NOTES ON SOME MARSH BIRDS OF CAPE SAN ANTONIO, ARGENTINA *

Summary During an 11‐month study of the Black‐headed Duck in eastern Argentina, observations were made on the marsh birds of Cape San Antonio, Province of Buenos Aires. These observations supplement the distributional and life history obtained by Gibson (1879–1920), Wetmore (1926) and others. The deep, fresh‐water marshes characteristically are dominated by one of three plants: tules, cutgrass or cat‐tails. There were surprisingly few marshes with mixtures of these plants and few marshes which showed a gradual transition from marsh to uplands. Marsh birds showed considerable adaptation in chronology of nesting and nest‐site selection for the seasonal water cycle of wet springs and dry periods in the late summer and fall. Some marsh birds were involved in nesting over a longer period than is usual in Northern Hemisphere marshes. As seems characteristic of all marsh birds, cover‐water edges were usual sites for nests. There were only a few species with restricted nest‐site selection, and competition between closely related species was noted only among the three species of coots. A list of the marsh birds of the area is given, and comments are presented on the ecology and behaviour of selected species.