KLEPTOPARASITISM OF AMERICAN COOTS BY GADWALLS AND ITS RELATIONSHIP TO SOCIAL-DOMINANCE AND FOOD ABUNDANCE

Citation
Cr. Leschack et Gr. Hepp, KLEPTOPARASITISM OF AMERICAN COOTS BY GADWALLS AND ITS RELATIONSHIP TO SOCIAL-DOMINANCE AND FOOD ABUNDANCE, The Auk, 112(2), 1995, pp. 429-435
Citations number
33
Categorie Soggetti
Ornithology
Journal title
ISSN journal
00048038
Volume
112
Issue
2
Year of publication
1995
Pages
429 - 435
Database
ISI
SICI code
0004-8038(1995)112:2<429:KOACBG>2.0.ZU;2-J
Abstract
Kleptoparasitism of American Coots (Fulica americana) by Gadwalls (Ana s strepera) was recorded from October 1991-February 1992. We used thes e data to test whether frequency and rate of kleptoparasitism were rel ated to variation in food abundance and dominance status of Gadwalls. Overall, 30% (n = 423) of Gadwalls observed were kleptoparasitic; the relative frequency and rate of kleptoparasitism varied monthly. The pr oportion of individuals engaged in food stealing and the rate of klept oparasitism were greatest for subordinate sex/pair status classes of G adwalls. When comparing diurnal time-activity budgets, kleptoparasitic Gadwalls spent less time feeding (56 vs. 68%) and more time searching for food (37 vs. 24%) than did individuals not participating in klept oparasitism. Eurasian watermilfoil (Myriophyllum spicatum) was the pri mary food of Gadwalls and American Coots. As this aquatic macrophyte d eclined in abundance over the winter as a result of the effects of her bivory and natural senescence, so did numbers of coots and Gadwalls. W hen coot and Gadwall numbers were held constant statistically, the rat e of kleptoparasitism was inversely related to milfoil cover. Food-ste aling behavior of Gadwalls was influenced by social dominance and food abundance; it was mediated by host/parasite numbers. Results suggest that kleptoparasitism is an alternative foraging strategy used by subo rdinate Gadwalls that do not have access to good feeding areas.