Causes of mortality in eagles submitted to the National Wildlife Health Center 1975-2013

Abstract

We summarized the cause of death for 2,980 bald eagles (Haliaeetus leucocephalus) and 1,427 golden eagles (Aquila chrysaetos) submitted to the National Wildlife Health Center in Madison, Wisconsin, USA, for diagnosis between 1975 and the beginning of 2013. We compared the proportion of eagles with a primary diagnosis as electrocuted, emaciated, traumatized, shot or trapped, diseased, poisoned, other, and undetermined among the 4 migratory bird flyways of the United States (Atlantic, Mississippi, Central, and Pacific). Additionally, we compared the proportion of lead-poisoned bald eagles submitted before and after the autumn 1991 ban on lead shot for waterfowl hunting. Trauma and poisonings (including lead poisoning) were the leading causes of death for bald eagles throughout the study period, and a greater proportion of bald eagles versus golden eagles were diagnosed as poisoned. For golden eagles, the major causes of mortality were trauma and electrocution. The proportion of lead poisoning diagnoses for bald eagles submitted to the National Wildlife Health Center displayed a statistically significant increase in all flyways after the autumn 1991 ban on the use of lead shot for waterfowl hunting. Thus, lead poisoning was a significant cause of mortality in our necropsied eagles, suggesting a continued need to evaluate the trade-offs of lead ammunition for use on game other than waterfowl versus the impacts of lead on wildlife populations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Lead and eagles: demographic and pathological characteristics of poisoning, and exposure levels associated with other causes of mortality

“…As a proportion of the total number of bald eagles examined at the NWHC, the frequency of those diagnosed with lead poisoning increased in the U.S. after implementation of the 1991 restrictions on hunting waterfowl with lead shot (Russell and Franson 2014). The largest increase, from 6 % before 1991 to 30 % after 1991 occurred in the Pacific flyway (Russell and Franson 2014). No increase in lead poisoning was detected in golden eagles, but the sample size for that species was much smaller (Russell and Franson 2014).…”

“…In that report, lead toxicosis was the most frequently diagnosed poisoning in both species, comprising 63.5 % of all poisonings in bald eagles and 58.1 % in golden eagles. As a proportion of the total number of bald eagles examined at the NWHC, the frequency of those diagnosed with lead poisoning increased in the U.S. after implementation of the 1991 restrictions on hunting waterfowl with lead shot (Russell and Franson 2014). The largest increase, from 6 % before 1991 to 30 % after 1991 occurred in the Pacific flyway (Russell and Franson 2014).…”

“…A retrospective summary of causes of mortality in more than 4,400 bald eagles and golden eagles submitted to the National Wildlife Health Center (NWHC) from throughout the U.S. during 1975-2013 identified the same top four causes of death, although not in the same order, for both species: poisoning, trauma, electrocution, and shooting (Russell and Franson 2014). In that report, lead toxicosis was the most frequently diagnosed poisoning in both species, comprising 63.5 % of all poisonings in bald eagles and 58.1 % in golden eagles.…”

Mortality Patterns in Endangered Hawaiian Geese (Nene; Branta Sandvicensis)

“…Passive surveillance strategies such as those used here have limitations, particularly when interpreting temporal trends when efforts to detect specimens are poorly documented or diagnostic effort is inconsistent (Russel and Franson 2014). In our case, animals were consistently examined by the same group by using similar techniques throughout the study, which should decrease variability.…”

Identifying Bald Versus Golden Eagle Bones: A Primer for Wildlife Biologists and Law Enforcement Officers

“…Most recorded deaths are anthropogenic, including shooting, electrocution, and lead poisoning (Russell and Franson 2014;USFWS 2016a). Recent reviews concluded that U.S. golden eagle populations are either stable or slowly declining (USFWS 2016a).…”