Male and Female Reproductive Strategies in the Polygynous Bobolink

Most species of birds are socially monogamous, however approximately 8% of bird species are polygynous. By mating polygynously,females lose paternal care, but might gain access to a superior territory or male. We examined five factors that affect polygyny inbobolinks: territory size, perching sites, predation rate, insect abundance, and vegetation composition and structure. Our studysite was located in the Pend Oreille River Valley in northeast Washington State. Artificial perching sites were placed in the field,male territories were mapped, nests located and monitored, and vegetation assessed from May to mid-July 2003. Approximately55% of males were polygynous, and 45% were monogamous. Females arrived on the study site in three temporal waves that wecategorized as: first – monogamous, second – primary, and third – secondary females. Monogamous territories had higher caterpillardensities, higher herbaceous coverage, and were smaller in size than polygynous territories, reflecting the patchy vegetation ofthe study site.

Matthew P. Moskwik and Margaret A. O’Connell, Northwest Science, Vol. 80, No. 2, 2006