title: Wintering Bald Eagle Count Trends in the Conterminous United States, 1986-2010.
abstract: We analyzed counts from the annual Midwinter Bald Eagle Survey to examine state, regional, and national trends in counts of wintering Bald Eagles (Haliaeetusleucocephalus) within the conterminous 48 United States from 1986 to 2010. Using hierarchical mixed model methods, we report trends in counts from 11,729 surveys along 844 routes in 44 states. Nationwide Bald Eagle counts increased 0.6% per yr over the 25-yr period, compared to an estimate of 1.9% per yr from 1986 to 2000. Trend estimates for Bald Eagles were significant (P≤0.05) and positive in the northeastern and northwestern U.S. (3.9% and 1.1%, respectively), while trend estimates for Bald Eagles were negative (P≤0.05) in the southwestern U.S. (-2.2%). After accounting for potential biases resulting from temporal and regional differences in surveys, we believe trends reflect post-DDT recovery and subsequent early effects of density-dependent population regulation.
authors.affiliation: U.S. Army Corps of Engineers, South Pacific Division, 1455 Market Street, San Francisco, CA 94103 U.S.A.
authors.forename: Wade L
authors.initials: WL
authors.lastname: Eakle
authors.affiliation: Boise State University, Biomolecular Research Center, Boise, ID 83725 U.S.A.
authors.forename: Laura
authors.initials: L
authors.lastname: Bond
authors.affiliation: U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 970 Lusk Street, Boise, ID 83706 U.S.ABoise State University Raptor Research Center, Boise, ID 83725 U.S.A.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Fuller
authors.affiliation: U.S. Army Engineer Research and Development Center, Environmental Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180 U.S.A.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Fischer
authors.affiliation: Owyhee Desert Studies, 18109 Briar Creek Road, Murphy, ID 83650 U.S.A.
authors.forename: Karen
authors.initials: K
authors.lastname: Steenhof
keywords: Bald Eagle; Haliaeetus leucocephalus; U.S.A.; climate change; contiguous 48 states; population trends; survey; wintering