Survival Estimates and Cause of Mortality of Golden Eagles in South-Central Montana

Age‐specific survival rates, causes of death, and allowable take of golden eagles in the western United States

“…One concern with survival analyses based on transmitter‐tagged individuals is the possibility that transmitters negatively affect survival. Like Crandall et al (2019), we found no evidence of a negative effect on golden eagles with transmitters of the variable weights and shapes included in this study. Another potential source of bias is the destruction of transmitters by humans when eagles are illegally killed, but unlike studies of golden eagles in other countries (Whitfield & Fielding, 2017), the transmitter failure rates we observed were consistent with expected normal rates of failure in such devices.…”

“…The mean AY3 survival rate we estimated for golden eagles in the western United States is lower than that reported by other researchers working with this species in south-central Montana (0.93), roughly comparable to rates in west-central California (0.83-0.90, depending on breeding status), but slightly higher than that reported for southwestern Montana (0.86;Crandall et al, 2019, Harmata et al, 2018, Hunt et al, 2017; many of the eagles in these individual studies were also included in the present study). Fewer studies have reported comparable survival rates for other golden eagle age classes, but the rate we estimated for Y1 golden eagles is lower than that reported from west-central California (0.84) and the southern Colorado Plateau (0.79; Hunt et al, 2017;Murphy et al, 2017).…”

“…Humans caused nearly 60% of all golden eagle mortality in the coterminous western United States, and over 70% of AY1 mortality. High rates of anthropogenic mortality have been reported in most other studies of survival in this species (Crandall et al, 2019;Hunt et al, 2017;McIntyre, 2012;Whitfield & Fielding, 2017). In this study, however, we were able to quantitatively discriminate between the relative importance of anthropogenic and natural mortality factors at the population level.…”

“…Thus, differences between our results and others’ findings in local areas over shorter time periods are unsurprising. Undoubtedly, there are fine‐scale spatial and temporal differences in survival that reflect the relative preponderance of anthropogenic risks, the abundance of prey, the propensity to undertake long‐distance dispersal, and precipitation cycles that are smoothed over in our analysis (Hunt et al, 2017; Murphy et al, 2017; Crandall et al, 2019; Murphy et al, unpublished manuscript). Our objective in this analysis was to obtain estimates of survival representative of the study area as a whole and that incorporated all of the uncertainty associated with this variability, rather than to specifically model the local or regional variation in survival, because the U.S.…”

Conservation Letter: Lead Poisoning of Raptors

“…Golden Eagles (Aquila chrysaetos; least concern), a circumpolar apex predator, have documented lead exposure in the European Alps (Madry et al 2015), the United Kingdom (Pain et al 1995), and North America (Langner et al 2015). Lead poisoning is estimated to cause between 2.1% and 4.8% of Golden Eagle mortality in the USA (Russell and Franson 2014, US Fish and Wildlife Service 2016) but may be underestimated as a result of reporting bias (e.g., Crandall et al 2019).…”