Resumen El empetrolado de las aves puede tener consecuencias importantes a nivel individual y poblacional. Aunque la mayoria de los ejemplos publicados sobre empetrolado se refieren a la exposicion a fuentes antropicas de hidrocarburos, el empetrolado puede ocurrir naturalmente. Describimos cuatro casos de empetrolado natural de siete pollos de Aquila chrysaetos asi como nuestra intervencion para mitigarlo. En todos los casos, el aceite en estas aves provino casi seguro de sus presas, en su mayoria ardillas terrestres (Otospermophilus beecheyi), aportadas por aguilas adultas en cantidades mayores de las que los polluelos podian consumir. Algunos pollos solo fueron empetrolados levemente. Otros fueron empetrolados tanto que la funcion de las plumas se vio comprometida a un nivel en el que, sin nuestra intervencion, la supervivencia de estos pollos de aguila seguramente hubiera sido afectada. Hasta donde sabemos, este es el primer informe publicado sobre empetrolado de rapaces como consecuencia de un sobre ...

Cooper's Hawks (Accipiter cooperii) from approximately the northern third of the species' breeding range are considered migratory, hawks in the central portion are either migratory or resident, and hawks farther south are believed to be nonmigratory. We compared long-distance movements (>100 km between natal nest and encounter location) of Cooper's Hawks banded as nestlings at two different ranges of latitudes (>35 degrees and <35 degrees N). Our goal was to determine whether long-distance movements indicate that Cooper's Hawks from southern latitudes (south of 35 degrees N) are migrator and whether any migrate north, as do Bald Eagles (Haliaeetus leucocephalus) from several locations in the southern U.S.A. and Red-tailed Hawks (Buteo jamaicensis) from southern California. Long-distance movements by hawks banded as nestlings north of 35 degrees N were strongly oriented to the south, with only 17% in a northerly direction. The only hawks encountered >100 km from nests south of 35 degrees N were from southern Arizona and southern California. As opposed to the strong southward orientation of long-distance movements of hawks from north of 35 degrees N, mean direction south of 35 degrees was bipolar. Northward long-distance movements from nests in southern Arizona were relatively short (<200 km), while southward movements were substantially longer (1637 km in one case). Three Cooper's Hawks from southern Arizona were encountered in central Mexico, well south of the known breeding range, which suggests some individuals from southern Arizona are migratory. The pattern of long-distance movements from southern California was the reverse of that from southern Arizona. Most long-distance movements toward the south from southern California nests were comparatively short, whereas the three longest movements from that area (616-993 km) were to the north. Although tentative, we believe these longer movements are indicative of northward migration rather than natal or breeding dispersal.

Capsule: Global Positioning System (GPS)-tagged adult Golden Eagles Aquila chrysaetos breeding in forests in northern Sweden selected clear-cuts, coniferous forests with lichens and steep slopes during the breeding season but avoided wetlands and mixed forest.Aims: To investigate the habitat selection patterns of tree-nesting Golden Eagles, and identify how potential conflicts with wind farm development could be minimized.Methods: The study is based on GPS tracking data from 22 adult eagles. We estimated home range sizes using a biased random bridge approach and habitat selection patterns using resource selection functions following a use-availability design.Results: Core home range size among adults was variable during the breeding season (5-30 km(2)). Individual movement extents were variable, but sexes did not significantly differ in their scale of movement. At the landscape scale, individuals selected for clear-cuts and coniferous forest with ground lichens, whereas wetland, water bodies and mixed forest were avoided. Steeper and south facing slopes were selected for, whereas, north facing slopes were avoided.Conclusions: Potential conflicts between eagles and wind energy establishment can be reduced if wind farms are placed away from steep slopes, minimizing areas that are clear-cut during construction, and locating turbines within dense, young and other less favoured forest habitats.

Existen numerosos métodos y dispositivos disponibles para la captura de especies de rapaces de gran tamaño, pero la efectividad relativa de estas metodologías está pobremente documentada en la literatura. Como parte de varias propuestas de desarrollo de proyectos de energía eólica en el norte de Suecia, intentamos capturar individuos adultos de Aquila chrysaetos dentro de sus territorios de cría para colocarles transmisores. Nuestros intentos de captura se realizaron a finales de otoño y comienzos de invierno en el norte de Suecia, cuando los individuos de A. chrysaetos se alimentan a menudo de despojos dejados por cazadores y de cadáveres producto de colisiones con vehículos. Debido a las restricciones en Escandinavia respecto del uso de animales vivos como cebo, la selección de trampas se limitó a aquellos tipos de trampa que funcionan exitosamente con carroña. Por este motivo, utilizamos redes de arco basados en la existencia de experiencias previas exitosas con carroña, la facilidad de su transporte y la rapidez de su armado. Normalmente operamos de dos a tres trampas en 2010 y de tres a cuatro trampas en 2011, totalizando 120 días-trampa (54 en 2010 y 66 en 2011) en escondites durante un total de 993 horas (400 en 2010 y 593 en 2011). Capturamos 30 (8 en 2010 y 22 en 2011) individuos adultos de A. chrysaetos en 16 territorios. La mayor tasa de captura ocurrió en septiembre, previo a la dispersión de los jóvenes y antes de que algunos adultos se dispersaran de sus territorios de cría.

With a breeding range extending from approximately 68 degrees N in northern Canada to 8 degrees N in Panama, Red-tailed Hawks (Buteo jamaicensis) exhibit migrations that vary substantially with latitude. Northern populations are almost completely migratory, middle-latitude populations are partially migratory, and southern populations south of 38 degrees N are considered sedentary. Contrary to the latter widely held belief, we found that many juveniles and young adults from one population below 38 degrees N are also partially migratory. However, unlike most birds in the northern hemisphere that migrate south in autumn, young Red-tailed Hawks from our southwestern California study area migrated north in summer to summering areas as far as 1462 km from their natal nests. Of the 5271 Red-tailed Hawk nestlings we banded in the study area and an additional 189 banded by other researchers, 205 were encountered (found dead or alive or recaptured) outside the study area. We classified 64 encountered hawks as potential migrants, most (69%) of which were encountered to the north of their natal nest (median = 383 km). We found that juveniles and young adults banded south of 35 degrees N in the Pacific Flyway migrated north, whereas those banded north of 40 degrees N migrated south. Sixteen hawks from the study area equipped with satellite transmitters as fledglings migrated north (range 342-24 degrees) in summer, up to 1388 km, and returned to their natal region in autumn of the same year. This pattern was repeated annually until they acquired a mate and territory. Our results showed that many or most young Red-tailed Hawks migrate northward in the summer, and we propose that this pattern may be a response to historical climate changes, seasonal changes in sciurid prey availability, and/or dominance of territorial adults.

We studied home-range size using 15 GPS-tracked adult Golden Eagles (Aquila chrysaetos) in nine different territories, two in 2011 and those two as well as seven others in 2012, in northern Sweden. Home ranges were represented by 50 and 95% minimum convex polygons (MCPs) and 50, 80 and 95% kernel density estimates (KDE). In 2012, 95% MCPs ranged from 100-525 km(2) for males (n = 8), and 60-605 km(2) for females (n = 7). Mean home-range sizes for the eagles in our study were among the largest reported. Moreover, we found an inverse relationship between home-range size and the percent of clear-cuts within the range. Together these suggest that eagles in Sweden may compensate for low availability of hunting areas, e.g., lower proportion of clear-cuts in their range, by expanding their range. Some eagles displayed different forms of post-nesting movements (i.e., movements not related to breeding) during the normal breeding season in addition to the ranging within their home ranges: (i) long-distance directional movements (n = 3), (ii) intermediate-distance movements (n = 4), and (iii) movements within an unusually large home range (n = 1). These movements varied considerably, with some eagles travelling nearly 700 km north into northern Finland and Norway. No adults with transmitters reproduced successfully in 2012; in four territories, nests failed and in five territories occupied by pairs we did not know if eggs were laid. Post-nesting movements, which occurred after nesting or breeding failure, occurred in a year with apparently low food supply and may have been triggered by local food shortage.

During 2001, we used radiotelemetry to measure home range and habitat use of adult male Cooper's Hawks (Accipiter cooperii) in urban and natural areas in Orange County, California, USA. Breeding (n = 8) and non-breeding (n = 5) season home ranges and core areas were calculated via CALHOME using 95% and 50% adaptive kernel methods, respectively. We used a G-test of proportions to determine if Cooper's Hawks used the habitat types in their territories in proportion to their availability. We also recorded breeding success of hawks in natural and urban areas. Home ranges did not differ between urban and natural territories in the breeding season. In urban birds, there was a trend of larger territories in the breeding season compared to the non-breeding season. Cooper's Hawks nesting in natural areas used coast live oak and riparian habitat more often than expected, whereas Cooper's Hawks nesting in urban areas used parks/ornamental plantings and commercial/industrial areas more often than expected. Urban-nesting Cooper's Hawks successfully fledged an average of 3.75 +/- 0.5 young per nesting attempt, whereas natural-nesting Cooper's Hawks fledged an average of 1.5 +/- 1.9 young per nesting attempt. Our results contribute valuable information on home range and habitat use of urban-breeding Cooper's Hawks. Within urban home ranges this species prefers areas that mimic natural settings. Management for this species in urban areas should emphasize providing this sort of habitat.

We report the results of a 40-year study of the western Red-shouldered Hawk (Buteo lineatus elegans) involving the banding of 2742 nestlings in southern California from 1970 to 2009 (this study) plus 127 nestlings banded in other California studies (1956-2008) and the analyses of 119 records of subsequent recovery from the Bird Banding Laboratory (1957-2009). Of the Red-shouldered Hawks recovered, 109 (91.6%) moved <100 km (short-distance dispersers), while 10 (8.4%) moved >100 km (long-distance dispersers). Three (2.5%), all long-distance dispersers, were vagrants (recovered outside the species' range of residency), and were found 374 to 843 km northeast and south of their banding locations in the Mojave, Great Basin, and Vizcaino deserts. The distribution of directions of short-distance dispersal was bipolar, closely corresponding with the northwest southeast orientation of the species' range in southern California, while that of long-distance dispersers was mainly to the north. One of 10 long-distance dispersers, a nonvagrant, survived well into the age of breeding (103.0 months), whereas eight of the other nine perished before 14.5 months. The implications of vagrancy for conservation of this resident subspecies are that a relatively small source area can contribute genetic material over a vastly larger receiving area but rarely does so because of high mortality rates. Nonetheless, the movements of vagrants we documented provide evidence for the species' potential to populate new landscapes in response to changing environmental conditions and to maintain genetic heterogeneity within existing populations.