Pairing and nest site selection in solitary and yellow-throated vireos with a description of a ritualized nest building display

Abstract

Solitary (Vireo solitarius) and yellow-throated (Vireo flavifrons) vireos were studied in May and June, in Ontario between 1969 and 1975, and in British Columbia in 1976. Most unmated males search for nest sites and begin to build nests prior to the arrival of females in their territories. Upon the female's arrival, the first displays by the male are precopulatory. Displays involving chasing are seldom seen. Nests started by males, and other suitable nest sites serve as display areas during pair formation. The presence of more than one display site indicates that nests started by males are more important in pairing than as sites for final nests. A nest building display occurs most often and vigorously in the early building period when the male is actively assisting in nest construction. The frequency and duration of the display then wanes along with the male's building activity. The nest building display is not part of the precopulatory display, but has become important in pair formation. The males appear to choose the site for a final nest.