Comparison of two foraging habitats used by glossy ibis during the breeding season in Rhode Island

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In 2002, an estimated 377 pairs of Plegadis falcinellus (Glossy Ibis) nested in four mixed-species colonies in Rhode Island, with 66% of nests on Rose Island. Local observations suggest that farmland may provide important foraging habitat for Glossy Ibis in southern New England. We systematically surveyed 13 salt marshes within 20 km and 11 farms within 10 km of Rose Island during the breeding season (15 May-23 July) in 2002 to determine the importance of salt marshes and farmland to foraging Glossy Ibis. Foraging ibis were irregularly detected at 6 of 13 salt marshes. Ibis were more likely to be observed foraging at farms, with an average of 1 to 18 birds seen at 10 of 11 farms. Linear models of habitat characteristics predicting the mean number of foraging ibis observed at each farm were created a priori and evaluated using Akaike's Information Criteria. Farms with a high density of cows present (> 10 cows per ha) and farms that contained streams were especially important, but foraging ibis used many agricultural habitat types including cultivated grass, wet areas, uncut meadows, and recently mowed hayfields. This study clearly shows that active farms are beneficial to breeding Glossy Ibis in Rhode Island and that efforts to preserve such farms will help to sustain the ibis population in the region.

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Northeastern Naturalist