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Philip D Whitfield - One of the best experts on this subject based on the ideXlab platform.
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responses of dispersing gps tagged golden eagles Aquila Chrysaetos to multiple wind farms across scotland
Ibis, 2021Co-Authors: Alan H Fielding, Stuart Benn, Roy Dennis, Ewan Weston, David J Anderson, Matthew Geary, Philip D WhitfieldAbstract:This is the peer reviewed version of the following article: [Fielding, A. H., Anderson, D., Benn, S., Dennis, R., Geary, M., Weston, E., & Whitfield, D. P. (2021). Responses of dispersing GPS‐tagged Golden Eagles (Aquila Chrysaetos) to multiple wind farms across Scotland. Ibis, https://doi.org/10.1111/ibi.12996], which has been published in final form at [https://onlinelibrary.wiley.com/doi/10.1111/ibi.12996]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving
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a simple topographical model to predict golden eagle Aquila Chrysaetos space use during dispersal
Ibis, 2020Co-Authors: Alan H Fielding, Paul F Haworth, David Anderson, Stuart Benn, Roy Dennis, Ewan Weston, Philip D WhitfieldAbstract:Many large raptors exploit or rely on anabatic and orographic winds which provide vertical lift, to supplement or provide the energy fuelling flight. Airspace is therefore a critical habitat for such large raptors and its use is subject to the underlying terrestrial topography, because particular topographical features are more likely to provide wind‐energetic lift. Accordingly, ridges and/or ‘rugged topography’ are common preferred features in habitat use by large raptors. Our study aimed to provide a simple model of space use for a large raptor, the Golden Eagle Aquila Chrysaetos, based on thousands of GPS telemetry records during juvenile dispersal of 92 birds tagged as nestlings between 2007 and 2016 across upland Scotland. Model development was based on the hypothesis that four topographical variables would be influential: slope, aspect, altitude and distance from ridge. The telemetry dataset was divided into training and two testing components. The first testing set was derived by a temporal split resulting in approximately equal sample size on records and some temporal overlap in individuals’ records with training data. The second testing set involved no individuals from the training set. Aspect was removed early in training model development because it was not influential. The model found that young Golden Eagles preferred, or used according to availability, space above slopes greater than 10°, at an altitude of ≥ 300 m, and within 300 m of a ridge. The test data were highly correlated with those from the training data in the model variables, and performance as regard to expected preferences from the model was improved in both test datasets, indicating the model was robust. Given the apparent universal nature of large raptor dependence on topography, that topography is relatively immutable according to time and use, and that topographical data are readily available, we commend our approach to other habitat preference studies of Golden Eagles and other large raptors elsewhere.
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spatial distribution of undulating flight displays of territorial golden eagles Aquila Chrysaetos in lewis scotland
Bird Study, 2019Co-Authors: Robin Reid, Paul F Haworth, Alan H Fielding, Philip D WhitfieldAbstract:ABSTRACTCapsule: The undulating display flight of Golden Eagles Aquila Chrysaetos has a territorial function on current consensus: we found that displays could occur at any location within a home r...
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population structure and dispersal patterns in scottish golden eagles Aquila Chrysaetos revealed by molecular genetic analysis of territorial birds
Ibis, 2015Co-Authors: Rob Ogden, Elizabeth Heap, Ross Mcewing, Ruth Tingay, Philip D WhitfieldAbstract:Conservation management of species distributed across fragmented habitats requires consideration of population genetic structure and relative levels of genetic diversity throughout the relevant geographical range. The Golden Eagle Aquila Chrysaetos is monitored within Scotland to ensure its survival in the face of land-use pressure, persecution and future climate change. In this study we constructed DNA profiles for 271 individual birds using a collection of over 1600 moulted feathers collected from 148 territories, representing 34% of known Scottish territories in the largest population genetic study of Golden Eagles undertaken to date. The results, based on data from 10 nuclear microsatellite loci, revealed previously unreported genetic structure between the islands of the Outer Hebrides and the rest of Scotland (FST = 0.03), together with evidence of reduced genetic diversity in the Outer Hebridean population compared with mainland Scotland. Analysis of gene flow supports a hypothesis of limited, predominantly male-mediated, dispersal from the Outer Hebrides to mainland Scotland. The persistence of this pattern is discussed with respect to variation in population density and persecution pressure across Scotland. A finding of non-random mating within the Outer Hebrides is interpreted as evidence of natal philopatry that was revealed by more intensive sampling in these islands, and is likely to be accentuated by the apparent degree of isolation of the islands from the rest of Scotland.
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complex effects of habitat loss on golden eagles Aquila Chrysaetos
Ibis, 2006Co-Authors: Philip D Whitfield, Alan H Fielding, A G Gordon, David R A Mcleod, Mike J P Gregory, Paul F HaworthAbstract:The development of commercial forests presents potential threats to large raptors that rely on prey caught in open country. We examined the effect of afforestation of breeding habitat used by a population of Golden Eagles Aquila Chrysaetos in Scotland where, over the last 50 years, extensive stands of exotic conifers have been planted. Using data for 31 years on territory occupancy and breeding success, together with spatiotemporally dynamic mapping of forest cover and predicted areas of territory-use in a Geographical Information System, we examined relationships between forest cover and Eagle ecology at landscape and individual territory scales. Several territories were abandoned during the earliest phases of forest planting, but relatively few were apparently lost to later plantings. Territories with poorer breeding productivity appeared to be more vulnerable to abandonment than territories with better breeding productivity. At the landscape scale, temporal differences in breeding productivity were negatively related to the extent of forest cover, although productivity of individual territories showed no clear relationship with forest cover. Several territories with less than a 5% increase in forest cover experienced reduced productivity; however, territories least constrained by neighbouring pairs of Eagles showed an increase in productivity. Territories experiencing the greatest increases in forest cover showed a greater use of spatially separated nest-sites by occupying pairs. Hence, pairs that were less constrained by neighbours appeared to compensate for loss of open habitat by shifting their territory-use, whereas pairs that were more constrained could not compensate for open habitat loss and suffered reduced productivity (and, probably in some cases, abandoned the territory). We suggest that simple guidelines based on the extent and locations of habitat loss are inadequate when predicting effects on large territorial raptors such as Golden Eagles. Consideration should also be given to the 'quality' of a territory or occupying pair, as well as the extent to which territory-use is constrained by neighbouring pairs or other 'unsuitable habitat' which may have been affected by previous episodes of open habitat loss.
Alan H Fielding - One of the best experts on this subject based on the ideXlab platform.
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responses of dispersing gps tagged golden eagles Aquila Chrysaetos to multiple wind farms across scotland
Ibis, 2021Co-Authors: Alan H Fielding, Stuart Benn, Roy Dennis, Ewan Weston, David J Anderson, Matthew Geary, Philip D WhitfieldAbstract:This is the peer reviewed version of the following article: [Fielding, A. H., Anderson, D., Benn, S., Dennis, R., Geary, M., Weston, E., & Whitfield, D. P. (2021). Responses of dispersing GPS‐tagged Golden Eagles (Aquila Chrysaetos) to multiple wind farms across Scotland. Ibis, https://doi.org/10.1111/ibi.12996], which has been published in final form at [https://onlinelibrary.wiley.com/doi/10.1111/ibi.12996]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving
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a simple topographical model to predict golden eagle Aquila Chrysaetos space use during dispersal
Ibis, 2020Co-Authors: Alan H Fielding, Paul F Haworth, David Anderson, Stuart Benn, Roy Dennis, Ewan Weston, Philip D WhitfieldAbstract:Many large raptors exploit or rely on anabatic and orographic winds which provide vertical lift, to supplement or provide the energy fuelling flight. Airspace is therefore a critical habitat for such large raptors and its use is subject to the underlying terrestrial topography, because particular topographical features are more likely to provide wind‐energetic lift. Accordingly, ridges and/or ‘rugged topography’ are common preferred features in habitat use by large raptors. Our study aimed to provide a simple model of space use for a large raptor, the Golden Eagle Aquila Chrysaetos, based on thousands of GPS telemetry records during juvenile dispersal of 92 birds tagged as nestlings between 2007 and 2016 across upland Scotland. Model development was based on the hypothesis that four topographical variables would be influential: slope, aspect, altitude and distance from ridge. The telemetry dataset was divided into training and two testing components. The first testing set was derived by a temporal split resulting in approximately equal sample size on records and some temporal overlap in individuals’ records with training data. The second testing set involved no individuals from the training set. Aspect was removed early in training model development because it was not influential. The model found that young Golden Eagles preferred, or used according to availability, space above slopes greater than 10°, at an altitude of ≥ 300 m, and within 300 m of a ridge. The test data were highly correlated with those from the training data in the model variables, and performance as regard to expected preferences from the model was improved in both test datasets, indicating the model was robust. Given the apparent universal nature of large raptor dependence on topography, that topography is relatively immutable according to time and use, and that topographical data are readily available, we commend our approach to other habitat preference studies of Golden Eagles and other large raptors elsewhere.
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spatial distribution of undulating flight displays of territorial golden eagles Aquila Chrysaetos in lewis scotland
Bird Study, 2019Co-Authors: Robin Reid, Paul F Haworth, Alan H Fielding, Philip D WhitfieldAbstract:ABSTRACTCapsule: The undulating display flight of Golden Eagles Aquila Chrysaetos has a territorial function on current consensus: we found that displays could occur at any location within a home r...
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diet specificity is not associated with increased reproductive performance of golden eagles Aquila Chrysaetos in western scotland
Ibis, 2009Co-Authors: D P Whitfield, Paul F Haworth, Robin Reid, Ruth Tingay, Mike Madders, Mick Marquiss, Alan H FieldingAbstract:Amongst raptor species, individuals with specialized diets are commonly observed to have higher reproductive output than those with general diets. A suggested cause is that foraging efficiency benefits accrue to diet specialists. This diet specificity hypothesis thus predicts that diet breadth and reproductive success should be inversely related within species. We highlight, however, that a prey availability hypothesis also makes the same prediction in some circumstances. Hence, when high diet specificity results from high encounter rates with an abundant, preferred prey, then prey availability may affect reproductive success, with diet specialization as an incidental correlate. Using three insular study areas in western Scotland, we examine diet specificity and reproductive success in Golden Eagles Aquila Chrysaetos. Diet breadth and breeding productivity were not negatively related in any of our study areas, even though birds with specific diets did tend to have a higher incidence of preferred prey (grouse and lagomorphs) in the diet. Indeed, in two study areas there was evidence that diet generalists had higher breeding productivity. Our results therefore failed to support the diet specificity hypothesis but were consistent with the prey availability hypothesis. We highlight that although many other studies are superficially consistent with the diet specificity hypothesis, our study is not alone in failing to provide support and that the hypothesis does not provide a generic explanation for all relevant results. Diet specificity in predators can be at least partially a response to prey diversity, availability and distribution, and benefits associated with different prey types, so that being a generalist is not necessarily intrinsically disadvantageous. We suggest that the available evidence is more consistent with variation in prey abundance and availability as a more influential factor explaining spatial and temporal variation in breeding productivity of 'generalist' species such as the Golden Eagle. Under this argument, prey abundance and availability are the main drivers of variation in reproductive output. Diet specificity is a consequence of variation in prey availability, rather than a substantial cause of variation in reproductive success.
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complex effects of habitat loss on golden eagles Aquila Chrysaetos
Ibis, 2006Co-Authors: Philip D Whitfield, Alan H Fielding, A G Gordon, David R A Mcleod, Mike J P Gregory, Paul F HaworthAbstract:The development of commercial forests presents potential threats to large raptors that rely on prey caught in open country. We examined the effect of afforestation of breeding habitat used by a population of Golden Eagles Aquila Chrysaetos in Scotland where, over the last 50 years, extensive stands of exotic conifers have been planted. Using data for 31 years on territory occupancy and breeding success, together with spatiotemporally dynamic mapping of forest cover and predicted areas of territory-use in a Geographical Information System, we examined relationships between forest cover and Eagle ecology at landscape and individual territory scales. Several territories were abandoned during the earliest phases of forest planting, but relatively few were apparently lost to later plantings. Territories with poorer breeding productivity appeared to be more vulnerable to abandonment than territories with better breeding productivity. At the landscape scale, temporal differences in breeding productivity were negatively related to the extent of forest cover, although productivity of individual territories showed no clear relationship with forest cover. Several territories with less than a 5% increase in forest cover experienced reduced productivity; however, territories least constrained by neighbouring pairs of Eagles showed an increase in productivity. Territories experiencing the greatest increases in forest cover showed a greater use of spatially separated nest-sites by occupying pairs. Hence, pairs that were less constrained by neighbours appeared to compensate for loss of open habitat by shifting their territory-use, whereas pairs that were more constrained could not compensate for open habitat loss and suffered reduced productivity (and, probably in some cases, abandoned the territory). We suggest that simple guidelines based on the extent and locations of habitat loss are inadequate when predicting effects on large territorial raptors such as Golden Eagles. Consideration should also be given to the 'quality' of a territory or occupying pair, as well as the extent to which territory-use is constrained by neighbouring pairs or other 'unsuitable habitat' which may have been affected by previous episodes of open habitat loss.
David R A Mcleod - One of the best experts on this subject based on the ideXlab platform.
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complex effects of habitat loss on golden eagles Aquila Chrysaetos
Ibis, 2006Co-Authors: Philip D Whitfield, Alan H Fielding, A G Gordon, David R A Mcleod, Mike J P Gregory, Paul F HaworthAbstract:The development of commercial forests presents potential threats to large raptors that rely on prey caught in open country. We examined the effect of afforestation of breeding habitat used by a population of Golden Eagles Aquila Chrysaetos in Scotland where, over the last 50 years, extensive stands of exotic conifers have been planted. Using data for 31 years on territory occupancy and breeding success, together with spatiotemporally dynamic mapping of forest cover and predicted areas of territory-use in a Geographical Information System, we examined relationships between forest cover and Eagle ecology at landscape and individual territory scales. Several territories were abandoned during the earliest phases of forest planting, but relatively few were apparently lost to later plantings. Territories with poorer breeding productivity appeared to be more vulnerable to abandonment than territories with better breeding productivity. At the landscape scale, temporal differences in breeding productivity were negatively related to the extent of forest cover, although productivity of individual territories showed no clear relationship with forest cover. Several territories with less than a 5% increase in forest cover experienced reduced productivity; however, territories least constrained by neighbouring pairs of Eagles showed an increase in productivity. Territories experiencing the greatest increases in forest cover showed a greater use of spatially separated nest-sites by occupying pairs. Hence, pairs that were less constrained by neighbours appeared to compensate for loss of open habitat by shifting their territory-use, whereas pairs that were more constrained could not compensate for open habitat loss and suffered reduced productivity (and, probably in some cases, abandoned the territory). We suggest that simple guidelines based on the extent and locations of habitat loss are inadequate when predicting effects on large territorial raptors such as Golden Eagles. Consideration should also be given to the 'quality' of a territory or occupying pair, as well as the extent to which territory-use is constrained by neighbouring pairs or other 'unsuitable habitat' which may have been affected by previous episodes of open habitat loss.
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spatial association as an indicator of the potential for future interactions between wind energy developments and golden eagles Aquila Chrysaetos in scotland
Biological Conservation, 2006Co-Authors: Alan H Fielding, Philip D Whitfield, David R A McleodAbstract:Despite their environmental benefits in generating electricity without emission of ‘greenhouse’ gases, wind farms have attracted controversy with regard to their impacts on birds, especially golden eagles Aquila Chrysaetos. Evidence from USA studies suggest eagle fatalities through collision with turbines may be the main potential impact whereas for breeding eagles in Scotland, displacement from wind farm areas (indirect habitat loss) may be the primary impact. In this study, we examined the co-occurrence potential for golden eagles and wind farms in Scotland by documenting the spatial association between wind farm proposals and breeding eagle territories and areas potentially suitable for non-breeding eagles. Although there were records for over 500 wind farm proposals at various stages of development, relatively few coincided with eagle territories (ca. 4% of territories had a proposal within 3 km of territory centre). Similarly, only 2% of habitat predicted to be suitable for non-breeding eagles overlapped with proposed or installed wind farm areas. Moreover, estimates of the potential for electricity generation from all wind farm proposals, with respect to government targets for renewable energy supplies, suggested most proposals were unlikely to be constructed. We conclude that in comparison with other constraints on Scotland’s golden eagles, notably persecution, wind farms should not represent a serious concern if best practice in planning their location and minimising their impact are maintained. Potential future regional pressures on breeding eagles from wind farms are highlighted, however, and uncertainty of impact with respect to displacement or collision fatalities requires continued scrutiny.
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predicting home range use by golden eagles Aquila Chrysaetos in western scotland
2002Co-Authors: David R A Mcleod, Philip D Whitfield, Alan H Fielding, Paul F Haworth, M J McgradyAbstract:The conservation and management of golden eagles Aquila Chrysaetos requires information on home range, which is expensive and time-consuming to collect. We describe modelling techniques for predicting golden eagle ranging behaviour within a Geographic Information System (GIS). The model, called PAT (Predicting Aquila Territory), used data on ranging behaviour and geospatial factors from two areas of western Scotland. A range centre was estimated from the weighted mean nest site location in the past ten years. Range boundaries were estimated from Thiessen polygons, in the presence of neighbouring ranges, and a maximum ranging distance generated from parameters responsive to local range density, in the absence of neighbouring ranges. The model assumed that eagles did not use the sea or freshwater bodies, and avoided areas of human activity and closed canopy forests. The model also assumed that golden eagles preferred areas close to ridges (and other convex terrain features) and close to the centre of the range. The model output, at 50 × 50 m resolution, was three-dimensional with geographical location as x and y co-ordinates and use as a percentage of total home range use as the z co-ordinate. Comparison of the model’s predictions against range use observations suggested that it provided a good fit to observed range use. The PAT model has many potential applications, including the prediction of the likely impact of local developments such as windfarms and commercial forest expansion on territorial eagles and for providing information useful to managing land use change to the be
Todd E. Katzner - One of the best experts on this subject based on the ideXlab platform.
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summer and winter space use and home range characteristics of golden eagles Aquila Chrysaetos in eastern north america
The Condor, 2017Co-Authors: Tricia A Miller, Todd E. Katzner, Robert P Brooks, Michael Lanzone, Jeff Cooper, Kieran Omalley, David Brandes, Adam E DuerrAbstract:ABSTRACT Movement behavior and its relationship to habitat provide critical information toward understanding the effects of changing environments on birds. The eastern North American population of Golden Eagles (Aquila Chrysaetos) is a genetically distinct and small population of conservation concern. To evaluate the potential responses of this population to changing landscapes, we calculated the home range and core area sizes of 52 eagles of 6 age–sex classes during the summer and winter seasons. Variability in range size was related to variation in topography and open cover, and to age and sex. In summer, eagle ranges that were smaller had higher proportions of ridge tops and open cover and had greater topographic roughness than did larger ranges. In winter, smaller ranges had higher proportions of ridge tops, hillsides and cliffs, and open cover than did larger ranges. All age and sex classes responded similarly to topography and open cover in both seasons. Not surprisingly, adult eagles occupied the s...
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Genetic structure and viability selection in the golden eagle (Aquila Chrysaetos), a vagile raptor with a Holarctic distribution
Conservation Genetics, 2016Co-Authors: Jacqueline M. Doyle, Brian A. Millsap, Carol L Mcintyre, Todd E. Katzner, Gary W. Roemer, James W. Cain, Sarah A. Sonsthagen, Nadia B. Fernandez, Maria Wheeler, Zafer BulutAbstract:Molecular markers can reveal interesting aspects of organismal ecology and evolution, especially when surveyed in rare or elusive species. Herein, we provide a preliminary assessment of golden eagle ( Aquila Chrysaetos ) population structure in North America using novel single nucleotide polymorphisms (SNPs). These SNPs included one molecular sexing marker, two mitochondrial markers, 85 putatively neutral markers that were derived from noncoding regions within large intergenic intervals, and 74 putatively nonneutral markers found in or very near protein-coding genes. We genotyped 523 eagle samples at these 162 SNPs and quantified genotyping error rates and variability at each marker. Our samples corresponded to 344 individual golden eagles as assessed by unique multilocus genotypes. Observed heterozygosity of known adults was significantly higher than of chicks, as was the number of heterozygous loci, indicating that mean zygosity measured across all 159 autosomal markers was an indicator of fitness as it is associated with eagle survival to adulthood. Finally, we used chick samples of known provenance to test for population differentiation across portions of North America and found pronounced structure among geographic sampling sites. These data indicate that cryptic genetic population structure is likely widespread in the golden eagle gene pool, and that extensive field sampling and genotyping will be required to more clearly delineate management units within North America and elsewhere.
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the genome sequence of a widespread apex predator the golden eagle Aquila Chrysaetos
PLOS ONE, 2014Co-Authors: Jacqueline M. Doyle, Peter H Bloom, Todd E. Katzner, Bhagya K Wijayawardena, Andrew J DewoodyAbstract:Biologists routinely use molecular markers to identify conservation units, to quantify genetic connectivity, to estimate population sizes, and to identify targets of selection. Many imperiled eagle populations require such efforts and would benefit from enhanced genomic resources. We sequenced, assembled, and annotated the first eagle genome using DNA from a male golden eagle (Aquila Chrysaetos) captured in western North America. We constructed genomic libraries that were sequenced using Illumina technology and assembled the high-quality data to a depth of ~40x coverage. The genome assembly includes 2,552 scaffolds >10 Kb and 415 scaffolds >1.2 Mb. We annotated 16,571 genes that are involved in myriad biological processes, including such disparate traits as beak formation and color vision. We also identified repetitive regions spanning 92 Mb (~6% of the assembly), including LINES, SINES, LTR-RTs and DNA transposons. The mitochondrial genome encompasses 17,332 bp and is ~91% identical to the Mountain Hawk-Eagle (Nisaetus nipalensis). Finally, the data reveal that several anonymous microsatellites commonly used for population studies are embedded within protein-coding genes and thus may not have evolved in a neutral fashion. Because the genome sequence includes ~800,000 novel polymorphisms, markers can now be chosen based on their proximity to functional genes involved in migration, carnivory, and other biological processes.
Carol L Mcintyre - One of the best experts on this subject based on the ideXlab platform.
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Genetic structure and viability selection in the golden eagle (Aquila Chrysaetos), a vagile raptor with a Holarctic distribution
Conservation Genetics, 2016Co-Authors: Jacqueline M. Doyle, Brian A. Millsap, Carol L Mcintyre, Todd E. Katzner, Gary W. Roemer, James W. Cain, Sarah A. Sonsthagen, Nadia B. Fernandez, Maria Wheeler, Zafer BulutAbstract:Molecular markers can reveal interesting aspects of organismal ecology and evolution, especially when surveyed in rare or elusive species. Herein, we provide a preliminary assessment of golden eagle ( Aquila Chrysaetos ) population structure in North America using novel single nucleotide polymorphisms (SNPs). These SNPs included one molecular sexing marker, two mitochondrial markers, 85 putatively neutral markers that were derived from noncoding regions within large intergenic intervals, and 74 putatively nonneutral markers found in or very near protein-coding genes. We genotyped 523 eagle samples at these 162 SNPs and quantified genotyping error rates and variability at each marker. Our samples corresponded to 344 individual golden eagles as assessed by unique multilocus genotypes. Observed heterozygosity of known adults was significantly higher than of chicks, as was the number of heterozygous loci, indicating that mean zygosity measured across all 159 autosomal markers was an indicator of fitness as it is associated with eagle survival to adulthood. Finally, we used chick samples of known provenance to test for population differentiation across portions of North America and found pronounced structure among geographic sampling sites. These data indicate that cryptic genetic population structure is likely widespread in the golden eagle gene pool, and that extensive field sampling and genotyping will be required to more clearly delineate management units within North America and elsewhere.
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observations of migrating golden eagles Aquila Chrysaetos in eastern interior alaska offer insights on population size and migration monitoring
Journal of Raptor Research, 2016Co-Authors: Carol L Mcintyre, Stephen B LewisAbstract:Abstract Migratory Golden Eagles (Aquila Chrysaetos) from Alaska winter across a vast region of western North America, much of which is undergoing rapid change from a diversity of indirect and direct human activities. To address recent conservation concerns, we are studying the year-round movements of migratory Golden Eagles from interior and northern Alaska to identify and evaluate potential risks to their survival. We are also developing new survey techniques to estimate population size and trends. As part of our ongoing studies, we observed migrating Golden Eagles in spring and autumn 2014 during field investigations to locate Golden Eagle capture sites in eastern interior Alaska, and in spring 2015 during capture activities. We observed large numbers of Golden Eagles in both spring and autumn, suggesting that the Mentasta Mountains are an important migration corridor for this species. Further, our observations, including 1364 migrating Golden Eagles in October 2014, suggested that the Alaska Golden Ea...
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ecological and environmental correlates of territory occupancy and breeding performance of migratory golden eagles Aquila Chrysaetos in interior alaska
Ibis, 2012Co-Authors: Carol L Mcintyre, Joshua H SchmidtAbstract:Understanding relationships between environmental conditions and reproductive parameters is important when interpreting variation in animal population size. The northwestern North American population of Golden Eagles Aquila Chrysaetos canadensis initiates courtship and nesting in early spring when prey diversity is low and weather conditions are severe. Snowshoe Hare Lepus americanus and Willow Ptarmigan Lagopus lagopus, the primary prey of Golden Eagles early in their nesting season in interior Alaska, both exhibit cyclical fluctuations in abundance, providing the opportunity to investigate such relationships. We used Bayesian hierarchical models to explore variation in territory occupancy, nesting rates, nesting success and productivity of Golden Eagles from 1988 to 2010 in Denali National Park and Preserve, Alaska, in relation to annual and sitespecific parameters including prey abundance, weather conditions, elevation and human activity. We also investigated the long-term fluctuations of breeding performance over the course of the study. The abundance of Hares influenced both the number of Eagles that laid eggs and the number of Eagles that produced fledglings. The conditions on the breeding ground did not explain observed declines in nesting rates and fledgling production, suggesting that other factors such as change in the age structure of the population, increased intraspecific competition or deterioration of migration and wintering habitat are driving the long-term trends of these parameters.
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movements of golden eagles Aquila Chrysaetos from interior alaska during their first year of independence
The Auk, 2008Co-Authors: Carol L Mcintyre, David C Douglas, Michael W CollopyAbstract:Abstract We used satellite telemetry to study year-round movements of two cohorts of juvenile Golden Eagles (Aquila Chrysaetos) from Denali National Park and Preserve, Alaska. Radiotagged Golden Eagles started autumn migration between 15 September and 5 October and arrived on their winter areas 31 to 86 days later. Cumulative tracking distances during autumn migration ranged from 818 to 4,815 km. Peak tracking velocities during autumn migration reached 261 km day−1 in 1997 and 472 km day−1 in 1999. Golden Eagles wintered from southern Yukon Territory to southern New Mexico, and most spent the winter within 75 km of the location where they terminated their autumn migration. Spring migration occurred from late March through mid-June. Eagles showed little fidelity to their autumn migration paths as they migrated northwest in spring through western Canada and into Alaska. Duration of spring migration ranged from 24 to 54 days, and cumulative tracking distance during spring migration ranged from 2,032 to 4,491...
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postfledging dependence period of migratory golden eagles Aquila Chrysaetos in denali national park and preserve alaska
The Auk, 2006Co-Authors: Carol L Mcintyre, Michael W CollopyAbstract:Abstract The postfledging dependence period is not well documented for many species of raptors, including Golden Eagles (Aquila Chrysaetos). From 1997 to 1999, we used satellite telemetry to estimate the length of the postfledging dependence period, and the finite survival rate of fledglings during that period, for migratory Golden Eagles in Denali National Park and Preserve, Alaska. Length of the postfledging dependence period averaged 50.1 days and ranged from 39 to 63 days. The post- fledging dependence period was longer for Golden Eagles that hatched earlier, but hatching date did not influence the date they departed their natal area. Average date of departure from the natal area was 25 September. The departure period spanned a 17-day period from 15 September to 5 October, and coincided with a series of environmental changes including decreases in day length, temperature, and prey diversity. Probability of survival during the postfledging dependence period was 0.98 (95% CI = 0.94 to 1.00). Periodo de ...