Do Golden Eagles Warrant Special Concern Based on Migration Counts in the Western United States? Reply to Mccaffery and Mcintyre

Abstract

In Hoffman and Smith (2003), we summarized two decades of raptor migration count data from western North America. McCaffery and McIntyre (2005) offer an extensive critique of the “conclusions” we drew from these data concerning the migration ecology and status of western Golden Eagles (Aquila chrysaetos). Many of their specific points about data limitations are well taken. Contrary to the flavor of their critique, however, we were not offering any definitive conclusions about the status or habits of eagles. Rather, we merely sought to describe the tendencies in the data and offer reasonable speculation about potential underlying causes of the documented patterns and trends. Our primary goal was to challenge colleagues to help us carefully consider our data and help formulate reasonable hypotheses about causal factors. We welcome and applaud McCaffery and McIntyre's (2005) thorough review of our work and genuine concern for guarding against unwarranted speculation. We believe, however that the depth of their critique was unjustified because the precision of the migration count data we presented simply is not sufficient to support detailed inspection of every annual change. Moreover, while we cannot disagree with them concerning the limits of the migration data we presented, we stand firmly behind our contention that there are indeed reasons to be concerned about the status of Golden Eagles in western North America, particularly within the sagebrush-steppe ecoregion. ¿Es el Estatus de Aquila chrysaetos Especialmente Preocupante de Acuerdo a los Conteos Migratorios del Oeste de los Estados Unidos?: Respuesta a McCaffery y McIntyre Resumen. En un trabajo previo (Hoffman and Smith 2003), resumimos datos sobre conteos de migración de rapaces realizados en el oeste de Norte América. McCaffery y McIntyre (2005) presentan una extensa crítica de las “conclusiones” que sacamos a partir de esos datos con respecto a la ecología de migración y el estatus de la especie Aquila chrysaetos. Muchos de sus argumentos específicos sobre las limitaciones de los datos son acertados. Sin embargo, en contraste con el tono de su crítica, en nuestro estudio no ofrecimos conclusiones definitivas sobre el estatus o los hábitos de A. chrysaetos. En cambio, simplemente quisimos describir las tendencias de los datos y presentar especulaciones razonables sobre las posibles causas de los patrones y tendencias documentados. Nuestro principal objetivo era desafiar a nuestros colegas para que nos ayudaran a considerar nuestros datos cuidadosamente y a formular hipótesis razonables sobre los factores causales. Por tanto, recibimos con beneplácito la revisión exhaustiva de nuestro trabajo hecha por McCaffery y McIntyre (2005) y su interés genuino en evitar especulaciones no fundamentadas. Sin embargo, creemos que la profundidad de su crítica no es justificable porque la precisión de los datos de los conteos de migración que presentamos es simplemente insuficiente para permitir la inspección detallada de todos los cambios anuales. Más aún, aunque no podemos estar en desacuerdo con ellos en cuanto a las limitaciones de los datos que presentamos, mantenemos firmemente nuestro argumento de que de hecho existen razones para estar preocupados por el estatus de A. chrysaetos en el oeste de Norte América, particularmente en la ecorregión de estepas y matorrales de Artemisia.

Estimating Natal Origins of Migratory Juvenile Golden Eagles Using Stable Hydrogen Isotopes

“…Analysis of long-term migration count data suggests a downward trend in observed numbers for this species. This has raised concern about the status of migratory Golden Eagles in western North America (Kochert and Steenhof 2002, Hoffman and Smith 2005, Smith et al 2008, Tilly 2008. However, interpreting migration count data can be difficult (McCaffery and McIntyre 2005) and requires knowledge of the source populations, which is incomplete for a majority of migration count sites (Hoffman and Smith 2003).…”

“…This has raised concern about the status of migratory Golden Eagles in western North America (Kochert and Steenhof 2002, Hoffman and Smith 2005, Smith et al 2008, Tilly 2008. However, interpreting migration count data can be difficult (McCaffery and McIntyre 2005) and requires knowledge of the source populations, which is incomplete for a majority of migration count sites (Hoffman and Smith 2003). By identifying the geographic origins of the avian migrants, it may be possible to relate migration count trends to a particular regional population of interest (Viverette et al 1996, Meehan et al 2001.…”

“…Recently, there has been a call for more information on Golden Eagles in the West (Pagel et al 2010). Downward trends in Golden Eagle numbers at migration count sites may be the result of factors on breeding or wintering grounds, or both, across western North America (Kochert and Steenhof 2002, Hoffman and Smith 2005, Smith et al 2008, Pagel et al 2010). However, one of the biggest obstacles in accurately interpreting raptor migration counts in relation to population status is determining origins and destinations of migrants, and this poses difficulties when addressing conservation issues and developing management strategies (Kochert andSteenhof 2002, Hoffman and.…”