Patterned daytime singing of the eastern wood-pewee, Contopus virens

Abstract

The daytime singing of male eastern wood-pewees, Tyrannidae: Contopus virens, is based on two distinctive song forms, organized in conspicuously non-random sequences. The sequencing grammar dictates that single utterances of the rarer song should separate strings of the other form. The strings provide an efficient way of revealing current proportions of the two song forms over periods as short as a few seconds or as long as tens of seconds. As the number of songs changes among successive strings, so too does the probability of the singer flying. Further, with their shortest strings, singers actively promote opportunities for interactions, for instance by approaching or staying near other birds or special places. As singers utter the more common song form in increasingly longer strings their activities promoting interactions decline rapidly, their receptivity to interactional overtures by other individuals declines, although much less rapidly, and the extent to which they are occupied with non-interactional behaviour increases. The correlations of string lengths with flight may be an epiphenomenon. The remaining correlations, however, are likely to be important to listening pewees as they assess the ways in which a singer may engage in social behaviour.