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1
Dalla, Rosa Luciano. "Modeling the foraging habitat of humpback whales". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/23486.
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Knowing how species will respond to environmental variability and climate change requires understanding the factors that influence their distribution and movement patterns. I investigated the processes that drive individuals to concentrate in specific areas of their home range by modeling encounter rates of humpback whales (Megaptera novaeangliae) in relation to environmental variables using GIS tools, generalized additive models, and remote sensing and in situ data. I conducted this work at two foraging areas: the coastal waters of British Columbia, Canada, and the Bransfield and Gerlache Straits, Antarctica.
Humpback whales in British Columbia were strongly associated with latitude and bathymetric features. The relationships with remotely sensed variables reflecting primary productivity were not consistent, but higher numbers of whales seemed to be associated with higher productivity. In fact, the highest concentrations of humpback whales appeared to reflect areas where concentration and retention processes lead to higher biological productivity, including south Dixon Entrance, middle and southwestern Hecate Strait and off Juan de Fuca Strait.
Humpback whales in the Southern Ocean also preferred areas of enhanced biological productivity. In Gerlache Strait, humpback whales were associated with areas of higher chlorophyll-a concentration in the central and northern sections of the strait, which also corresponded to relatively higher temperatures and shallower mixed layer depths for the in situ data. In Bransfield Strait, humpback whales appeared to prefer the near-frontal zones and the deep basins, where surface waters are influenced by the Bransfield Current. Interannual variability in both humpback and minke whale encounter rates in Gerlache Strait was correlated with the Oceanic Niño Index, the oceanic component of ENSO.
In addition to investigating species-habitat relationships with statistical models, I conducted the first study to describe the satellite-monitored movements of humpback whales on their feeding grounds along the Antarctic Peninsula. Results showed considerable individual variation in direction, speed and range of movements, and an overall pattern characterized by short- and long-distance movements between presumed foraging areas with relatively short residency times.
All told, the results of my research show that humpback whale distribution within foraging habitat is influenced by physical and biological variables that enhance biological productivity.
2
Gilbert, Andrew. "The Foraging and Habitat Ecology of Black Terns in Maine". Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/GilbertAT2001.pdf.
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Convery, Ken M. "Assessing Habitat Quality for the Endangered Red-cockaded Woodpcker". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/10136.
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This project had 2 major objectives. The first objective was to assess how well the revised U.S. Fish and Wildlife Service Foraging Habitat Guidelines depict good quality habitat for the red-cockaded woodpecker (Picoides borealis) at Camp Lejeune, NC. To accomplish this, I used multiple linear and logistic regression to examine the relationships between fitness, habitat use, home range size, and habitat characteristics described in the guidelines. I assumed that habitat characteristics that confer quality were related to higher fitness, greater habitat use, and reduced home range size. To a large extent, the guidelines are validated. Red-cockaded woodpeckers responded favorably to habitat that mimics the historical, mature, and fire-maintained pine forests of the southeastern U.S., characterized by high densities of large pines, low densities of small and medium pines, and a lush herbaceous groundcover. Variables positively associated with habitat use and fitness were associated with reduced home range size, and those negatively associated with habitat use and fitness with increased home range size. Percent herbaceous groundcover was a significant regressor indicative of quality in every model. The second objective was to assess how well USFWS foraging partitions represent habitat used by red-cockaded woodpeckers. I conducted home range follows of 23 groups of red-cockaded woodpeckers and estimated the percentage of each home range encompassed by partitions of varying radii. The percentage of the actual home range included in the partition increased as a function of partition radius. The standard 800 m circular partition, on average, included 91% of the home range, but significant variation existed between groups.Master of Science
4
Convery, Ken. "Assessing Habitat Quality for the Endangered Red-cockaded Woodpcker". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/10136.
Pełny tekst źródłaStreszczenie:
This project had 2 major objectives. The first objective was to assess how well the revised U.S. Fish and Wildlife Service Foraging Habitat Guidelines depict good quality habitat for the red-cockaded woodpecker (Picoides borealis) at Camp Lejeune, NC. To accomplish this, I used multiple linear and logistic regression to examine the relationships between fitness, habitat use, home range size, and habitat characteristics described in the guidelines. I assumed that habitat characteristics that confer quality were related to higher fitness, greater habitat use, and reduced home range size. To a large extent, the guidelines are validated. Red-cockaded woodpeckers responded favorably to habitat that mimics the historical, mature, and fire-maintained pine forests of the southeastern U.S., characterized by high densities of large pines, low densities of small and medium pines, and a lush herbaceous groundcover. Variables positively associated with habitat use and fitness were associated with reduced home range size, and those negatively associated with habitat use and fitness with increased home range size. Percent herbaceous groundcover was a significant regressor indicative of quality in every model. The second objective was to assess how well USFWS foraging partitions represent habitat used by red-cockaded woodpeckers. I conducted home range follows of 23 groups of red-cockaded woodpeckers and estimated the percentage of each home range encompassed by partitions of varying radii. The percentage of the actual home range included in the partition increased as a function of partition radius. The standard 800 m circular partition, on average, included 91% of the home range, but significant variation existed between groups.Master of Science
5
Walsh, Allyson Louise. "Foraging habitat, weather and the conservation of bats in Britain". Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294573.
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Nelson, Josiah. "Habitat Use and Foraging Ecology of Bats in North Dakota". Diss., North Dakota State University, 2016. http://hdl.handle.net/10365/25849.
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Habitat use is a key component to understanding the conservation needs of species. While an array of quantitative analyses for studying fine-scale habitat use and selection have been developed, such methods have rarely been applied to bat species, with most work focused at a broad scale or using qualitative methods. Insectivorous bat communities face major threats from habitat conversion, exploitation of natural resources, and the impending spread of white-nose syndrome. Hence, detailed knowledge of their habitat needs is critical for developing effective management plans. In North Dakota, little was known about local bat populations prior to 2009, with essentially no knowledge of habitat associations and preferences of bat species. The overall objective of this research was to survey habitats across North Dakota to document species occurrences within key ecological regions and to assess the influence of fine-scale habitat characteristics on community diversity and foraging patterns. We further aimed to assess the foraging habitat selection of little brown bats, Myotis lucifugus, a species of conservation concern. Our specific objectives were to: 1) assess species? occurrence and distributions within North Dakota; 2) assess the influence of habitat and the availability of water resources on species diversity and community-level foraging activity; 3) identify habitats associated with areas of high foraging activity; 4) identify indicator species that characterize key habitats; 5) assess foraging habitat selection of female M. lucifugus; 6) and assess individual variation in habitat selection of M. lucifugus. From 2009 to 2012, mist netting and acoustic surveys were conducted to document species occurrence at 68 sites. From 2012 to 2015, targeted acoustic surveys were conducted at 37 sites to assess foraging activity levels in variable habitats. In 2014 and 2015, data-logging telemetry receivers were used to assess foraging habitat selection of M. lucifugus. The presence of 11 species was confirmed in the state. We found that bat community diversity and foraging activity were influenced by fine-scale habitat characteristics. M. lucifugus selected for edge habitats and nearby water sources. These results will be valuable for the conservation and management of bats and provide baseline information for future research on habitat use of bats.North Dakota Game and Fish Department
7
Berkelman, James. "Habitat Requirements and Foraging Ecology of the Madagascar Fish-Eagle". Diss., Connect to this title online, 1997. http://scholar.lib.vt.edu/theses/available/etd-5852152749721461/.
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Hall, Anna Marie. "Foraging behaviour and reproductive season habitat selection of northeast pacific porpoises". Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/37218.
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Behavioural observations are fundamental to understanding and defining the habitat needs of animals. I compiled the behavioural repertoires reported for harbour (Phocoena phocoena) and Dall’s porpoise (Phocoenoides dalli) by classifying the life processes of phocoenids into 12 descriptive categories. This range-wide review revealed complex sexual and social behaviours, similar foraging behaviours and breeding site fidelity, as well as differences in habitat selection between these two northern hemisphere species. I also conducted a fine-scale field study of harbour porpoise foraging behaviour at two sites in Juan de Fuca Strait (British Columbia) using point transect survey data (2007–2008), and platforms of opportunity data (1995–1996, 1998–2008) to determine the physical conditions under which harbour porpoise foraged and the extent to which they displayed specialised behaviours. I examined harbour porpoise presence, density and group sizes relative to tidal currents, tidal variation, lunar phase, lunar position, solar position, diurnality, seasonality and presence of conspecifics—and found that greater numbers of harbour porpoise occurred on the ebb current during the spring tides. Numbers of porpoise increased three-fold between April and October, when calves and high-energy behaviours were also more prevalent. To identify porpoise breeding habitat in the inland waters of southern British Columbia and northwestern Washington, I used systematically and opportunistically collected sightings of harbour and Dall’s porpoise (1991–2008), and compared group sizes and frequency of occurrences for both species relative to bathymetry and tidal speeds. Overall, I found that both species selected bathymetrically differentiated habitats that were characterized by high rates of tidal mixing (with harbour porpoise preferring regions ≤100 m, and Dall’s porpoise preferring 151 – 250 m). Spatial analysis identified two separate areas that may be species-specific breeding habitats—the first to be identified for either species in this region. In summary, harbour porpoise maintained stable group sizes and used tidally well-mixed foraging sites on a temporary but predictable basis. Dall’s porpoise were associated with these same areas, but habitat partitioning associated with differences in bathymetry occurred in important breeding areas that may account for the coastal parapatric distribution of these two high trophic level predators.
9
Vaughan, Nancy. "Partitioning of foraging habitat resources among bats (Chiroptera) in Great Britain". Thesis, University of Bristol, 1996. http://hdl.handle.net/1983/5dae8611-bacc-4ff5-a3dc-49f7e3d1131f.
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Ribeiro, Emanuel Ferreira. "Seasonal variation in foraging habitat preferences in Lesser Kestrel Falco naumanni". Master's thesis, Universidade de Aveiro, 2007. http://hdl.handle.net/10773/720.
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Conhecer as preferências de habitat de uma espécie é crucial para a
definição e implementação de medidas com objectivos de conservação.
Neste estudo analisamos a preferência de habitat de caça de uma espécie
ameaçada, e a maneira como estas preferências se alteram ao longo da
época de reprodução. A disponibilidade de cada tipo de habitat varia
consoante as actividades agrícolas, como sementeiras, aragem ou ceifas.
Os resultados evidenciam que esta espécie selecciona diferentes tipos de
habitat de acordo em cada fase do ciclo reprodutor. No início da época
de reprodução, a espécie, prefere caçar em terrenos arados enquanto que
no final prefere campos de cereais já ceifados nesta fase, e onde apenas
há restolhos. As diferenças observadas não seriam detectadas caso não se
considerassem as alterações de habitat inerentes às actividades agrícolas.
Os Francelhos preferem caçar em habitats com vegetação baixa e pouco
densa provavelmente devido à maior disponibilidade de presas neste tipo
de habitats. Machos e fêmeas não apresentam diferenças significativas
em parâmetros de caça como a taxa de êxito ou o tempo de caça
necessário para capturar uma presa. A taxa de êxito foi mais elevada em
restolhos e no período incubação e mais baixa em terrenos arados e
durante o período de pré-incubação. As aves despendem menos tempo
para efectuar um primeiro ataque em cereal e do que em plantações de
algodão.
Em plantações de cereais é necessário menos tempo para capturar uma
presa enquanto que nos algodoais é necessário um maior esforço de caça.
O número de ataques por minuto de observação não é significativamente
diferente entre biótopos.Knowing the habitat preference of a species is of crucial importance in order to sketch measures with conservational purposes. In this study we analyse the foraging habitat preferences of a threatened species and how they change through the breeding season. Habitat availability varies due to changes in agricultural activities such as ploughing, sowing, or harvesting. Our results evidence that this species select different habitat types according to breeding season stage. In the beginning of the season prefer to forage in ploughed fields while during chick rearing and post-fledging prefer cotton fields and cereal stubbles. Thus changes in agricultural activities must be considered in habitat selection studies. Lesser kestrels prefer to forage in low height and sparse cover, probably because of higher prey availability in this kind of habitats. Males and females don’t show significant differences in several hunting parameters. Success rate was higher in cereal stubble and during incubation and lower in ploughed fields and in the pre-incubation period. Lesser kestrels take less time to make a strike in cereal stubble and more in cotton plantations. In cereals prey capture takes less time while in cotton takes more hunting effort. The number of strikes per minute of observation didn’t varied significantly between habitats.
11
Fussman, Jennifer Lynn. "Foraging ecology of Kirtland's Warblers in managed and natural breeding habitat". Connect to resource, 1997. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1260989687.
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Manco, Fabrizio. "Chinstrap penguin (Pygoscelis antarcticus) foraging habitat model for the South Orkney Islands". Thesis, Anglia Ruskin University, 2017. http://arro.anglia.ac.uk/703809/.
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The Southern Ocean is under several threats due to global human activities but also to local resource exploitation. The chinstrap penguin (Pygoscelis antarcticus) is a key species in the Antarctica marine food web. Along with other predators, it has been impacted, albeit mostly indirectly, by harvesting in the past. The recent overlap and competition with krill fisheries necessitates constant attention and a better understanding of how this species utilises its environment; this can be achieved partly by developing a model of their foraging habitat. In this context, birds from two different colonies in the South Orkney Islands have been tracked with GPS devices and TDR loggers during the breeding season. The resulting dataset allowed me to create a three dimensional representation of their foraging trips. The different methodological approaches I designed allowed me to assess how the birds use their environment across space and time. By studying changes in movements, I was able to detect when the birds were foraging. Linking these foraging locations with explanatory environmental variables, I was then able to develop a foraging habitat model for this species around the South Orkney Islands. The model went through a series of performance measurements and validation processes. The final resulting map offers a picture of where chinstrap penguins forage from their colonies. The range of foraging, the density of birds, the hotspot areas, the depths of foraging and how these parameters change with time can be used to support policies and management targets. I believe these results can also be useful for further studies.
13
Manco, Fabrizio. "Chinstrap penguin (Pygoscelis Antarcticus) foraging habitat model for the South Orkney Islands". Thesis, Anglia Ruskin University, 2017. https://arro.anglia.ac.uk/id/eprint/703809/1/Manco_2017.pdf.
Pełny tekst źródłaStreszczenie:
The Southern Ocean is under several threats due to global human activities but also to
local resource exploitation. The chinstrap penguin (Pygoscelis antarcticus) is a key
species in the Antarctica marine food web. Along with other predators, it has been
impacted, albeit mostly indirectly, by harvesting in the past. The recent overlap and
competition with krill fisheries necessitates constant attention and a better
understanding of how this species utilises its environment; this can be achieved partly
by developing a model of their foraging habitat.
In this context, birds from two different colonies in the South Orkney Islands have been
tracked with GPS devices and TDR loggers during the breeding season. The resulting
dataset allowed me to create a three dimensional representation of their foraging trips.
The different methodological approaches I designed allowed me to assess how the birds
use their environment across space and time. By studying changes in movements, I was
able to detect when the birds were foraging. Linking these foraging locations with
explanatory environmental variables, I was then able to develop a foraging habitat
model for this species around the South Orkney Islands.
The model went through a series of performance measurements and validation
processes. The final resulting map offers a picture of where chinstrap penguins forage
from their colonies. The range of foraging, the density of birds, the hotspot areas, the
depths of foraging and how these parameters change with time can be used to support
policies and management targets. I believe these results can also be useful for further
studies.
14
Griffin, Larry Roy. "The distribution and abundance of the rook Corvus frugilegus L. as influenced by habitat suitability and competitive interactions". Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4640/.
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Rooks (Corvus frugilegus) are colonially breeding corvids found in most agricultural landscapes. Colonies in the County Durham area tend to be clustered at distances up to 500 m, but otherwise show little pattern in terms of spacing or size. Colony size was comparable between sites as changes in colony nest counts were allowed to stabilise before the whole area was surveyed. When measuring nest build-up at a sample of colonies in 1996, no further significant increases occurred after 9th April. The spatial size distribution of colonies was maintained between years. The distribution and size of breeding colonies is modelled in relation to the interaction between the spatial distribution of the foraging habitat and potential intraspecific competitors, with the identification of the distance over which this interaction is strongest. The satellite derived habitat data used for the modelling were part of the ITE Land Cover Map of Great Britain. However, their correspondence with ground reference data was found to be severely lacking. Thus, for modelling the availability of nesting habitat, OS woodland data were used as these identified more of the extant rookery sites, whilst the ITE data were retained for quantifying the foraging habitat. Logistic regression showed that the distribution of colony sites was influenced by the availability of woodland blocks large enough to hold a colony, proximity to roads and buildings, and by the amount of pasture within 1 km. Other suitable sites with these characteristics remained unoccupied within the distribution. Partial Correlations showed that interactions between the spatial distribution of the foraging habitat and competitors influenced colony size at distances up to 6 km, suggesting their effect outside of the breeding season. The multiple regression model built with variable values for this distance explained 31% of the variance in colony size. When applied to the potential breeding sites identified using the logistic regression, most sites still remained suitable. This suggests the distribution is not saturated and that limited availability of breeding habitat is not the cause of the nesting aggregations. The broad correlation of Rook abundance to foraging habitat and potential competitors corresponds to an ideal free distribution of individuals across colony sites. This is supported by models of Rook numbers in relation to parish agricultural statistics produced by MAFF. These again show the importance of pasture as a probable foraging resource, and how pasture quality could be important to Rook numbers. The models also supported the ideal free predictions of spatial variation in Rook abundance in relation to habitat, and the response of colony sizes to temporal change in habitat quality.
15
Zavalaga, Carlos B. "Foraging behavior of Peruvian boobies Sula variegata in northern Peru an analysis of intersexual foraging segregation and marine habitat use /". View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3/r1/zavalagac/carloszavalaga.pdf.
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Thesis (Ph.D.)--University of North Carolina Wilmington, 2008Title from PDF title page (viewed May 26, 2009) Includes bibliograpical references (p. 80-83) Includes bibliographical references (p. 80-83)
16
Stolen, Eric Douglas. "Habitat selection and foraging success of wading birds in impounded wetlands in Florida". [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013802.
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Atkinson, Robert Peter Douglas. "The ecology of the side-striped jackal (Canis adustus Sundevall), a vector of rabies in Zimbabwe". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389001.
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Rowcliffe, J. Marcus. "The population ecology of brent geese and their food plants". Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365866.
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Bakaloudis, Dimitris E. "The ecology of short-toed eagle (Circaetus gallicus, GM.) in dadia-lefkimi-soufli forest complex, Thrace, Greece". Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325211.
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Milbern, Lana Cecile. "Habitat usage of breeding songbirds in urban Columbus, Ohio". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587476090513815.
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Kale, Atul. "Evaluation of red-cockaded woodpecker habitat using a red-cockaded woodpecker foraging matrix application". Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219848445/.
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Shi, Jianbin. "Habitat selection and foraging ecology of feral goats on the Isle of Rum, Scotland". Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250289.
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Davidson-Watts, Ian. "Roost selection, foraging behaviour and habitat use by two cryptic species of pipistrelle bat". Thesis, Open University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437798.
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Pearl, Benjamin G. "Factors affecting Western Snowy Plover winter foraging habitat selection in San Francisco Bay ponds". Thesis, San Jose State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10011661.
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Within the San Francisco Bay Area, Western Snowy Plovers (Alexandrinus nivosus nivosus) nest and winter in former salt ponds. They face a number of threats including human-altered habitats and high levels of predation by mesopredators and raptors. The South Bay Salt Pond Restoration Project (the Project) is a large wetland restoration project that will change and potentially eliminate Snowy Plover habitat in the region. As the Project returns salt ponds to tidal wetland, there will be less of the dry, flat, and sparsely vegetated habitat that plovers need for breeding and wintering habitat. A greater understanding of the specific microhabitat requirements for high quality plover foraging sites is needed. In particular, it is important for managers to understand what constitutes high quality wintering habitat for Snowy Plover numbers. This study assessed the characteristics at sites where Snowy Plovers winter in former salt ponds, especially habitat traits related to promoting plover foraging. Analysis of plover foraging habitat showed that plovers were associated with increasing plant height, water cover, and distance from perches and levees. This information is designed to inform restoration and management decisions in efforts to meet Snowy Plover recovery goals in the South San Francisco Bay.
25
Vaudo, Jeremy. "Habitat Use and Foraging Ecology of a Batoid Community in Shark Bay, Western Australia". FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/367.
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Worldwide declines in populations of large elasmobranchs and the potential cascading effects on marine ecosystems have garnered considerable attention. Far less appreciated are the potential ecological impacts of changes in abundances of small to medium bodied elasmobranchs mesopredators. Crucial to elucidating the role of these elasmobranchs is an understanding of their habitat use and foraging ecology in pristine conditions. I investigated the trophic interactions and factors driving spatiotemporal variation in abundances of elasmobranch mesopredators in the relatively pristine ecosystem of Shark Bay, Australia. First, I describe the species composition and seasonal habitat use patterns of elasmobranch mesopredator on the sandflats of Shark Bay. Juvenile batoids dominated this diverse community and were extremely abundant in nearshore microhabitats during the warm season. Stomach content analysis and stable isotopic analysis revealed that there is a large degree of dietary overlap between common batoid species. Crustaceans, which tend to be found in seagrass habitats, dominated diets. Despite isotopic differences between many species, overlap in isotopic niche space was high and there was some degree of individual specialization. I then, investigated the importance of abiotic (temperature and water depth) and biotic (prey and predator abundance) factors in shaping batoid habitat use. Batoids were most abundant and tended to rest in shallow nearshore waters when temperatures were high. This pattern coincides with periods of large shark abundance suggesting batoids were seeking refuge from predators rather than selecting optimal temperatures. Finally, I used acoustic telemetry to examine batoid residency and diel use of the sandflats. Individual batoids were present on the sandflats during both the warm and cold seasons and throughout the diel cycle, suggesting lower sandflat densities during the cold season were a result of habitat shifts rather than migration out of Shark Bay. Combined, habitat use and dietary results suggest that batoids have the potential to seasonally impact sandflat dynamics through their presence, although foraging may be limited on the sandflats. Interestingly, my results suggest that elasmobranch mesopredators in pristine ecosystems probably are not regulated by food supply and their habitat use patterns and perhaps ecosystem impacts may be influenced by their predators.
26
Reynolds, Michelle H. "The Foraging Ecology, Habitat Use, and Population Dynamics of the Laysan teal (Anas laysanensis)". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/29649.
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The Laysan teal, an endangered species, is restricted to a single population on Laysan Island, a remote atoll of the Hawaiian archipelago. Little is known of the Laysan teal's ecology, therefore, I examined food habits, habitat use, and population dynamics. These aspects of its ecology are fundamental to the species management and conservation. I described diel and nocturnal habitat use, home range, and foraging with radio telemetry in 1998-2000. Most individuals showed strong site fidelity during the tracking period, but habitat selection varied between individuals. Mean home range size was 9.78 ha (SE 2.6) using the fixed kernel estimator (95% kernel; 15 birds with >25 locations). Foraging was strongly influenced by time of day: birds spent only 4% of their time foraging in the day, but spent 45% of their time foraging at night. Time activity budgets from the island's four habitat zones indicated that the coastal zone was rarely used for foraging. The birds foraged 42% of the time they spent in the terrestrial zone at night, but foraged only 4-6% of the time they spent there during other times. Fecal analysis and behavioral observations revealed that the Laysan teal is not a 100% macro-insectivore as previously reported, but consumed seeds, succulent leaves, and algae, in addition to adult diptera, diptera larvae and pupae, ants, seeds, lepidoptera, coleoptera, and Artemia. I concluded that this species exhibits high plasiticity in foraging behavior. Laysan teal appear to opportunistically select abundant, high energy prey for the breeding season, due to constrained resources on Laysan Island.
I also studied the parameters influencing the Laysan teal's population dynamics. Adult survival is high, but duckling survival on Laysan is low, and is a primary demographic parameter limiting population growth. Estimates indicate the population density was high (between 546-827) from 1991 until August 1993, prior to a population crash that occurred between September and December 1993. The most current population estimate (Sept-Nov 2001) is 444 (SE 181) adults. Additional populations (translocation), along with control of non-native mammalian predators, are needed to reduce extinction risks to the Laysan teal.Ph. D.
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Williams-Sieg, Kelly A. "Avian Community Composition and Foraging Behavior in Response to Commercial Thinning and Habitat Structure". Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1212765381.
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Bloxton, Thomas David. "Prey abundance, space use, demography, and foraging habitat of northern goshawks in western Washington /". Thesis, PURL, 2002. http://www.arlis.org/docs/vol1/A/52084482.pdf.
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Finn, Paul. "Habitat selection, foraging ecology and conservation of Eastern Curlews on their non-breeding grounds". Thesis, Griffith University, 2010. http://hdl.handle.net/10072/365306.
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Migratory shorebirds generally utilise very different habitats, great distances apart, during breeding and non-breeding seasons. The coastal intertidal flats in their non-breeding range provide a wide variety of benthic prey and shorebirds are primarily utilising these habitats for there foraging potential. Feeding strategies among shorebirds are largely determined by morphology and broadly range from visual pecking at the substrate surface to tactile probing deep within the sediment. Some shorebirds are capable of very deep (>15 cm) and complex probing of the sediment and this feeding guild is represented globally by three very large curlew species: Eastern Curlews (Numenius madagascariensis), Eurasian Curlews (N. arquata) and Long-billed Curlews (N. americanus). These deep-probing shorebirds are threatened globally due to recent declines in population sizes, largely resulting from habitat loss and hunting pressure. To prevent further loss and possible extinction of shorebirds at risk, better knowledge of their feeding ecology outside the breeding grounds is required. Moreton Bay on Australia’s subtropical east coast supports over 15% of the global population of Eastern Curlews during the austral summer months and is therefore of worldwide importance for this species during its non-breeding season. The present study investigates the feeding ecology of the Eastern Curlew in Moreton Bay and what drives their habitat choice on these nonbreeding grounds.
Initially the broadscale distribution of Eastern Curlews among tidal flats within Moreton Bay was assessed. Low-tide surveys were conducted with the help of 60 skilled volunteers who made repeated counts at defined sections of tidal flat (sites) totalling approximately 41.3% (9,500 ha) of the intertidal habitat within Moreton Bay. Sites varied in size (0.68–474 ha), substrate, topography, and other features. There was a very high consistency between counts on different days within a month and different months within a season, across all sites. Winter numbers of Eastern Curlews totalled about 25% of those in summer, and the proportional distribution of birds among sites was generally similar across both seasons. The within-season constancy of curlew numbers across sites suggests that short surveys can give reliable results. Curlew densities (birds/ha) also showed a strong correlation between summer and winter counts. Curlew density varied greatly among tidal flats and important intertidal feeding habitat was identified.
Numbers of Eastern Curlews on low-tide feeding grounds were then compared with those at high-tide roosts in order to understand their habitat use more fully. Counting shorebirds on feeding grounds provided an accurate population census tool but a relatively large area had to be covered compared with counting birds at roost sites. The correspondence between numbers of curlews at high-tide roosts was compared with those on low-tide feeding grounds at several spatial scales, leading to the conclusion that the typical distance birds travelled between roosts and feeding grounds would be in the order of 5–10 km, with high mobility between alternative roosts and/or feeding grounds occurring at or below this distance.
The habitat preferences of curlews were next investigated at large (betweenflat) and small (within-flat) spatial scales in order to determine factors underlying habitat selection. Using data from the low-tide surveys of feeding grounds, 32 defined sections of intertidal flat (sites; 200–400 ha in area) which varied greatly in their curlew density and other environmental characteristics were analysed. Of ten environmental characteristics measured for each site, substrate resistance was the best predictor of curlew density at the broad scale. Sites with the least resistant substrates had curlew densities three times those with the most resistant substrates. Characteristics that were poor predictors included distance to the nearest roost, level of human disturbance and intertidal area and width. For a finer-scale assessment, microhabitat use and feeding behaviour were recorded during low tide within 12
intertidal flats, which varied in size (23–97 ha), curlew density, substrate and other features. Across all flats, curlews strongly preferred to feed relatively close (0–50 m) to the moving low water line. They fed on a variety of substrates (including sand, sandy-mud, mud and seagrass) in broadly similar proportions to their occurrence in the habitat. There was a statistically significant preference for sand, although its magnitude was not strong. These results indicated that curlews selected habitat more strongly at the between-flat rather than the within-flat scale.
The curlews' diet was next quantified across the same 12 intertidal flats described above, though 970 focal observations (each of 3 minutes duration). Food resources were also estimated from substrate core samples. Curlew density, estimated at each site using low-tide surveys from every site visit, showed a strong positive association with both the density and biomass of prey across the 12 flats. However, the density and biomass of prey also showed a strong negative correlation with substrate resistance, which was the best predictor of curlew density. Curlews were most abundant at sites with the least resistant substrate, and these sites also generally had the highest prey density and biomass. When the effect of substrate resistance was statistically removed, curlew density was no longer significantly correlated with prey density and biomass. This suggests that broadscale habitat choice by Eastern Curlews on their non-breeding grounds is more strongly influenced by prey availability (which is higher when substrate resistance is lower) than by prey density or biomass, although in Moreton Bay a positive correlation across sites meant that these factors
were synergistic.
Finally, the present study tested whether foraging success could explain choice
of feeding sites by curlews. Foraging success was assessed at 11 of the 12 intertidal
flats described above. Biomass intake rate explained 57% of the variation in curlew
density across sites, and was a far better predictor of curlew density than either the
feeding or success rate. Both the biomass intake rate and curlew density were highest
on substrates with higher penetrability. There were some differences in feeding
behaviour between sexes, which were generally consistent with expectations given the
females’ greater body size and bill length, although neither sex had a clear energetic
advantage. The positive relationship between curlew density and biomass intake rate
was stronger than the previously-established positive relationship between curlew
density and substrate penetrability, suggesting that the curlews in Moreton Bay
choose feeding habitat directly on the basis of the food supply. Low aggression rates
suggest relatively little constraint from intraspecific competition during most of the
overwintering period. These results also suggest that the population of Eastern Curlews in Moreton Bay is not limited by the availability of food resources but perhaps by factors either on the breeding grounds or at stop-over sites during migration.
These findings indicate that, for assessing and monitoring the quality of feeding grounds for deep-probing shorebirds, a time-efficient measure of the physical properties of the substrate (such as penetrability) would be useful. Any structural modification of the curlews’ soft-sediment feeding flats that reduces substrate penetrability may inhibit successful foraging and be detrimental to them. Direct effects on the structure of soft sediments could come from activities including intertidal oyster farming, the compaction of sediments by vehicles and the dumping of rubbish.
In the present study, curlews foraged in a broad variety of habitats andconsumed a variety of different types and sizes of prey. Even impenetrable flats, delivering a low foraging success, were used for feeding by some birds. The use of their long bills to obtain many different types of prey...Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
CICS/School of Environment
Science, Environment, Engineering and Technology
Full Text
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Freudmann, Anita. "Phylogeography, habitat and resource use of Nyctimene robinsoni". Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/203859/1/Anita_Freudmann_Thesis.pdf.
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Fruit-eating bats play important roles in maintaining ecosystem health by contributing to seed dispersal and pollination. The current research aims to provide fundamental knowledge on the ecology and behaviour of the Queensland tube-nosed fruit bat (Nyctimene robinsoni). A field-based study investigated genetic variation across the currently known distribution range, and described habitat use, roosting ecology, foraging behaviour and dietary spectrum to evaluate the species' role as a seed disperser. Research outcomes contribute to a better understanding of the poorly understood group of Tube-nosed fruit bats, and findings can serve to support their conservation and species management.
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Tordoff, Ian Nigel Whitworth. "The distribution and dispersal of the dogwhelk Nucella lapillus in relation to habitat and community structure". Thesis, Bangor University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340957.
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Whitehead, Siân Carolyn. "Foraging behaviour and habitat use in the European starling, Sturnus vulgaris, in an agricultural environment". Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:74a0c54e-86a0-4cf4-ab26-d82b305febc6.
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Recent changes in agricultural practice have reduced the diversity of habitats for a number of bird species, including the European Starling Sturnus vulgaris. I investigated the distribution of a starling population on farmland, and related this distribution to the availability of suitable habitats by studying the foraging behaviour of individual birds. I observed a preference of the overwintering flock for established pasture fields, particularly those which were closer to the central roost, which had shorter grass and which provided feeding areas further from hedges. I also demonstrated the role of leatherjacket Tipula paludosa availabilities in influencing the starlings' choice of feeding site. These prey were shown experimentally to be preferred over earthworms Lumbricus spp. which were the other main type of invertebrate prey available. I was unable to detect any systematic temporal pattern of habitat use which could have been linked to an appropriate theoretical framework (e.g. Ideal Free Distribution). I investigated the impact of starling foraging on prey availability by observing the behaviour of captive starlings allowed to forage in small enclosures. These experiments indicated that, at the level of foraging pressure expected in natural flocks, there was no significant resource depression during a single flock feeding visit to any one site. Furthermore I proposed that the extent of resource depression during the winter was insufficient to cause a shift in the birds' choice of foraging habitat over this period. The apparent lack of effects of resource depression raised the question of why starlings did not feed in the most preferred fields all the time. Further enclosure experiments investigated how an individual's foraging success might be affected by feeding with conspecifics. I found no evidence for enhancement or depression of foraging success as a result of feeding where another bird had just previously foraged, and little evidence for an effect of feeding in the presence of two other birds, despite changes in vigilance and time spent fighting. A possibly greater heterogeneity of these effects when in the natural flock situation was considered in relation to the observed flock departures. These and other effects (e.g. sampling the environment) were discussed as possible causes for the observed flock movements between fields. A final enclosure experiment investigated the impact of starling foraging on prey availability during the breeding season and demonstrated significant resource depression in a preferred field over the chick-feeding period. I then discussed starling foraging and the availability of suitable habitats in relation to the documented population decline of this species.
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Robinson, Patrick William. "Exploiting pelagic habitat : navigation, migration, and foraging success in the northern elephant seal (Mirounga angustirostris) /". Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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Edwards, Ewan William James. "The breeding season distribution, foraging trip characteristics and habitat preference of northern fulmars, Fulmaris glacialis". Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230125.
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The role of seabirds as indicators of marine conditions is widely acknowledged. As top predators they are vulnerable to environmental change. The study of spatial ecology has been identified as critical to the conservation of seabirds. The studies described within this thesis have for the first time explored in detail the spatial distribution of breeding fulmars. A combination of geolocation (GLS) and GPS tracking during incubation and chick rearing found that fulmars ranged further and for longer during incubation, with little difference between the sexes (Chapter 2). GLS tracking data from this period suggested that some birds were foraging at the Mid Atlantic Ridge, far surpassing the assumed maximum foraging range of this species whilst breeding. This was confirmed from the GPS track of one bird. Search behavior during the trip suggests that this bird exploited prey resources associated with fronts at the Charlie Gibbs Fracture Zone (Chapter 4). Whilst foraging far from the breeding site may allow birds to avoid competition and exploit predictable prey patches, this wide ranging behaviour may expose birds to threats such as fisheries bycatch. The majority of female fulmars tracked during the pre laying exodus foraged within the Norwegian Sea (Chapter 3), where it is estimated that 20,000 fulmars die annually on longlines. A double-tagging study, the first in the North Atlantic region and the first on a petrel species, used a state-space model to estimate the error in GLS data from fulmars and reconstructed the most probably route travelled. These data indicate that during this early period of the breeding season when distribution was virtually unknown, fulmars from a Scottish colony were foraging widely within three broad biogeographical regions. Meanwhile, fine-scale GPS tracking data was collected at three colonies during the chick rearing period. When combined with environmental and fisheries data within a model this facilitated investigation into the habitat preference of fulmars, finding associations between fulmar presence and fisheries activity, as well as oceanography (Chapter 5). This thesis describes how the use of telemetry has for the first time linked breeding season foraging characteristics with spatial distribution and habitat. Tracking has revolutionized our knowledge of fulmar distribution, behavior and habitat preference during the breeding season.
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Chruszcz, Bryan. "Foraging and thermoregulatory behaviour of the long-eared bat (Myotis evotis) roosting in natural habitat". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ38573.pdf.
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Theel, Heather J. "HABITAT ALTERATION BY HYDRILLA AND ITS EFFECT ON MACROINVERTEBRATE COMMUNITY STRUCTURE AND BLUEGILL FORAGING EFFICIENCY". MSSTATE, 2007. http://sun.library.msstate.edu/ETD-db/theses/available/etd-03232007-083154/.
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Exotic invasive plant species can alter aquatic habitats potentially influencing the macroinvertebrate community and foraging fishes. Therefore, I investigated the hypothesis that Hydrilla verticillata will alter habitat important to macroinvertebrate community structure and bluegill foraging efficiency. Studies were conducted in ponds and aquaria. At the pond level, macroinvertebrate abundance, richness, and biomass in a hydrilla-dominated habitat did not differ significantly from a diverse plant habitat. Indicator taxa did differ significantly between respective treatments. The data suggest hydrilla beds may not provide increased macroinvertebrate abundance and richness compared to diverse plant beds as previously thought. In aquaria, habitat complexity (Ihv) and light transmittance were influenced by increasing the homogeneity of hydrilla in an aquatic bed habitat. In addition, bluegill foraging efficiency was affected negatively by increasing spatial complexity of a hydrilla dominated habitat. Therefore, a shift to a monotypic hydrilla habitat can alter macroinvertebrate community composition and impact bluegill foraging success.
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Guse, Nils [Verfasser]. "Habitat selection and foraging ecology of seabirds in the Gulf of St. Lawrence / Nils Guse". Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1036242862/34.
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Sawyer, Thomas R. "Habitat use and breeding performance in an inshore foraging seabird, the Black Guillemot Cepphus grylle". Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312131.
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Evans, Andrew David. "Individual differences in foraging behaviour, habitat selection and bill morphology of wintering curlew, Numenius arquata". Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/14801.
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Schmidt, Jason M. "Adaptive Foraging in a Generalist Predator: Implications of Habitat Structure, Density, Prey Availability and Nutrients". Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1312815757.
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St-Amand, Julien. "Foraging ecology of Endangered Williamson’s Sapsuckers in Canada : multi-scale habitat selection in two biogeoclimatic zones". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61088.
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Williamson’s Sapsuckers are Endangered woodpeckers in Canada that breed in montane forests only in British Columbia and require protection of their critical habitat. While there is reasonable knowledge of their distribution and nesting habitat requirements, there are knowledge gaps regarding foraging habitat of Williamson’s Sapsuckers. I investigated the selection of foraging habitat in managed forest at the foraging substrate and patch scales using visual observations of foraging behaviour of 27 radio-tagged Williamson’s Sapsuckers in the two biogeoclimatic zones where they are found in Canada, the Montane Spruce and Interior Douglas-fir. The characteristics of foraging trees differed with foraging mode and nesting status, but not with bird gender or age. Williamson’s Sapsuckers preferred large live Douglas-fir (> 22.5 cm dbh) for gleaning and sap feeding in both biogeoclimatic zones, while trees used for pecking were mostly large dying western larch in the Montane Spruce zone and large dead ponderosa pine in the Interior Douglas-fir zone. At the foraging patch scale, Williamson’s Sapsuckers did not prefer any stand-level characteristics in the Montane Spruce zone, while in the Interior Douglas-fir zone, they selected foraging patches with higher densities of their preferred foraging substrate (i.e., large live Douglas-fir). Areas of open habitat and single trees were avoided during foraging trips in both biogeoclimatic zones and this habitat type was found in significantly lower proportions in the Montane Spruce than in the Interior Douglas-fir zone. Williamson’s Sapsuckers showed no significant preferences for within-stand configuration characteristics (retained groups, forest edges, open stands and closed stands) in the Montane Spruce zone, but they preferred foraging along forest edges and in closed stands in the Interior Douglas-fir zone. I used foraging trip distances to recommend nest reserve (no-logging; 0-140 m from the nest) and nest management zones. For the nest management zone, I recommend only partial harvesting with retained groups of trees extending from 140-340 m in the Montane Spruce zone and from 140-410 m in the Interior Douglas-fir zone. My study on Williamson’s Sapsuckers is the first to provide a comprehensive representation of foraging habitat requirements for the species.Forestry, Faculty of
Graduate
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Bradshaw, Dana Seward. "Habitat Quality and Seasonal Foraging Patterns of the Red-Cockaded Woodpecker (Picoides borealis) in Southeastern Virginia". W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539625587.
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Wardle, Ryan N. "Phantom Ocean, Real Impact: Natural Surf Sound Experiments Alter Foraging Activity and Habitat Use Across Taxa". DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2239.
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A growing body of research focuses on how background sounds shape and alter critical elements of animals’ lives, such as foraging behavior, habitat use, and ecological interactions (Bradbury & Vehrencamp, 2011; Barber et al., 2010; Kight & Swaddle, 2011; Shannon et al., 2016). Much of this research has centered on the effects of anthropogenic noise (Dominoni et al., 2020; Francis & Barber, 2013; Ortega, 2012; Swaddle et al., 2015), but recent studies have also revealed that natural sound sources can influence animal behavior (Davidson et al., 2017; Le et al., 2019). Natural sounds, such as crashing surf, can create conditions where signaling and listening are difficult, but how this influences different species’ ecological interactions are unknown.
To study the effects of crashing surf sound we experimentally introduced landscape-level acoustic playbacks where surf sound was not naturally present to create a “phantom ocean”. Phantom ocean treatment sites were employed alongside higher frequency “shifted” treatment sites to test for frequency-dependent effects, “real ocean” sites where surf sound was endemic, and ambient control sites. The phantom and shifted treatments were played continuously during the spring and summer of 2017-2019. Within this acoustic experimental landscape we conducted multiple studies to test the effects of crashing surf sound on animal behavior, habitat use, and ecological interactions. Through an artificial caterpillar predation experiment modeled after Roslin et al. (2017), we found that when exposed to natural sound treatments the foraging activity of rodents and arthropods increased, while that of birds declined. A potential explanation for this pattern includes taxon-specific responses reflecting different perceived risk-reward trade-offs in natural sound conditions. To follow this up we performed occupancy modeling on data collected by camera traps set within our system. We observed different responses among groups of species with different functional roles in the community for both detection (p) and occupancy (Ψ) probabilities.
Our combined results indicate different species and functional groups have unique foraging behavior and patch use responses to natural sounds, likely based on their ecological interactions. Specifically, Cricetid rodents are likely more active in areas exposed to natural sounds, possibly due to lower perceived predation risk because mesocarnivores are less active. Insectivorous birds are also likely less active under natural sounds conditions, although the frequency of the sound, and the body size and diet of the bird appear influential. Together these findings suggest that natural sounds shape not only individual behavioral adjustments, but also multi-trophic, community level interactions. Our results show that natural sounds are an important driver of ecological interactions, but much remains to be uncovered. The mechanisms by which natural sounds influence individuals, populations, and many other aspects of ecology remain unexplored and provide fertile ground for future inquiry.
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Walli, Andreas G. "On the movements, aggregations and the foraging habitat of bluefin tuna (Thunnus thynnus & T. orientalis) /". Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.
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Amidon, Frederick A. "Habitat Relationships and Life History of the Rota Bridled White-eye (Zosterops rotensis)". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35991.
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The Rota bridled white-eye (Zosterops rotensis)(Aves, Passeriformes) has experienced a severe population decline and range restriction over the last four decades. Little is known about this species and factors involved in the decline and range restriction are unclear. This study examined the potential roles of habitat alteration, introduced black drongos (Dicrurus macrocercus), and introduced rats in the decline and gathered more information on the behavior and breeding biology of this species. New life history data were collected and Rota and Saipan bridled white-eyes were found to differ in nest site characteristics and some behaviors. The importance of habitat alteration was assessed by examining Rota bridled white-eye habitat relationships at the microhabitat, within-range, Sabana-wide, and island-wide levels. Rota bridled white-eyes show a preference for high elevation wet forest but what drives their distribution within their current range was unclear. However, the alteration of this forest type by supertyphoon Roy in 1988 was probably the major factor in the decline of Rota BWEs between 1982 and 1996. Black drongo and Rota bridled white-eye relationships were addressed using current and historical survey data. Black drongos were found to prey on Rota bridled white-eyes but they probably only played at most a partial role in the decline of the Rota bridled white-eye. Introduced rats densities were assessed in Rota bridled white-eye areas and on other areas of the island and no evidence for rat numbers limiting Rota bridled white-eyes to their current range was found.Master of Science
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Duverge, Paul Laurent. "Foraging activity, habitat use, development of juveniles, and diet of the greater horseshoe bat (Rhinolophus ferrumequinum - Schreber 1774) in south-west England". Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388116.
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Karlsson, Konrad. "The effect of visibility and predators on foraging efficiency in littoral and pelagic perch". Thesis, Uppsala universitet, Limnologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182653.
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Phenotypic plasticity in Eurasian perch (Perca fluviatilis) can be driven by a trade-off for ecological specialisation to littoral and pelagic resources. Previous studies on perch have found that this specialisation can have different effects on linkage between the littoral and pelagic food web depending on water transparency. In this study I aimed to answer how foraging efficiency and prey preference of phenotypic divergent perch are affected by high and low water transparency, and the presence of a predator in a series of aquarium experiments. Two different phenotypes of perch were kept in littoral and pelagic environments in the lab. By presenting perch with Daphnia sp. and Ephemeroptera, either separately or combined. I found that in clear water the littoral and pelagic phenotypes were comparatively more efficient on resources that were representative of their habitats (Ephemeroptera and Daphnia, respectively) and that both phenotypes prefer Ephemeroptera over Daphnia. In low visibility the differences in foraging efficiency between phenotypes when feeding on Daphnia disappeared but remained similar to clear water when feeding on Ephemeroptera. When vision was constrained littoral and pelagic perch showed no sign of prey preferences. In the presence of a predator the difference in foraging efficiency between the phenotypes, and also prey preference disappeared. I found that littoral phenotypes interacted more with other group members than did pelagic phenotypes, when foraging on littoral prey. And for perch in general, when foraging for Daphnia the interaction among group members was markedly reduced compared to when foraging for Ephemeroptera. In this study I show that morphological adaptation and prey choice is affected by visibility and predation. I also give suggestions how and argue why this can affect linkage of food webs and the community composition in littoral and pelagic habitats.
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Clay, Thomas Anthony. "Drivers of variation in the migration and foraging strategies of pelagic seabirds". Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/267809.
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The ability to move and forage efficiently plays a major role in determining the fate of individuals, and has important implications for population dynamics and ecosystem functioning. Migration is a particular type of movement strategy, whereby animals may travel remarkable distances in order to take advantage of seasonality in resource availability or to avoid arduous winter conditions; however, this can be at a cost in terms of increased mortality. Indeed, anthropogenic threats in non-breeding areas are a major cause of population declines and a better understanding of non-breeding spatial ecology is required in order to advance both ecological theory and conservation management. The recent development of animal tracking technologies, in particular light-based geolocation, has made it possible to track large-scale and long-term movements; however, there are still gaps in our knowledge, such as the links between migratory and reproductive performance, connectivity among populations and the ontogeny of migration strategies. In this thesis, I utilise multi-species and longitudinal datasets from albatrosses and petrels, some of the most mobile species on Earth, to explore the drivers of variation in movements, habitat use and foraging behaviour, and the implications for life history and conservation. In Chapter 1, I provide an overview of the key topics of this thesis. In Chapter 2, I provide quantitative recommendations of minimum sample sizes needed to track pelagic seabird migrations, using data from 10 species. In Chapter 3, I examine between- and within-population differences in the habitat preferences and distributions of albatrosses, including the relative roles of habitat specialization and intra-specific competition. In Chapter 4, I investigate the year-round movement and foraging strategies of petrels living in nutrient-poor environments. In Chapter 5, I examine potential links between foraging behaviour during the non-breeding season and reproductive senescence. In Chapter 6, I explore the ontogeny of foraging behaviour and foraging site fidelity in young albatrosses, shedding light on their “lost years” at sea. Finally, I conclude with a general discussion summarizing main findings and suggesting future work. Overall, my results highlight the complex relationships among individual traits, the environment, movements and foraging behaviour, and population dynamics across the lifespan of individuals, with implications for the conservation of this highly threatened group of species.
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Boyle, Alice. "Why do Birds Migrate? The Role of Food, Habitat, Predation, and Competition". Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195068.
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The ultimate causes of bird migration are largely unknown despite more than a century of research. By studying partially migratory short-distance tropical migrants and by employing comparative methods, some difficulties in testing hypotheses for evolution of migration can be overcome. Using comparative methods I tested the evolutionary precursor hypothesis, a major hypothesis for why migration evolved in some lineages and not in others. The results of this study conflicted with many assumptions and predictions of the evolutionary precursor hypothesis. Most importantly, migratory behavior was not related to diet and habitat in simple ways. The interaction between diet and habitat, as well as consistent associations between flocking behavior and migration suggested that food variability is poorly captured by the surrogates embodied in the evolutionary precursor hypothesis. I then employed comparative methods to studying tropical altitudinal migration. Comparisons of diets and fruit preferences between species pairs showed that migrants are more frugivorous, eat a broader diversity of fruits, and have diets that more strongly resemble their preferences than do residents. Although providing evidence that food limitation plays a role in altitudinal migration, these results do not support the hypothesis that interspecific competition explains variation in migratory behavior. Next, I provided the first test of a predation-based hypothesis to explain altitudinal migration. Migrants breed at higher elevations than where they spend their non-breeding season. Thus, birds may migrate uphill to escape high nest predation risk at lower elevations. Results from this experimental study are largely consistent with this hypothesis, but anomalies between predicted and observed patterns suggest that either migration of lowland birds occurs in response to other factors, or that anthropogenic change has altered the tradeoffs involved in migratory decisions. Finally, I focus on a single migrant species and evaluate (a) two food-based hypotheses to explain the destination of migration movements, and (b) mechanisms underlying intra-specific differences in migratory strategy. Food can explain why Corapipo altera migrate uphill, but not why they migrate downhill. My data on sex bias and body condition leads to a new hypothesis explaining the complete annual cycle of this tropical migrant bird.
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Garrison, Barrett A. "Avian population densities, habitat use, and foraging ecology in thinned and unthinned hardwood forests in Southwestern Virginia". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74151.
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I examined impacts of thinning on bird population densities and habitat use in Appalachian mixed-hardwood forests during 1984 and 1985 at three thinned and three unthinned stands in the Jefferson National Forest, southwestern Virginia. Densities of shrubs, saplings, trees, and snags, canopy and ground cover, and foliage volume were the structural variables most influenced by thinning. Populations of shrub/understory birds were higher in thinned stands than unthinned stands. Canopy-dwelling species showed variable population responses to thinning.
Habitat use similarities were used to group 13 bird species into three categories: (1) shrub/conifer species included the tufted titmouse, blue-gray gnatcatcher, wood thrush, ovenbird, and hooded warbler, (2) generalist species included the eastern wood-pewee, red-eyed vireo, black-and-white warbler, and scarlet tanager, and (3) mature/deciduous species included the white-breasted nuthatch, solitary vireo, blackburnian warbler, and worm-eating warbler. Shrub, snag, and conifer density and ground cover were the four habitat variables most important in separating used from unused sites.
Foraging behavior and resource use of seven bird species were examined in two thinned and two unthinned stands. No differences in foraging methods or niche breadth were found between the stands for all species. Differences in foraging and tree heights were due to tree height differences between the stands.
For most species, foraging resource use was equal to availability. Short, small diameter trees were rarely used. Oaks were used most often, and red maple and conifers were rarely used for foraging. The opportunistic nature of avian foraging behavior and the vegetative differences between thinned and unthinned stands led to the foraging differences noted.Master of Science