Frequency and Distribution of Polygyny in Great Lakes Herring Gulls in 1978

Polygynous mating in Herring Gulls has been found only in northern Great Lakes breeding colonies. In 1978, I censused 21 colonies in northern Lake Michigan and Lake Huron to provide a baseline from which to gauge any future changes in the distribution and frequency of polygyny. Among 10,740 nests, I found 33 (0.3%) double-nests. Double-nests are two contiguous nest cups that contain eggs and are attended by one male and two females. I also found 30 (0.3%) nests with more than four eggs. These nests usually are attended by only two females (female associations). Polygynous groups and female associations were concentrated in northeastern Lake Michigan. The simultaneous occurrence of polygyny and female associations in Great Lakes Herring Gulls differs from the situation in other gull species in which only female associations have been described.