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Scale-dependent habitat selection of nesting Great Egrets and Snowy Egrets

Waterbirds

By:
, ,
DOI: 10.1675/1524-4695(2007)030[0384:SHSONG]2.0.CO;2

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Abstract

Foraging habitat selection of nesting Great Egrets (Ardea alba) and Snowy Egrets (Egretta thula) was investigated within an estuary with extensive impounded salt marsh habitat. Using a geographic information system, available habitat was partitioned into concentric bands at five, ten, and 15 km radius from nesting colonies to assess the relative effects of habitat composition and distance on habitat selection. Snowy Egrets were more likely than Great Egrets to depart colonies and travel to foraging sites in groups, but both species usually arrived at sites that were occupied by other wading birds. Mean flight distances were 6.2 km (SE = 0.4, N = 28, range 1.8-10.7 km) for Great Egrets and 4.7 km (SE = 0.48, N = 31, range 0.7-12.5 km) for Snowy Egrets. At the broadest spatial scale both species used impounded (mostly salt marsh) and estuarine edge habitat more than expected based on availability while avoiding unimpounded (mostly fresh water wetland) habitat. At more local scales habitat use matched availability. Interpretation of habitat preference differed with the types of habitat that were included and the maximum distance that habitat was considered available. These results illustrate that caution is needed when interpreting the results of habitat preference studies when individuals are constrained in their choice of habitats, such as for central place foragers.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Scale-dependent habitat selection of nesting Great Egrets and Snowy Egrets
Series title:
Waterbirds
DOI:
10.1675/1524-4695(2007)030[0384:SHSONG]2.0.CO;2
Volume
30
Issue:
3
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Waterbirds
First page:
384
Last page:
393
Number of Pages:
10