ECOMORPHOLOGICAL RELATIONSHIPS AMONG PALEARCTIC DABBLING DUCKS ON BALTIC COASTAL WETLANDS AND A COMPARISON WITH THE NEARCTIC

We examined patterns of (1) microhabitat niche relationships among coe xisting dabbling ducks and (2) feeding morphology in relation to micro habitat structure on coastal wetlands in southern Gotland. Sweden. and compared these results to those of an assemblage of matched species i n the Nearctic. Thirteen microhabitat variables were reduced to 2 prin cipal components; one reflected variation in the height and density of emergent vegetation from inshore to offshore sites, the other, the de gree of vegetation-water interspersion. Over all wetlands. and on indi vidual wetlands, species separated most on the vegetation interspersio n gradient, although the inshore-offshore vegetation gradient also con tributed significantly to species' separation. Microhabitat separation tended to be inversely correlated with species richness, and species richness did not vary with wetland size (and index of within-wetland m icrohabitat diversity). Species with fine lamellar density tended to f orage in open, offshore microhabitats and species with coarse density tended to forage in vegetated. inshore sites. This pattern mirrors tha t found across North America, where it may be explained by the size di stribution of invertebrate prey.