Carol L. McIntyre

Reproductive characteristics of migratory Golden Eagles in Denali National Park, Alaska

We describe reproductive characteristics of Golden Eagles (Aquila chrysaetos) breeding in Denali National Park, Alaska during an entire snowshoe hare (Lepus americanus) cycle, 1988-1997. Data on nesting eagles were collected at 58 to 72 nesting areas annually using two aerial surveys. Surveys were conducted during the incubation period to determine occupancy and nesting activities and late in the nestling period to count nestlings and determine nesting success. Annual occupancy rates of nesting areas did not vary significantly. whereas laying rates, success rates, and mean brood size varied significantly over the study period. Fledgling production for the study population varied sevenfold during the ten-year period. Laying rates, mean brood size, and overall population productivity were significantly correlated with abundance of cyclic snowshoe hare and Willow Ptarmigan (Lagopus lagopus) populations. Reproductive rates of Golden Eagles in Denali were similar to those of Golden Eagles from other high latitude study areas in North America, but lower than for Golden Eagles from temperate zone study areas in North America.

An adaptive-management framework for optimal control of hiking near golden eagle nests in Denali National Park.

Unintended effects of recreational activities in protected areas are of growing concern. We used an adaptive-management framework to develop guidelines for optimally managing hiking activities to maintain desired levels of territory occupancy and reproductive success of Golden Eagles (Aquila chrysaetos) in Denali National Park (Alaska, U.S.A.). The management decision was to restrict human access (hikers) to particular nesting territories to reduce disturbance. The management objective was to minimize restrictions on hikers while maintaining reproductive performance of eagles above some specified level. We based our decision analysis on predictive models of site occupancy of eagles developed using a combination of expert opinion and data collected from 93 eagle territories over 20 years. The best predictive model showed that restricting human access to eagle territories had little effect on occupancy dynamics. However, when considering important sources of uncertainty in the models, including environmental stochasticity, imperfect detection of hares on which eagles prey, and model uncertainty, restricting access of territories to hikers improved eagle reproduction substantially. An adaptive management framework such as ours may help reduce uncertainty of the effects of hiking activities on Golden Eagles.

Survival Probability and Mortality of Migratory Juvenile Golden Eagles from Interior Alaska

Abstract The conservation of golden eagles (Aquila chrysaetos) requires a thorough understanding of their demographic parameters. Productivity, commonly measured as the number of nestlings or fledglings per pair, is the parameter reported by most studies of nesting golden eagles and is often used as a measure of their population status. Survival may be an equally or more important parameter to measure; however, survival rates of golden eagles are not well documented. We used satellite telemetry to estimate the probability of first-year survival for migratory golden eagles raised in Denali National Park and Preserve, Alaska, USA. We calculated the probability of first-year survival using program MARK. Based on the best approximating model, monthly survival probability was 0.88 ± 0.04 (mean ± SE) during the autumn migration and early winter period for golden eagles marked in 1997 and 0.78 ± 0.05 during the same period for golden eagles marked in 1999. Monthly survival during the remaining 3 periods (i.e., late winter, spring migration, summer) was 0.94 ± 0.03 for both cohorts. Survival during the entire 11-month period was 0.34 ± 0.10 for the 1997 cohort and 0.19 ± 0.07 for the 1999 cohort. Causes of mortality included starvation, electrocution, and poaching. Our results indicate that low first-year survival may limit recruitment and we recommend that golden eagle monitoring programs include survival estimates.

Movements of Golden Eagles (Aquila chrysaetos) from Interior Alaska During Their First Year of Independence

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 km. Peak tracking velocities during spring migration reached 284 km day−1 in 1998 and 330 km day−1 in 2000. In contrast to juvenile Golden Eagles raised at temperate latitudes in North America, juveniles raised in Denali traveled thousands of kilometers across western North American during their first year of independence. Our results suggest that conservation strategies for migratory Golden Eagles from Denali, and perhaps from other areas in northern North America, require a continental approach. Movimientos de Individuos de Aquila chrysaetos desde el Interior de Alaska durante su Primer Año de Independencia

Perturbation analysis for patch occupancy dynamics

Perturbation analysis is a powerful tool to study population and community dynamics. This article describes expressions for sensitivity metrics reflecting changes in equilibrium occupancy resulting from small changes in the vital rates of patch occupancy dynamics (i.e., probabilities of local patch colonization and extinction). We illustrate our approach with a case study of occupancy dynamics of Golden Eagle (Aquila chrysaetos) nesting territories. Examination of the hypothesis of system equilibrium suggests that the system satisfies equilibrium conditions. Estimates of vital rates obtained using patch occupancy models are used to estimate equilibrium patch occupancy of eagles. We then compute estimates of sensitivity metrics and discuss their implications for eagle population ecology and management. Finally, we discuss the intuition underlying our sensitivity metrics and then provide examples of ecological questions that can be addressed using perturbation analyses. For instance, the sensitivity metrics lead to predictions about the relative importance of local colonization and local extinction probabilities in influencing equilibrium occupancy for rare and common species.

POSTFLEDGING DEPENDENCE PERIOD OF MIGRATORY GOLDEN EAGLES (AQUILA CHRYSAETOS) IN DENALI NATIONAL PARK AND PRESERVE, ALASKA

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). Período de Dependencia Posterior al Emplumamiento de Aquila chrysaetos en el Parque Nacional y Reserva Denali, Alaska

Quantifying Sources of Mortality and Wintering Ranges of Golden Eagles from Interior Alaska Using Banding and Satellite Tracking

Abstract Documenting the year-round movements and factors affecting the survival of wide-ranging birds is essential for developing effective conservation strategies. This is especially true for long-distance migratory species that spend much of their lives away from their breeding areas. Encounters of banded birds have provided information on the movements and survival of many bird species. More recently, telemetry studies provided new information on movements and survival of migratory birds. Golden Eagles (Aquila chrysaetos) raised in the higher latitudes of northwestern North America are usually migratory, but little is known about their year-round movements or survival. From 1988 to 2009, I banded 307 Golden Eagle nestlings in and near Denali National Park and Preserve in interior Alaska. From 1997 to 1999, I also deployed 90-g satellite transmitters on 48 of these eagles just before they fledged. Ten of the 307 banded eagles (3%) were encountered after the banding event, including five within 1 yr of banding. All encounters with banded eagles were >800 km from the banding location outside Alaska during winter or the migration season. All banded eagles were encountered <2 km from a road or human settlement and the primary sources of mortality were electrocution and shooting. In contrast, all recoveries of dead radio-tagged eagles (14) were >5 km from a road, and post-mortem necropsy indicated that all but one of these eagles died from starvation. Locations of banded eagles encountered in winter ranged from southern Alberta to north-central Mexico. Relocations of radio-tagged eagles in winter ranged from central Alberta to southeastern New Mexico. These results, despite small sample sizes, demonstrate how different marking and tracking tools can produce different results regarding the sources of mortality and the wintering range of Golden Eagles from the same study area. CUANTIFICACIÓN DE LAS FUENTES DE MORTALIDAD Y DE LOS RANGOS DE INVERNADA DEL ÁGUILA AQUILA CHRYSAETOS EN ALASKA UTILIZANDO ANILLAS Y RASTREO SATELITAL La documentación de los movimientos durante todo el año y de los factores que afectan la supervivencia de las aves con grandes rangos de distribución es esencial para el desarrollo de estrategias efectivas de conservación. Esto es especialmente cierto para las especies que migran grandes distancias y que pasan gran parte de sus vidas lejos de sus áreas de cría. Los encuentros de aves anilladas han proporcionado información sobre los movimientos y la supervivencia de muchas especies de aves. Más recientemente, los estudios de telemetría han proporcionado nueva información sobre los movimientos y la supervivencia de las aves migratorias. Las águilas Aquila chrysaetos que se criaron en las latitudes más altas del noroeste de América del Norte son generalmente migratorias, pero se sabe poco acerca de sus movimientos durante todo el año o sobre su supervivencia. De 1988 a 2009, anillé 307 polluelos del águila A. chrysaetos cerca del Parque Nacional y Reserva Denali en el interior de Alaska. De 1997 a 1999, también usé transmisores satelitales de 90 g en 48 de estas águilas, justo antes de que emplumaran. Diez de las 307 águilas anilladas (3%) se encontraron después del evento de anillamiento, entre ellas cinco dentro del año de anillamiento. Todos los encuentros con las águilas anilladas fueron a >800 km de la ubicación de anillamiento y se encontraron fuera de Alaska durante el invierno o la temporada de migración. Todas las águilas anilladas se encontraron a <2 km de una carretera o de asentamientos humanos y las fuentes principales de mortalidad fueron la electrocución y disparos. Por el contrario, todas las recuperaciones de los individuos muertos equipados con radiotransmisores (16) estuvieron a >5 km de una carretera, y el análisis post-mortem indicó que todas estas águilas, menos una, murieron de hambre. La ubicación de las águilas anilladas encontradas en invierno fue desde el sur de Alberta al centro-norte de México. La ubicación de las aves con transmisores durante el invierno fue desde el centro de Alberta al sudeste de Nuevo México. A pesar de los tamaños de muestra pequeños, estos resultados demuestran cómo diferentes herramientas de marcado y de seguimiento pueden producir resultados diferentes en cuanto a las fuentes de mortalidad y del rango de invernada de A. chrysaetos de la misma área de estudio.

Characteristics of the Landscape Surrounding Golden Eagle Nest Sites in Denali National Park and Preserve, Alaska

ABSTRACT Descriptions of landscape characteristics of Golden Eagle (Aquila chrysaetos) nesting territories and foraging areas in Alaska are generally broad and qualitative. To provide a basis for future studies on relationships between landscape characteristics and reproductive success, we described landscape characteristics within a 3000-m radius surrounding the geographic center of 36 Golden Eagle nesting territories in Denali National Park and Preserve, Alaska. Within the 3000-m territory cores, we delineated 27 unique land-cover types based on 11 unique types of vegetation cover and structure within four terrestrial physiographic zones: Alpine, Upland, Lowland, and Riparian. Rugged terrain, alpine areas, and a mosaic of land-cover types including Alpine Low Shrub, Alpine Barren, Upland Low Shrub, Riparian Barren, and Riparian Shrub characterized most territory cores. Alpine was the most common physiographic zone, and low shrub was the most common land-cover type in territory cores (x  =  68.5% area, 95% C.I.  =  61.2–75.5%). Our results should be useful for monitoring responses of breeding Golden Eagles to future changes in this landscape.

Genetic structure and viability selection in the golden eagle ( Aquila chrysaetos ), a vagile raptor with a Holarctic distribution

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.

DISPARITIES BETWEEN RESULTS AND CONCLUSIONS: DO GOLDEN EAGLES WARRANT SPECIAL CONCERN BASED ON MIGRATION COUNTS IN THE WESTERN UNITED STATES?

Abstract A recent summary of raptor migration count data concluded that the status of Golden Eagles (Aquila chrysaetos) in western North America warranted concern (Hoffman and Smith 2003). Our analysis of these data did not lead us to the same conclusion. We have three specific concerns. First, the regional characterizations of eagle migration in Hoffman and Smith (2003) are based on a very small sample of sites. Therefore, we recommend that these characterizations be considered as hypothetical in nature. Second, we suggest that the population cycles and patterns of age-specific population change described by Hoffman and Smith (2003) are neither as general nor as clear-cut as they indicated. Finally, although the authors expressed concern about the status of Golden Eagles based upon both their findings and data from other sources, we did not find compelling evidence for population declines in our inspection of those same data. Disparidad entre Resultados y Conclusiones: ¿Es el Estatus de Aquila chrysaetos Especialmente Preocupante de Acuerdo a los Conteos Migratorios del Oeste de los Estados Unidos? Resumen. Un resumen de los datos de conteos de migración de rapaces realizado recientemente concluyó que el estatus de Aquila chrysaetos en el oeste de Norte América es preocupante (Hoffman y Smith 2003). Nuestro análisis de los mismos datos no nos llevó a la misma conclusión, y tenemos tres inquietudes específicas. Primero, las caracterizaciones regionales de la migración de las águilas en Hoffman y Smith (2003) están basadas en una muestra de sitios muy pequeña. Por tanto, recomendamos que dichas caracterizaciones se consideren hipotéticas. Segundo, sugerimos que los ciclos poblacionales y los patrones de cambio poblacional edad-específicos descritos por Hoffman y Smith (2003) no son tan generales ni tan claros como ellos lo indicaron. Finalente, aunque los autores se manifestaron preocupados por el estatus de A. chrysaetos basándose en sus hallazgos y en datos de otras fuentes, al inspeccionar los mismos datos nosotros no encontramos evidencia contundente de que existan tales disminuciones poblacionales.