Song variation in a population of chestnut-sided warblers (Dendroica pensylvanica): its nature and suggested significance

Abstract

Song variation in a population of chestnut-sided warblers (Dendroica pensylvanica) was investigated during 1970–1972 in Hillsboro County, New Hampshire. Five song types, which appear to be shared by all males in the local population, are described and are used differentially by the birds. Two 'accented ending' song types are used primarily by undisturbed males located centrally on their territories. Two 'unaccented ending' song types are used in territorial encounters, or when a male is located peripherally on his territory. The fifth type, 'jumbled song,' is used almost exclusively during territorial encounters. There is no evidence of special association of any of the types with male–female interactions. It is suggested that the song types form a graded series of signals, increasing the efficiency of male–male communication by transmitting more precise messages than would be possible with only a single song type.