Changes in heron and egret populations on the Laurentian Great Lakes and connecting channels, 1977-2009

Avian Conservation and Ecology

CynthiaPekarik,¹  D.V.Weseloh,¹  DavidMoore,¹  FrancescaCuthbert,²  LindaWires,²  Scott A Rush,³ 

[1] Canadian Wildlife Service;Department of Fisheries, Wildlife and Conservation Biology, University of Minnesota;Mississippi State University

关键词: Black-crowned Night-Heron;    Great Blue Heron;    Great Egret;    habitat succession;    isl;    s;    population trends;   

DOI  :  10.5751/ACE-00742-100107

学科分类：社会科学、人文和艺术（综合）

来源: Resilience Alliance Publications

【 摘 要 】

Canadian and U.S. federal wildlife agencies completed four decadal surveys, spanning the years 1977 to 2009, to census colonial waterbirds breeding on the Great Lakes and adjoining bodies of water. In this paper, we reports abundance, distribution, and general population trends of three species: Black-crowned Night-Heron (Nycticorax nycticorax), Great Egret (Ardea alba), and Great Blue Heron (Ardea herodias). Estimates of nest numbers ranged from approximately 4000-6100 for the Black-crowned Night-Heron, 250-1900 for the Great Egret, and 3800-6400 for the Great Blue Heron. Average annual rates of change in nest numbers between the first (1977) and fourth (2008) census were −1% for the Black-crowned Night-Heron, +23% for theGreat Egret, and −0.27% for the Great Blue Heron. Across the 30-year census, Black-crowned Night-Heron estimates decreased in U.S. (−57%) but increased (+18%) in Canadian waters, Great Egret nests increased 1381% in Canadian waters with a smaller, but still substantial increase in the number of nests at U.S. colonies (+613%), and Great Blue Heron numbers increased 148% in Canadian waters and 713% in U.S. waters. Although a single factor cannot be clearly linked to changes observed in each species’ distribution, hydrological variation, habitat succession, nest competition with Double-crested Cormorants (Phalacrocorax auritus), and land use changes likely all contributed. Management activities should support both breeding and foraging conditions including restoration of early successional habitats and anticipate continued northward expansions in the distributions of these waterbirds.

【 授权许可】

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