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J Wildl Dis. 2017 Oct;53(4):816-823. doi: 10.7589/2017-02-027. Epub 2017 Jul 28.

INFLUENCE OF SNOWFALL ON BLOOD LEAD LEVELS OF FREE-FLYING BALD EAGLES (HALIAEETUS LEUCOCEPHALUS) IN THE UPPER MISSISSIPPI RIVER VALLEY.

Author information

1
1   Department of Biology, Bruner Hall of Science, University of Nebraska at Kearney, 2401 11th Avenue, Kearney, Nebraska 68849, USA.
2
2   Northeast Iowa Community College, 8342 NICC Drive, Peosta, Iowa 52068, USA.
3
3   Eagle Valley, 8411 Duncan Road, Glen Haven, Wisconsin 53810, USA.
4
4   The Raptor Center, University of Minnesota, 1920 Fitch Avenue, St. Paul, Minnesota 55180, USA.
5
5   Minnesota Department of Natural Resources, 23070 N Lakeshore Drive, Glenwood, Minnesota 56334, USA.

Abstract

Lead poisoning of scavenging raptors occurs primarily via consumption of game animal carcasses containing lead, which peaks during fall firearm hunting seasons. We hypothesized that snowfall would mitigate exposure by concealing carcasses. We categorized blood lead level (BLL) for a subsample of Bald Eagles (Haliaeetus leucocephalus) from the Upper Mississippi River Valley and described BLL with respect to age, sex, and snowfall. We captured Bald Eagles overwintering in the Upper Mississippi River Valley (n=55) between December 1999 and January 2002. Individual BLL ranged from nondetectable to 335 μg/dL, with 73% of the samples testing positive for acute exposure to lead. Eagle BLL did not significantly differ between age or sex, but levels were higher immediately following the hunting season, and they were lower when the previous month's snowfall was greater than 11 cm. This study suggests a window of time between the white-tailed deer (Odocoileus virginianus) hunting season and the onset of snow when the population experienced peak exposure to lead. Combining these findings with existing research, we offer a narrative of the annual lead exposure cycle of Upper Mississippi River Valley Bald Eagles. These temporal associations are necessary considerations for accurate collection and interpretation of BLL.

KEYWORDS:

Ammunition; Bald Eagle; Haliaeetus leucocephalus; Mississippi River; blood; hunting; lead; snowfall

PMID:
28753412
DOI:
10.7589/2017-02-027
[Indexed for MEDLINE]

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