Summary
We removed the mates of ten male blackcapped chickadees (Parus atricapillus) during the nestbuilding period to determine the effect of female presence on dawn singing. During the first dawn chorus following mate removal, males sang significantly longer, increased movement within their territory, and increased the percentage of their territory covered while singing. After the female was returned, these parameters returned to the pre-removal values. Males did not alter the frequency range or modal frequency of their songs when the mate was removed, nor did they change the degree of frequency shifting in the fee-bee song. We conclude that dawn singing in the black-capped chickadee acts, in part, as an intersexual signal, and that the behavior of frequency shifting in the song may be directed more toward rival males than females.
Methodology
We recorded dawn singing in ten territorial male black-capped chickadees from a color marked population at the Queen's University Biological Station (45 ° N, 76 ° W) during the nest-building, pre-incubation period (20 Apri-13 May 1992). We mapped the territories and determined the mating status of the males prior to recording. We visited each subject's territory before dawn and recorded the entire chorus. A chorus was deemed to have ended when the focal bird stopped singing for more than 5 min, while simultaneously engaging in a secondary activity (usually foraging).