirds is a marvelous development on the part of Pratt & Whitney, as it is the only engine of its kind in the world. The noise and vibration from a J58 test was so great that it could rattle the side-view mirror off nearby cars. The engine was developed at an isolated research center in Florida. At take-off and low-speed flight, the J58 engine/afterburner provides most of the thrust. Both of the Blackbird’s twin nacelles contain an engine supersonic inlet, the J58 engine with its afterburner, and an exhaust ejector nozzle. All three components contribute to the Blackbird’s propulsive thrust in varying proportions, depending on flight speed.
10
Wohner, Patricia J., Carol R. Foss e Robert J. Cooper. "Rusty Blackbird Habitat Selection and Survivorship during Nesting and Post-Fledging". Diversity 12, n. 6 (2 giugno 2020): 221. http://dx.doi.org/10.3390/d12060221.
Testo completoAbstract (sommario):
Rusty blackbird (Euphagus carolinus) populations have declined dramatically since the 1970s and the cause of decline is still unclear. As is the case for many passerines, most research on rusty blackbirds occurs during the nesting period. Nest success is relatively high in most of the rusty blackbird’s range, but survival during the post-fledging period, when fledgling songbirds are particularly vulnerable, has not been studied. We assessed fledgling and adult survivorship and nest success in northern New Hampshire from May to August in 2010 to 2012. We also assessed fledgling and adult post-fledging habitat selection and nest-site selection. The likelihood of rusty blackbirds nesting in a given area increased with an increasing proportion of softwood/mixed-wood sapling stands and decreasing distances to first to sixth order streams. Wetlands were not selected for nest sites, but both adults and fledglings selected wetlands for post-fledging habitat. Fledglings and adults selected similar habitat post-fledging, but fledglings were much more likely to be found in habitat with an increasing proportion of softwood/mixed-wood sapling stands and were more likely to be closer to streams than adults. No habitat variables selected during nesting or post-fledging influenced daily survival rates, which were relatively low for adults over the 60-day study periods (males 0.996, females 0.998). Fledgling survival rates (0.89) were much higher than reported for species of similar size.
11
Manson, Kathleen K. E., Jenna P. B. McDermott, Luke L. Powell, Darroch M. Whitaker e Ian G. Warkentin. "Assessment of Rusty Blackbird Habitat Occupancy in the Long Range Mountains of Newfoundland, Canada Using Forest Inventory Data". Diversity 12, n. 9 (4 settembre 2020): 340. http://dx.doi.org/10.3390/d12090340.
Testo completoAbstract (sommario):
Rusty blackbirds (Euphagus carolinus), once common across their boreal breeding distribution, have undergone steep, range-wide population declines. Newfoundland is home to what has been described as one of just two known subspecies (E. c. nigrans) and hosts some of the highest known densities of the species across its extensive breeding range. To contribute to a growing body of literature examining rusty blackbird breeding ecology, we studied habitat occupancy in Western Newfoundland. We conducted 1960 point counts across a systematic survey grid during the 2016 and 2017 breeding seasons, and modeled blackbird occupancy using forest resource inventory data. We also assessed the relationship between the presence of introduced red squirrels (Tamiasciurus hudsonicus), an avian nest predator, and blackbird occupancy. We evaluated 31 a priori models of blackbird probability of occurrence. Consistent with existing literature, the best predictors of blackbird occupancy were lakes and ponds, streams, rivers, and bogs. Red squirrels did not appear to have a strong influence on blackbird habitat occupancy. We are among the first to model rusty blackbird habitat occupancy using remotely-sensed landcover data; given the widespread availability of forest resource inventory data, this approach may be useful in conservation efforts for this and other rare but widespread boreal species. Given that Newfoundland may be a geographic stronghold for rusty blackbirds, future research should focus on this distinct population.
12
Pachomski, Amanda, Stacy McNulty, Carol Foss, Jonathan Cohen e Shannon Farrell. "Rusty Blackbird (Euphagus carolinus) Foraging Habitat and Prey Availability in New England: Implications for Conservation of a Declining Boreal Bird Species". Diversity 13, n. 2 (23 febbraio 2021): 99. http://dx.doi.org/10.3390/d13020099.
Testo completoAbstract (sommario):
The Rusty Blackbird (Euphagus carolinus) is an imperiled migratory songbird that breeds in and near the boreal wetlands of North America. Our objective was to investigate factors associated with Rusty Blackbird wetland use, including aquatic invertebrate prey and landscape features, to better understand the birds’ habitat use. Using single-season occupancy modeling, we assessed breeding Rusty Blackbird use of both active and inactive beaver-influenced wetlands in New Hampshire and Maine, USA. We conducted timed, unlimited-radius point counts of Rusty Blackbirds at 60 sites from May to July 2014. Following each point count, we sampled aquatic invertebrates and surveyed habitat characteristics including percent mud cover, puddle presence/absence, and current beaver activity. We calculated wetland size using aerial imagery and calculated percent conifer cover within a 500 m buffer of each site using the National Land Cover Database 2011. Percent mud cover and invertebrate abundance best predicted Rusty Blackbird use of wetlands. Rusty Blackbirds were more likely to be found in sites with lower percent mud cover and higher aquatic invertebrate abundance. Sites with Rusty Blackbird detections had significantly higher abundances of known or likely prey items in the orders Amphipoda, Coleoptera, Diptera, Odonata, and Trichoptera. The probability of Rusty Blackbird detection was 0.589 ± 0.06 SE. This study provides new information that will inform habitat conservation for this imperiled species in a beaver-influenced landscape.
13
Németh, Zoltán. "Partial migration and decreasing migration distance in the Hungarian population of the Common Blackbird (Turdus merula Linnaeus, 1758): Analysis of 85 years of ring recovery data". Ornis Hungarica 25, n. 1 (27 giugno 2017): 101–8. http://dx.doi.org/10.1515/orhu-2017-0007.
Testo completoAbstract (sommario):
Abstract The Common Blackbird is a partial migrant throughout much of its range in Europe. That is, part of its breeding population migrates while the rest stays at the breeding ground for winter. Given the rapidly changing global climate, it is important to understand how migratory birds, including partial migrants, respond to shifting climatic conditions. In this study, I analyzed 85 years of ring recovery data of the Hungarian population of the Blackbird, ringed during the breeding season and recovered during migration or winter, with two objectives in mind: (1) to assess whether the Hungarian Blackbird population is also partially migratory, and (2) to test the prediction that Blackbirds have exhibited decreasing migration distances over the past decades as expected based on warming winter temperatures. Hungarian Blackbirds expressed both migratory and resident strategies, thus can be considered as partial migrants. Furthermore, Blackbirds had been recovered increasingly closer (-5.9 km/year) to their breeding grounds in the past decades. Age and sex had no effects on recovery distance. Provided that this trend continues, the adaptive benefits of migratory behavior may eventually be reduced to a level that selection will not maintain it in the population and the Hungarian population becomes entirely sedentary. Surprisingly, 88% of migrant recoveries were the result of shooting or hunting activities in Mediterranean countries, primarily in Italy, highlighting both the need to understand the effects of hunting pressure on migratory behavior at the population level in songbirds and the urgency to ban the killing of migratory birds in European countries.
14
Edwards, Brandon, Allison Binley, Willow English, Emma Hudgins e Samuel Snow. "A highly anomalous Red-winged Blackbird (<i>Agelaius phoeniceus</i>) song". Canadian Field-Naturalist 136, n. 1 (29 luglio 2022): 1–4. http://dx.doi.org/10.22621/cfn.v136i1.2877.
Testo completoAbstract (sommario):
Red-winged Blackbird (Agelaius phoeniceus) is a highly vocal species with a repertoire of similar, yet acoustically distinct songs. These songs may be altered drastically if, as a nestling, the male goes deaf or becomes acoustically isolated. In deaf Red-winged Blackbirds, these dramatic song alterations may present as songs bearing slight resemblance to the introductory phrase of their normal song. Here, we present a Red-winged Blackbird song observed in Ottawa, Ontario, Canada, that is far outside any normal variation in Red-winged Blackbird songs. Given the individual’s age and the consistency of the anomalous song, it is possible that this is a deaf bird.
15
Carlson, James C., Randal S. Stahl, John J. Wagner, Terry E. Engle, Shelagh T. DeLiberto, Dustin A. Reid e Scott J. Werner. "Nutritional depletion of total mixed rations by red-winged blackbirds and projected impacts on dairy cow performance". Journal of Dairy Research 85, n. 3 (agosto 2018): 273–76. http://dx.doi.org/10.1017/s0022029918000481.
Testo completoAbstract (sommario):
This Research Communication describes an investigation of the nutritional depletion of total mixed rations (TMR) by pest birds. We hypothesized that species-specific bird depredation of TMR can alter the nutritional composition of the ration and that these changes can negatively impact the performance of dairy cows. Blackbirds selected the high energy fraction of the TMR (i.e., flaked corn) and reduced starch, crude fat and total digestible nutrients during controlled feeding experiments. For Holsteins producing 37·1 kg of milk/d, dairy production modeling illustrated that total required net energy intake (NEI) was 35·8 Mcal/d. For the reference TMR unexposed to blackbirds and the blackbird-consumed TMR, NEI supplied was 41·2 and 37·8 Mcal/d, and the resulting energy balance was 5·4 and 2·0 Mcal/d, respectively. Thus, Holsteins fed the reference and blackbird-consumed TMR were estimated to gain one body condition score in 96 and 254 d, and experience daily weight change due to reserves of 1·1 and 0·4 kg/d, respectively. We discuss these results in context of an integrated pest management program for mitigating the depredation caused by pest birds at commercial dairies.
16
Tomiałojć, Ludwik, e Jens Bursell. "Why dark plumage of the European Blackbirds Turdus merula?" Lundiana: International Journal of Biodiversity 7, n. 2 (28 giugno 2007): 127–32. http://dx.doi.org/10.35699/2675-5327.2006.23129.
Testo completoAbstract (sommario):
Why does the European Blackbird’s dark coloration match the ground color of the less widespread of its breeding habitats, the riparian forest, although its main European population occurs in the pale-litter woodland? It is argued that crypsis of all the age stages was more necessary in riparian stands, as this habitat is more risky for the species owing to a high ground vegetation surrounding a foraging bird. Poorer crypsis of Blackbird plumage in pale-litter habitats may be a neutral feature, being compensated by easier scanning of the surroundings over the lower and sparcer herb vegetation and by a tendency to remain in dark sites. The black plumage of the Blackbird male, perhaps reinforced by sexual selection in pristine forest conditions may also retain its cryptic function.
Keywords: Dark/black plumage, crypsis, primeval habitat, European Blackbird Turdus merula.
17
Beletsky, L. David. "Intersexual song answering in Red-winged Blackbirds". Canadian Journal of Zoology 63, n. 3 (1 marzo 1985): 735–37. http://dx.doi.org/10.1139/z85-104.
Testo completoAbstract (sommario):
Female Red-winged Blackbirds (Agelaius phoeniceus) answer their mates' songs with their own songs. Field observations were conducted to determine the extent of song-answering behavior during the Red-winged Blackbird breeding season and to test the hypothesis that song answering in this species is primarily a sexual communication. Females answered significant percentages of their mates' songs during the prenesting and incubation phases of the breeding season, but answering rates declined during the latter phases. Females tended to answer mates when the males were engaged in sexual activities, providing support for the idea that song answering in this species functions in intrapair communication.
18
Heffernan, Michael. "Blackbirds". Iowa Review 17, n. 3 (ottobre 1987): 71–72. http://dx.doi.org/10.17077/0021-065x.3555.
Testo completo
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Clark, Robert G., Patrick J. Weatherhead, Hamilton Greenwood e Rodger D. Titman. "Numerical responses of red-winged blackbird populations to changes in regional land-use patterns". Canadian Journal of Zoology 64, n. 9 (1 settembre 1986): 1944–50. http://dx.doi.org/10.1139/z86-292.
Testo completoAbstract (sommario):
The red-winged blackbird (Agelaius phoeniceus) population in southwestern Quebec more than doubled between 1966 and 1981, apparently in response to increased corn production. In southwestern Ontario less pronounced increases in blackbirds and corn production also occurred. Although larger blackbird populations have been responsible for greater crop damage, it is the waste corn left in fields by mechanical harvesters that supports the increased blackbird population. The increased availability of waste corn during the spring and summer (breeding season) was likely most important in allowing the blackbird population to grow. This conclusion is supported by our census of blackbird populations in 38 counties in southwestern Quebec during the breeding season, which indicated a strong positive correlation between blackbird abundance and corn production in a county. Although corn production explains much variation in the size of blackbird populations, other factors such as the availability of breeding habitat and the spatial distribution of habitats (landscape heterogeneity) may be responsible for additional variation.
20
EDWARDS, SCOTT V., e MEGAN DILLON. "Hitchhiking and recombination in birds: evidence from Mhc-linked and unlinked loci in Red-winged Blackbirds (Agelaius phoeniceus)". Genetical Research 84, n. 3 (dicembre 2004): 175–92. http://dx.doi.org/10.1017/s0016672304007189.
Testo completoAbstract (sommario):
Hitchhiking phenomena and genetic recombination have important consequences for a variety of fields for which birds are model species, yet we know virtually nothing about naturally occurring rates of recombination or the extent of linkage disequilibrium in birds. We took advantage of a previously sequenced cosmid clone from Red-winged Blackbirds (Agelaius phoeniceus) bearing a highly polymorphic Mhc class II gene, Agph-DAB1, to measure the extent of linkage disequilibrium across ~40 kb of genomic DNA and to determine whether non-coding nucleotide diversity was elevated as a result of physical proximity to a target of balancing selection. Application of coalescent theory predicts that the hitchhiking effect is enhanced by the larger effective population size of blackbirds compared with humans, despite the presumably higher rates of recombination in birds. We surveyed sequence polymorphism at three Mhc-linked loci occurring 1·5–40 kb away from Agph-DAB1 and found that nucleotide diversity was indistinguishable from that found at three presumably unlinked, non-coding introns (β-actin intron 2, β-fibrinogen intron 7 and rhodopsin intron 2). Linkage disequilibrium as measured by Lewontin's D' was found only across a few hundred base pairs within any given locus, and was not detectable among any Mhc-linked loci. Estimated rates of the per site recombination rate ρ derived from three different analytical methods suggest that the amounts of recombination in blackbirds are up to two orders of magnitude higher than in humans, a discrepancy that cannot be explained entirely by the higher effective population size of blackbirds relative to humans. In addition, the ratio of the number of estimated recombination events per mutation frequently exceeds 1, as in Drosophila, again much higher than estimates in humans. Although the confidence limits of the blackbird estimates themselves span an order of magnitude, these data suggest that in blackbirds the hitchhiking effect for this region is negligible and may imply that the per site per individual recombination rate is high, resembling those of Drosophila more than those of humans.
21
Bolshakov, C. V., M. D. Evstigneeva e V. N. Bulyuk. "Species-specific attraction call of the blackbird (Turdus merula) in the periods of seasonal migration and breeding". Proceedings of the Zoological Institute RAS 322, n. 2 (25 giugno 2018): 129–43. http://dx.doi.org/10.31610/trudyzin/2018.322.2.129.
Testo completoAbstract (sommario):
We present the results of the analysis of 346 spectrograms of the species-specific attraction call tsiirr issued during daytime and night migration, at migratory stopovers and during breeding by Blackbirds (Turdus merula). The duration of this type signal varies within the range of 102–359 ms, and its frequency is in the intermediate and high frequency range from 5.1 to 9.9 kHz. In the spectrograms most tsiirr signals have one high-frequency and one lower-frequency modulated band. It is assumed that such a structure of this signal allows the birds to maintain contact at a great distance and to determine each other’s spatial position. Temporary and frequency characteristics of the species-specific attraction calls of Blackbirds during nocturnal and daytime migration did not differ significantly. The species-specific attraction calls during the migration flight had on average a much narrower range of sounding than at stopovers. This difference could have been caused by stronger degradation of the signal structure during propagation in migratory flight than at stopovers. The analysis of the spectrograms of the species-specific attraction calls in two pairs of adult Blackbirds during breeding revealed significant individual variation. Signals of migrating individuals at stopovers were shorter and broader than in adult breeding Blackbirds. Our studies of Blackbird acoustic signals, as well as of signals of two other thrush species, Song Thrushes (T. philomelos) and Redwings (T. iliacus), show that during diurnal and nocturnal migratory flights, they use only one type of signal, the speciesspecific attraction call. This call is also used by the birds for communication during migratory stopovers. No specialized migratory signals are given by thrushes during their seasonal movements.
22
Bollinger, Eric K., e James W. Caslick. "Northern corn rootworm beetle densities near a red-winged blackbird roost". Canadian Journal of Zoology 63, n. 3 (1 marzo 1985): 502–5. http://dx.doi.org/10.1139/z85-073.
Testo completoAbstract (sommario):
Population estimates of northern corn rootworm beetles (Diabrotica longicornis (Say), Chrysomelidae; Coleoptera) increased linearly away from a red-winged blackbird (Agelaius phoeniceus (L.), Emberizidae; Passeriformes) roost located at Montezuma National Wildlife Refuge, Cayuga County, New York, U.S.A. Red-winged blackbirds foraging in cornfields near this roost commonly consumed rootworm beetles, indicating that this predation could have been responsible for the lower rootworm beetle populations in this area. However, even if the reduced beetle numbers near the red-winged blackbird roost were the result of predation by this bird, this benefit compensated for only approximately 4% of the damage the birds inflicted to standing corn.
23
Arnold, Todd W. "Variation in laying date, clutch size, egg size, and egg composition of yellow-headed blackbirds (Xanthocephalus xanthocephalus): a supplemental feeding experiment". Canadian Journal of Zoology 70, n. 10 (1 ottobre 1992): 1904–11. http://dx.doi.org/10.1139/z92-259.
Testo completoAbstract (sommario):
I studied the effects of food availability, habitat quality, and timing of breeding on egg production in yellow-headed blackbirds (Xanthocephalus xanthocephalus). Food availability was experimentally manipulated by providing females on six wetlands with supplemental food; six additional wetlands served as unsupplemented controls. Mean nest initiation dates varied by up to 6 d among wetlands, and supplementally fed blackbirds initiated nests 2 d earlier than controls, on average (although this latter difference was not quite significant; P = 0.07). Clutch size declined with laying date, but was unaffected by wetland location, food supplementation, or interactions between these two factors and laying date. Although egg size did not vary among wetlands or in relation to supplemental feeding, egg composition varied with both of these factors. All egg components except wet and dry shell and dry albumen varied among wetlands, whereas total water, wet yolk, and lean yolk were the only components that varied with food supplementation. Large blackbird eggs contained proportionately more water and albumen, but proportionately less yolk and shell. These patterns were somewhat compensatory, such that proportional protein and energy content did not vary with egg size; however, large eggs contained proportionately less fat than did small eggs. Proportional egg composition varied among wetlands (yolk and energy content), but was not affected by supplemental feeding. In general, egg production by yellow-headed blackbirds was not greatly affected by food availability. This may have been due to any of the following four factors: (1) inaccessibility of food supplements owing to competition between male and female blackbirds, (2) insufficient time for females to respond to food supplements, owing to rapid settlement and nest initiation, (3) a nutritionally inappropriate food supplement (i.e., protein availability may not have been enhanced among fed birds), or (4) superabundance of natural foods such that food availability was not limiting egg production.
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Dolbeer, R. A., P. P. Woronecki e J. R. Mason. "Aviary and Field Evaluations of Sweet Corn Resistance to Damage by Blackbirds". Journal of the American Society for Horticultural Science 113, n. 3 (maggio 1988): 460–64. http://dx.doi.org/10.21273/jashs.113.3.460.
Testo completoAbstract (sommario):
Abstract Each of 11 cultivars of sweet corn (Zea mays L.) was presented to red-winged blackbirds (Agelaius phoeniceus L.) in an aviary under no-choice conditions in 1985. This evaluation was repeated in 1986 with eight cultivars, five of which had been tested in 1985. In both years, there were significant differences in damage among cultivars; the damage rankings of the cultivars tested in both years were correlated. Total husk weight and husk weight beyond the cob tip individually explained 68% to 69% of the variation in damage among cultivars. Husk characteristics were more important than kernel characteristics in determining the amount of damage a cultivar received. Six of the cultivars evaluated in a field test near a blackbird roost showed differences in damage similar to that found in the aviary. In the field test, the most- and least-resistant cultivars had 16% and 76% of the ears damaged, respectively. Resistance is a viable approach to reduce damage in situations where sweet corn is grown near concentrations of blackbirds.
25
Castañeda, Xerónimo, Neil Clipperton, Daniel A. Airola, Samantha Arthur e Paul Sousa. "Effectiveness of Public–Private Efforts to Conserve Tricolored Blackbird Colonies on Agricultural Lands in the San Joaquin Valley, California". Western Birds 54, n. 1 (1 febbraio 2023): 2–18. http://dx.doi.org/10.21199/wb54.1.1.
Testo completoAbstract (sommario):
Since the early 1990s when much of the population of the Tricolored Blackbird (Agelaius tricolor) began nesting in fields of triticale grown for dairy silage in the San Joaquin Valley, many colonies have been destroyed inadvertently during harvest. After previous inconsistent efforts, in 2015 a Regional Conservation Partnership Program brought the dairy industry, Natural Resource Conservation Service, Audubon California, California Department of Fish and Wildlife, and other partners together in an effort to stem the losses. The program located colonies and compensated farmers for crop value lost when the harvest was delayed until after the blackbirds fledged and encouraged creation of alternative nesting habitat to attract nesting birds away from agricultural fields. Before 2015, data on the numbers of colonies in silage fields, and on the blackbirds’ productivity conserved and lost, are complete only for 2005–2009, when only 43% of colonies encompassing 60% of the monitored nestings avoided destruction. From 2015 to 2022, 93% of colonies representing 96% of nesting attempts were conserved, and the number of birds nesting in silage increased by as much as 100,000. The program’s success resulted from the adequacy of federal funding, protection provided by the species’ listing as endangered by the state of California, and effective communications and cooperation among the partners and within the dairy industry. Protection of colonies in silage fields since 2015 likely contributed to the substantial increase in the numbers of birds nesting in this habitat and perhaps to an increase in California’s Tricolored Blackbird population as a whole. Continued effort is needed to achieve the species’ recovery.
26
Airola, Daniel A., Tara L. Collins, Christopher J. McColl, Michael R. Lozano, Brett J. Furnas e David E. Krolick. "Foraging Habitat and Its Effects on the Tricolored Blackbird’s Breeding Distribution and Abundance in the Sierra Nevada Foothills, California". Western Birds 54, n. 1 (1 febbraio 2023): 19–31. http://dx.doi.org/10.21199/wb54.1.2.
Testo completoAbstract (sommario):
The grassland-dominated eastern Central Valley and Sierra Nevada foothills of California, from Placer to Stanislaus counties, supported at least 43,000–55,000 breeding Tricolored Blackbirds (Agelaius tricolor) annually from 2014 to 2018—about 30% of the statewide population. We found that within 5 km of a colony, the extent of land cover used for foraging, grassland–herbaceous, and to a lesser extent annual crops and irrigated pasture, exceeded their proportions in this region as a whole, suggesting that nesting Tricolored Blackbirds select colony sites where these habitats are more abundant. Other land-cover types were underutilized for foraging, suggesting avoidance. The probability of Tricolored Blackbird occupancy of blocks of 100 km2 was strongly associated with the extent of the selected land-cover types. The relationship between average density of the breeding population and the extent of the selected land-cover types was significant but weaker, implying that other factors are important in determining density. From 2014 to 2018, development and mining eliminated or degraded 9 of 79 colony sites and made 4 others unsuitable by reducing the extent of nearby foraging habitat, although the total breeding population in the region did not decline. We recommend that conservation measures for the Tricolored Blackbird in federally and state-approved habitat-conservation plans in Placer and Sacramento counties, which support the largest breeding populations in the central Sierra foothills but where urban development is rapid, be reevaluated on the basis of recent colony locations and recognition of the critical role of grassland, annual crops, and irrigated pasture as foraging habitat.
27
Geue, Dirk, e Jesko Partecke. "Reduced parasite infestation in urban Eurasian blackbirds (Turdus merula): a factor favoring urbanization?" Canadian Journal of Zoology 86, n. 12 (dicembre 2008): 1419–25. http://dx.doi.org/10.1139/z08-129.
Testo completoAbstract (sommario):
Humans nowadays dramatically alter environmental and ecological conditions worldwide. One of the most extreme forms of anthropogenic land-use alteration is urbanization. Animals thriving in urban areas are not only exposed to different environmental conditions compared with their nonurban conspecifics, but prevalence and impacts of wildlife diseases on urban populations may also be affected. In the present study, we tested whether blood-parasite prevalence differs between urban and forest habitats by comparing haematozoan infections of urban and forest-living Eurasian blackbirds ( Turdus merula L., 1758). In total, 76% of Eurasian blackbirds were infected with haematozoa and we detected five different blood parasite genera in both habitats. Blood-parasite prevalence varied both between years and between spring and summer in both urban and forest populations. Forest blackbirds had more parasite genera per individual than urban blackbirds, and in summer, forest blackbirds had higher blood-parasite prevalence than their urban conspecifics. These differences in blood-parasite prevalence between urban and forest blackbirds suggest a lower risk of haematozoan infections in urban than in forest habitats. The lower parasite prevalence could be one of the factors favoring the invasion of urban ecosystems.
28
Հայրապետյան, Վ. Տ. "Սև կեռնեխների (Turdus Merula Linnaeus, 1758) բնադրման էկոլոգիան Ստեփանակերտ քաղաքի պայմաններում". Biological Journal of Armenia 74, n. 3 (2022): 58–63. http://dx.doi.org/10.54503/0366-5119-2022.74.3-58.
Testo completoAbstract (sommario):
The ecology of nesting common blackbirds in the territory of Stepanakert city, Artsakh are presented. Although common blackbirds are considered typical forest birds, due to their high ecological flexibility, they easily adapt to urban areas. Through observations, we found out that common blackbirds use about 23 species of plants and artificial structures for nesting in different parts of the city. Nests are built at an average height of 0,5-7 m from the ground, and both natural and anthropogenic materials are used as building materials.
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Ibáñez-Álamo, Juan Diego, Javier Pineda-Pampliega, Robert L. Thomson, José I. Aguirre, Alazne Díez-Fernández, Bruno Faivre, Jordi Figuerola e Simon Verhulst. "Urban blackbirds have shorter telomeres". Biology Letters 14, n. 3 (marzo 2018): 20180083. http://dx.doi.org/10.1098/rsbl.2018.0083.
Testo completoAbstract (sommario):
Urbanization, one of the most extreme human-induced environmental changes, represents a major challenge for many organisms. Anthropogenic habitats can have opposing effects on different fitness components, for example, by decreasing starvation risk but also health status. Assessment of the net fitness effect of anthropogenic habitats is therefore difficult. Telomere length is associated with phenotypic quality and mortality rate in many species, and the rate of telomere shortening is considered an integrative measure of the ‘life stress’ experienced by an individual. This makes telomere length a promising candidate for examining the effects of urbanization on the health status of individuals. We investigated whether telomere length differed between urban and forest-dwelling common blackbirds ( Turdus merula ). Using the terminal restriction fragment assay, we analysed telomere length in yearlings and older adults from five population dyads (urban versus forest) across Europe. In both age classes, urban blackbirds had significantly shorter telomeres (547 bp) than blackbirds in natural habitats, indicating lower health status in urban blackbirds. We propose several potential hypotheses to explain our results. Our findings show that even successful city dwellers such as blackbirds pay a price for living in these anthropogenic habitats.
30
Martin, Pamela A., D. Vaughn Weseloh, Christine A. Bishop, Karin Legierse, Birgit Braune e Ross J. Norstrom. "Organochlorine Contaminants in Avian Wildlife of Severn Sound". Water Quality Research Journal 30, n. 4 (1 novembre 1995): 693–712. http://dx.doi.org/10.2166/wqrj.1995.050.
Testo completoAbstract (sommario):
Abstract Organochlorine contaminants were measured in pooled egg samples of colonial waterbirds, red-winged blackbirds and tree swallows breeding in or near Severn Sound, Lake Huron, an area designated by the International Joint Commission as an Area of Concern, during 1991. Breast muscle samples of staging waterfowl were also collected the preceding autumn. PCBs, DDE and mirex were the most prevalent organochlorine contaminants present in eggs (concentration ranges of 0.065 to 5.452, 0.118 to 3.12 and 0.007 to 0.174 mg/kg, respectively), while oxychlordane, cis-chlordane, dieldrin, heptachlor epoxide, trans-nonachlor, cis-nonachlor, OCS, HCB and beta-HCH were also detectable at low levels in some egg samples. Tetra- and pentachlorobenzene, and alpha-and gamma-HCH were not detected in any of the samples. Generally, the following interspecific gradient in contaminant levels in bird eggs was found: herring gulls = Caspian terns > common terns > tree swallows > blackbirds. Concentrations in the eggs of piscivorous birds in Severn Sound were similar or slightly lower than those from other colonies in Georgian Bay and Lake Huron, and considerably lower than those from colonies in Hamilton Harbour, Lake Ontario. Mirex levels in herring gulls and Caspian terns from Severn Sound colonies were an exception in that they were substantially higher than levels from other Lake Huron colonies (0.174 and 0.167 mg.kg-1 for the two species, respectively, versus <0.12 mg.kg-1), although still much lower than those from Lake Ontario (0.50 and 0.719, respectively). It is probable that mirex was accumulated by gulls and terns during winter or migrational stopovers on Lake Ontario. Low contaminant levels in common terns may have been a result of their consumption of a smaller size class of prey fish. Higher contaminant levels in tree swallow eggs in comparison to red-winged blackbird eggs may have been due to the preponderance of aquatic insects in their diets, as opposed to the larger proportion of terrestrial arthropods in blackbird diets. Only PCBs and DDE were detected in the breast muscle of lesser scaup and mallards.
31
Koglin, Sven, Daronja Trense, Michael Wink, Hedwig Sauer-Gürth e Dieter Thomas Tietze. "Characterization of a de novo assembled transcriptome of the Common Blackbird (Turdus merula)". PeerJ 5 (13 dicembre 2017): e4045. http://dx.doi.org/10.7717/peerj.4045.
Testo completoAbstract (sommario):
Background In recent years, next generation high throughput sequencing technologies have proven to be useful tools for investigations concerning the genomics or transcriptomics also of non-model species. Consequently, ornithologists have adopted these technologies and the respective bioinformatics tools to survey the genomes and transcriptomes of a few avian non-model species. The Common Blackbird is one of the most common bird species living in European cities, which has successfully colonized urban areas and for which no reference genome or transcriptome is publicly available. However, to target questions like genome wide gene expression analysis, a reference genome or transcriptome is needed. Methods Therefore, in this study two Common Blackbirds were sacrificed, their mRNA was isolated and analyzed by RNA-Seq to de novo assemble a transcriptome and characterize it. Illumina reads (125 bp paired-end) and a Velvet/Oases pipeline led to 162,158 transcripts. For the annotation (using Blast+), an unfiltered protein database was used. SNPs were identified using SAMtools and BCFtools. Furthermore, mRNA from three single tissues (brain, heart and liver) of the same two Common Blackbirds were sequenced by Illumina (75 bp single-end reads). The draft transcriptome and the three single tissues were compared by their BLAST hits with the package VennDiagram in R. Results Following the annotation against protein databases, we found evidence for 15,580 genes in the transcriptome (all well characterized hits after annotation). On 18% of the assembled transcripts, 144,742 SNPs were identified which are, consequently, 0.09% of all nucleotides in the assembled transcriptome. In the transcriptome and in the single tissues (brain, heart and liver), 10,182 shared genes were found. Discussion Using a next-generation technology and bioinformatics tools, we made a first step towards the genomic investigation of the Common Blackbird. The de novo assembled transcriptome is usable for downstream analyses such as differential gene expression analysis and SNP identification. This study shows the importance of the approach to sequence single tissues to understand functions of tissues, proteins and the phenotype.
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Dzialowski, Edward M., Tushar S. Sirsat, Sarah K. G. Sirsat e Edwin R. Price. "Breathing while altricial: the ontogeny of ventilatory chemosensitivity in red-winged blackbird (Agelaius phoeniceus) nestlings". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 311, n. 6 (1 dicembre 2016): R1105—R1112. http://dx.doi.org/10.1152/ajpregu.00273.2016.
Testo completoAbstract (sommario):
Altricial bird species, like red-winged blackbirds, hatch at an immature state of functional maturity with limited aerobic capacity and no endothermic capacity. Over the next 10–12 days in the nest, red-winged blackbirds develop increased metabolic capacity before fledging. Although ontogeny of respiration has been described in precocial birds, ontogeny of ventilatory chemosensitivity is unknown in altricial species. Here we examined developmental changes in chemosensitivity of tidal volume (Vt), breathing frequency (ƒ), minute ventilation (V̇e), and whole animal oxygen consumption (V̇o2) from hatching to just before fledging in red-winged blackbirds on days 1, 3, 5, 7, and 9 posthatching (dph) in response to hypercapnia (2 and 4% CO2) and hypoxia (15 and 10% O2). Under control conditions, there was a developmental increase in V̇e with age due to increased Vt. Hypercapnic and hypoxic chemosensitivities were present as early as 1 dph. In response to hypoxia, 1, 3, and 9 dph nestlings increased V̇e at 10% O2, by increasing ƒ with some change in Vt in younger animals. In contrast to early neonatal altricial mammals, the hypoxic response of nestling red-winged blackbirds was not biphasic. In response to hypercapnia, 3 dph nestlings increased V̇e by increasing both ƒ and Vt. From 5 dph on, the hypercapnic increase in V̇e was accounted for by increased Vt and not ƒ. Chemosensitivity to O2 and CO2 matures early in nestling red-winged blackbirds, well before the ability to increase V̇o2 in response to cooling, and thus does not represent a limitation to the development of endothermy.
33
Cholewa, Marta, Łukasz Jankowiak, Magdalena Szenejko, Andrzej Dybus, Przemysław Śmietana e Dariusz Wysocki. "The effects of parental age difference on the offspring sex and fitness of European blackbirds". PeerJ 9 (23 marzo 2021): e10858. http://dx.doi.org/10.7717/peerj.10858.
Testo completoAbstract (sommario):
Background Many studies of birds have indicated that offspring sex ratios can vary with environmental and parental traits. On the basis of long-term research, we first evaluated the possible influence of parental age difference and brood characteristics on offspring sex and fitness in multi-brooded Blackbirds Turdus merula. Methodology The study was conducted in the city-centre Stefan Żeromski Park in Szczecin, NW Poland, where the local population of Blackbirds has been studied since 1996. Data on the offspring sex and fitness were collected in five years, 2005–2007 and 2016–2017. During the breeding season we inspected the study area to locate the pairs’ territories and to track their nests and clutches. Results We found that the overall sex ratio did not differ statistically from 50:50, but that younger females bonded with older mates did tend to produce more sons, probably because of the greater fitness of male descendants. Accordingly, the sons’ breeding success increased with the father’s age, but this relationship was close to non-linear, which may indicate that the transgenerational effect of paternal senescence could negatively affect progeny fitness despite the high-quality of older fathers. Older females mated with younger males produced more daughters, which could have been due to the lesser attractiveness of the males and the mothers’ poorer condition caused by accelerated senescence. We found that neither offspring hatching sequence nor hatching date or clutch sequence were significant for sex determination. Conclusions We consider that in our Blackbird population, parental age could make a more significant contribution to shaping offspring sex and reproductive success.
34
Fletcher, Jr., Robert J., e Rolf R. Koford. "Consequences of rainfall variation for breeding wetland blackbirds". Canadian Journal of Zoology 82, n. 8 (1 agosto 2004): 1316–25. http://dx.doi.org/10.1139/z04-107.
Testo completoAbstract (sommario):
Annual variability in abiotic factors can be pronounced, especially in systems that rely on precipitation, such as arid regions and prairie potholes. We report how annual variation in precipitation from 1999 to 2002 in the Prairie Pothole Region of Iowa, USA, affected both density and reproduction of two interspecific competitors: yellow-headed blackbirds, Xanthocephalus xanthocephalus (Bonaparte, 1826), and red-winged blackbirds, Agelaius phoeniceus (L., 1766). During dry years, yellow-headed blackbirds, an obligate wetland-breeding species, showed a marked reduction in density and a complete reproductive failure in which none of the nests we monitored fledged young. The reproductive failure was attributed primarily to nest predation, which was negatively correlated with water levels in wetlands. Conversely, red-winged blackbirds, a facultative wetland-breeding species, showed little variation in density and nest success. Both species exhibited similar patterns of reduced clutch size and later nest initiation dates in dry years, measures often tied to bottom-up effects of food availability and (or) age of individuals. Yet top-down effects of nest predation had a stronger influence, because lower clutch size did not result in fewer young fledged per successful nest. Incorporating how rainfall variation can affect wetland songbird demography will be critical for understanding population and community dynamics in changing environments.
35
Djemadi, Imed, Badis Bakhouche, Khalil Draidi e Zihad Bouslama. "Biometric data of North African Blackbird Turdus merula: are there many subspecies?" Ornis Hungarica 27, n. 2 (1 dicembre 2019): 67–76. http://dx.doi.org/10.2478/orhu-2019-0016.
Testo completoAbstract (sommario):
Abstract During the past two centuries, few studies have been conducted on biometrics of North African Blackbirds. Several of these studies were carried out during the latter part of the 19th and in the early 20th centuries. As a result, two subspecies were recognized namely Turdus merula algira inhabiting northern regions of North Africa and some localities in southwestern continental Europe and T. m. mauritanicus inhabiting central western Morocco and southern Algeria and Tunisia (to the end of arid climatic regions). In this study we provide morphological data from the northeastern Algerian population of Blackbird. Results reveal no differences between sexes in any of the measurements (small sample size). Comparison of morphological data of specimens collected in the northern region of North Africa and from the southern region of Maghreb countries (Algeria, Tunisia and Morocco) show morphometric differences only in wing length. These results are consistent with the existence of multiple subspecies in North African populations of Blackbird. Our findings support the assumptions of previous researchers in considering T. m. algira as typical of northern areas of Maghreb countries and T. m. mauritanicus typical of southern areas of the region.
36
Lynch, Kathleen S., Matthew I. M. Louder e Mark E. Hauber. "Species-Specific Auditory Forebrain Responses to Non-Learned Vocalizations in Juvenile Blackbirds". Brain, Behavior and Evolution 91, n. 4 (2018): 193–200. http://dx.doi.org/10.1159/000489115.
Testo completoAbstract (sommario):
Species recognition mediates the association of individuals with conspecifics. Learned cues often facilitate species recognition via early social experience with parents and siblings. Yet, in some songbirds, the production of species-typical vocalizations develops in the absence of early social experiences. Here, we investigate the auditory-evoked neural responses of juvenile red-winged blackbirds (Agelaius phoeniceus), a nonparasitic (parental) species within the Icterid family and contrast these results with a closely related Icterid parasitic species that lacks parental care, the brown-headed cowbird (Molothrus ater). We demonstrate that immediate early gene (IEG) activity in the caudomedial mesopallium (CMM) is selectively evoked in response to conspecific non-learned vocalizations in comparison to 2 types of heterospecific non-learned vocalizations, independent of the acoustic similarity patterns between the playback stimuli. This pattern, however, was not detected in the caudomedial nidopallium (NCM). Because the red-winged blackbird is a parental species, the conspecific non-learned vocalization is presumably a familiar sound to the juvenile red-winged blackbird, whereas the heterospecific non-learned vocalizations are novel. We contrast results reported here with our recent demonstration of selective IEG induction in response to non-learned conspecific vocalizations in juvenile parasitic brown-headed cowbirds, in which conspecific non-learned vocalizations are presumably novel. In this case, selective IEG induction from conspecific non-learned vocalization occurred within NCM but not within CMM. By comparing closely related species with stark differences in the early exposure to conspecifics, we demonstrate that CMM and NCM respond to familiar vs. novel non-learned vocalizations in a manner that parallel previously reported regional responses to learned vocalizations such as conspecific songs.
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Linek, Nils, Tamara Volkmer, J. Ryan Shipley, Cornelia W. Twining, Daniel Zúñiga, Martin Wikelski e Jesko Partecke. "A songbird adjusts its heart rate and body temperature in response to season and fluctuating daily conditions". Philosophical Transactions of the Royal Society B: Biological Sciences 376, n. 1830 (14 giugno 2021): 20200213. http://dx.doi.org/10.1098/rstb.2020.0213.
Testo completoAbstract (sommario):
In a seasonal world, organisms are continuously adjusting physiological processes relative to local environmental conditions. Owing to their limited heat and fat storage capacities, small animals, such as songbirds, must rapidly modulate their metabolism in response to weather extremes and changing seasons to ensure survival. As a consequence of previous technical limitations, most of our existing knowledge about how animals respond to changing environmental conditions comes from laboratory studies or field studies over short temporal scales. Here, we expanded beyond previous studies by outfitting 71 free-ranging Eurasian blackbirds ( Turdus merula ) with novel heart rate and body temperature loggers coupled with radio transmitters, and followed individuals in the wild from autumn to spring. Across seasons, blackbirds thermoconformed at night, i.e. their body temperature decreased with decreasing ambient temperature, but not so during daytime. By contrast, during all seasons blackbirds increased their heart rate when ambient temperatures became colder. However, the temperature setpoint at which heart rate was increased differed between seasons and between day and night. In our study, blackbirds showed an overall seasonal reduction in mean heart rate of 108 beats min −1 (21%) as well as a 1.2°C decrease in nighttime body temperature. Episodes of hypometabolism during cold periods likely allow the birds to save energy and, thus, help offset the increased energetic costs during the winter when also confronted with lower resource availability. Our data highlight that, similar to larger non-hibernating mammals and birds, small passerine birds such as Eurasian blackbirds not only adjust their heart rate and body temperature on daily timescales, but also exhibit pronounced seasonal changes in both that are modulated by local environmental conditions such as temperature. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part I)’.
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Tupper, Shelagh K., John L. Cummings e Richard M. Engeman. "Longevity of DayGlo fluorescent particle marker used to mark birds in flight pen and field". Wildlife Research 36, n. 4 (2009): 319. http://dx.doi.org/10.1071/wr09015.
Testo completoAbstract (sommario):
Spray application of fluorescent particles is a widely used and very valuable technique for marking birds. This remains one of the few practical means to mark large numbers of birds for monitoring movement, despite recent availability of a variety of more technologically advanced options. We monitored the longevity of the DayGlo fluorescent particle marker on red-winged blackbirds under simulated field conditions in a flight pen, and in an observational field experiment. In the pen study we banded 52 red-winged blackbirds with individually numbered leg bands, and sprayed them with DayGlo fluorescent particle marker from a distance of ~50 cm, on 1 December 2004. These birds were recaptured and DayGlo fluorescent particle marks assessed 11 times until 10 August 2005. All 31 surviving birds at the conclusion of the study (i.e. after 254 days) retained at least some DayGlo fluorescent particle marker on one or more body regions. Wings retained DayGlo fluorescent particle marks longer than other body regions and thus could be used to identify marks in large-scale collections. Roosting wild blackbirds aerially marked in September and October 2005 retained marks through June 2006, 263 days after marking. The formulation used is inexpensive (US$4.00 L−1), easy-to-apply at many scales and practical for many species (e.g. starlings, blackbirds, sparrows, gulls and shorebirds).
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Wysocki, Dariusz, Łukasz Jankowiak, Marta Cholewa e Dawid Zyskowski. "Natal conditions, lifespan and lifetime reproductive success of European blackbirds". Behavioral Ecology 30, n. 6 (17 agosto 2019): 1707–14. http://dx.doi.org/10.1093/beheco/arz139.
Testo completoAbstract (sommario):
Abstract Even though much has been published in recent years on the factors affecting the lifespan and lifetime reproductive success of birds, there are still gaps in our knowledge. Here, we present the results of a long-term study of European blackbirds which examined the effect of natal conditions on lifespan and lifetime reproductive success (expressed by the number of fledglings) of 152 nestlings (72 males and 80 females) ringed in the Stefan Żeromski Park in Szczecin (NW Poland). We have complete information regarding parental age, family brood (first-egg laying date, clutch size, and hatching sequence), bird size, lifetime reproductive success, pair density and weather conditions during the natal year. For males, total fledgling production was the smaller, the later the laying date of the family brood, but increased with mean daily precipitation and pair density in the natal year. In the case of females, we did not find any significant relationships between their lifetime reproductive success and the above parameters. Male lifespan increased with mean daily precipitation and bird density, but only pair density had a positive effect on female lifespan. We suggest that for females, genetic factors could be more important for their reproductive success than for males. In addition, a blackbird’s lifespan depends strongly on environmental factors.
40
Pribil, Stanislav. "Reproductive success is a misleading indicator of nest-site preferences in the Red-winged Blackbird". Canadian Journal of Zoology 76, n. 12 (1 dicembre 1998): 2227–34. http://dx.doi.org/10.1139/z98-180.
Testo completoAbstract (sommario):
Several methods are used to detect nest-site preferences of birds. One method postulates that individuals will prefer those nest-site features that increase their reproductive success. To determine which features affect reproductive success, and hence should be preferred, the method examines correlations between reproductive success and various nest-site features. When a statistically significant correlation is found, it is concluded that individuals exhibit a preference for that feature. In the absence of a correlation, it is concluded that individuals are indifferent to the feature. Here, I argue that this method may lead to misleading conclusions. If good sites are abundant, all individuals should choose them. Consequently, there will be little variation in the features of the chosen sites. This limited variation, when related to reproductive success, may fail to yield a statistically significant correlation and thus lead to the erroneous conclusion that individuals have no preference. An alternative method of detecting nest-site preferences is to compare features of chosen sites with features of available sites. In this study, I used both methods to investigate nest-site selection in the Red-winged Blackbird (Agelaius phoeniceus). I compared vegetation features of nest sites with those of randomly selected sampling sites and found significant differences. The differences imply that Red-winged Blackbirds prefer vegetation that grows in small patches and is tall and sparse, and the plants have thick stems. I found no relationship between these vegetation features and reproductive success. These results suggest that Red-winged Blackbirds have strong preferences for certain vegetation features, but these preferences cannot be detected from correlations with reproductive success.
41
Parkes, Kenneth C. "ORIOLES, BLACKBIRDS & THEIR KIN". Wilson Bulletin 112, n. 3 (settembre 2000): 439. http://dx.doi.org/10.1676/0043-5643(2000)112[0439:br]2.0.co;2.
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Griffiths, Rachel Eliza. "Watching Blackbirds Turn to Ghosts". Ecotone 3, n. 2 (2008): 22. http://dx.doi.org/10.1353/ect.2008.0062.
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43
Webster, Michael S. "New World Blackbirds: The Icterids". Auk 117, n. 1 (1 gennaio 2000): 270–71. http://dx.doi.org/10.1093/auk/117.1.270.
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Montgomerie, Robert D. "Blackbirds of the Americas.Gordon Orians". Quarterly Review of Biology 61, n. 3 (settembre 1986): 416–17. http://dx.doi.org/10.1086/415087.
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Olson, J. "THE ONTOGENY OF SHIVERING THERMOGENESIS IN THE RED-WINGED BLACKBIRD (AGELAIUS PHOENICEUS)". Journal of Experimental Biology 191, n. 1 (1 giugno 1994): 59–88. http://dx.doi.org/10.1242/jeb.191.1.59.
Testo completoAbstract (sommario):
The ontogeny of shivering thermogenesis was investigated in the altricial red-winged blackbird (Agelaius phoeniceus). Two indices of heat production ­ the rate of oxygen consumption (V(dot)O2) of the bird and the electromyographic (EMG) activity of the pectoralis (PECT) and gastrocnemius (GAST) muscles ­ were measured simultaneously in adult and nestling red-winged blackbirds as they were subjected first to thermoneutral temperatures and subsequently to progressively colder ambient temperatures (Ta). The ontogenetic changes in both indices indicated that the capability for thermogenesis in nestling red-winged blackbirds improved markedly with age. The metabolic rates of 3-day-old nestlings decreased during exposure to gradually falling ambient temperatures; at best, these nestlings were only able to maintain mass-specific V(dot)O2 at levels similar to or slightly above the resting metabolic rate at thermoneutral temperatures (RMR) for a short time before metabolic rates decreased with further cooling. Shivering was detected only in the PECT muscles and was of a relatively low intensity (maximum of sevenfold increase in intensity over basal levels). The 5-day-old nestlings increased mass-specific V(dot)O2 modestly (approximately 1.4-fold) above RMR and attained slightly higher maximal factorial increases in the EMG activity of the PECT (maximum of 18-fold basal levels) when exposed to the same experimental conditions. Shivering was also detected in the GAST muscles of these birds. The most striking improvements in both measures observed during the nestling period occurred between day 5 and day 8. Eight-day-old nestlings increased metabolic rates by approximately 2- to 2.5-fold over basal levels and sustained these elevated rates for longer before becoming hypothermic. Both the PECT and GAST muscles contributed significantly to shivering thermogenesis, and these older nestlings attained much higher factorial increases in the intensity of shivering (up to 72-fold) during exposure to cold temperatures. In addition, both the range and magnitude of the dominant frequencies of muscle activity in the PECT increased during postnatal development. The PECT muscles were a principal site of shivering thermogenesis in all nestling and adult red-winged blackbirds studied here. Shivering in these muscles was a 'first line defense' against cold; the threshold temperature for shivering in the PECT muscles coincided with the lower critical temperature for oxygen consumption (TLC), and the subsequent increases in EMG activity in this muscle with further cooling correlated well with the corresponding increases in mass-specific V(dot)O2.
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Post, Peter, e Frank Götmark. "Foraging Behavior and Predation Risk in Male and Female Eurasian Blackbirds (Turdus Merula) During the Breeding Season". Auk 123, n. 1 (1 gennaio 2006): 162–70. http://dx.doi.org/10.1093/auk/123.1.162.
Testo completoAbstract (sommario):
Abstract In many birds, breeding males display bright colors, sing, and engage in active territory defense; whereas females are less conspicuous. Therefore, it is sometimes assumed that in the breeding season males suffer higher predation than females. Several studies have reported, however, higher female predation rates, which suggests that traits other than coloration and mate-acquisition behaviors are important in determining predation rates for the sexes. Theoretical and empirical work suggests that foraging behavior and foraging rate are major determinants of predation risk. Here, we examine this possibility in a study of breeding Eurasian Blackbirds (Turdus merula) and predation on them by Eurasian Sparrowhawks (Accipiter nisus). Female Eurasian Blackbirds foraged more than males and foraged closer to the ground, both early and late in the breeding season. On the basis of this observation, we predicted that females should suffer higher predation than males. Of 98 Eurasian Blackbirds taken in 33 Eurasian Sparrowhawk territories during four years, 56 were females and 42 males. On the basis of the male-biased sex ratio in the population, female Eurasian Blackbirds suffered higher predation risk than males. For breeding birds, these results indicate a trade-off between foraging effort and predation rate, which is of importance for sexual dichromatism (selection for female crypsis), population sex ratio, and behaviors of the sexes. Le Comportement de Quête Alimentaire et les Risques de Prédation chez Turdus merula au Cours de la Saison de Reproduction
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Twedt, Daniel J., William J. Bleier e George M. Linz. "Genetic variation in male Yellow-headed Blackbirds from the northern Great Plains". Canadian Journal of Zoology 70, n. 11 (1 novembre 1992): 2280–82. http://dx.doi.org/10.1139/z92-305.
Testo completoAbstract (sommario):
Electrophoretic differences at 15 presumptive loci were used to assess allelic frequencies, heterozygosities, and polymorphism for male Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) collected in east-central Alberta, north-central North Dakota, and east-central South Dakota. Five loci were polymorphic and mean heterozygosities ranged from 0.119 to 0.133. Significant differences were detected among these geographic populations of Yellow-headed Blackbirds, primarily due to differences in the allelic frequencies of isocitrate dehydrogenase and glucose-6-phosphate dehydrogenase. Differences detected were not sufficient to uniquely identify the geographic origin of Yellow-headed Blackbrids.
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Nemeth, Erwin, Nadia Pieretti, Sue Anne Zollinger, Nicole Geberzahn, Jesko Partecke, Ana Catarina Miranda e Henrik Brumm. "Bird song and anthropogenic noise: vocal constraints may explain why birds sing higher-frequency songs in cities". Proceedings of the Royal Society B: Biological Sciences 280, n. 1754 (7 marzo 2013): 20122798. http://dx.doi.org/10.1098/rspb.2012.2798.
Testo completoAbstract (sommario):
When animals live in cities, they have to adjust their behaviour and life histories to novel environments. Noise pollution puts a severe constraint on vocal communication by interfering with the detection of acoustic signals. Recent studies show that city birds sing higher-frequency songs than their conspecifics in non-urban habitats. This has been interpreted as an adaptation to counteract masking by traffic noise. However, this notion is debated, for the observed frequency shifts seem to be less efficient at mitigating noise than singing louder, and it has been suggested that city birds might use particularly high-frequency song elements because they can be produced at higher amplitudes. Here, we present the first phonetogram for a songbird, which shows that frequency and amplitude are strongly positively correlated in the common blackbird ( Turdus merula ), a successful urban colonizer. Moreover, city blackbirds preferentially sang higher-frequency elements that can be produced at higher intensities and, at the same time, happen to be less masked in low-frequency traffic noise.
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Dybus, Andrzej, Anna Siemierz, Dariusz Wysocki, Iwona Szatkowska, Magdalena Muszyńska e Sebastian Guenzel. "Evaluation of the applicability of polymerase chain reaction (PCR) to sex identification in Eurasian blackbirds (Turdus merula)". Biological Letters 46, n. 1 (1 gennaio 2009): 15–20. http://dx.doi.org/10.2478/v10120-009-0009-x.
Testo completoAbstract (sommario):
Evaluation of the applicability of polymerase chain reaction (PCR) to sex identification in Eurasian blackbirds (Turdus merula)Turdus merulais one of most common bird species in Europe. This study verified a method for its sex identification by PCR with P2/P8 primers, based on theCHD1gene polymorphism, proposed in earlier studies as a universal tool for sex identification in most bird species. Although there are some reports that PCR cannot determine sex in Eurasian blackbirds due to a lack of differences in intron lengths ofCHD1-ZandCHD1-Wgenes, our study showed that such a possibility does exist, so it can contribute to an increased understanding of the biology of this species.
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de Queiroz, Alan. "Double-scratching by Yellow-headed Blackbirds". Wilson Journal of Ornithology 120, n. 3 (settembre 2008): 657–59. http://dx.doi.org/10.1676/07-090.1.
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