The Journal of Neuroscience, January 1, 1999, 19(1):476-483
Contributions of Social Cues and Photoperiod to Seasonal
Plasticity in the Adult Avian Song Control System
Anthony D.
Tramontin1,
John C.
Wingfield1, and
Eliot A.
Brenowitz1, 2
Departments of 1 Zoology, and 2 Psychology,
University of Washington, Seattle, Washington 98195
In seasonally breeding birds, the vernal growth of the song system
is thought to result primarily from increased daylength and the
associated increase in circulating testosterone. Other environmental
factors such as social cues between mates influence the timing of
reproduction, but less is known about how social cues might affect the
song system and song behavior. We used white-crowned sparrows
(Zonotrichia leucophrys gambelii) to test the hypothesis that the presence of a female in breeding condition influences song
nuclei and song behavior of adult males. There were four treatment
groups: (1) eight males housed individually in the same room on long
days and paired with estradiol-implanted females; (2) eight males
housed similarly on long days but without females; (3) four males
isolated on long days; and (4) four males isolated on short days. The
volumes of two song nuclei, HVc and RA, were significantly larger in
males housed with females than in any other treatment group. Males
isolated on short days had smaller HVc, RA, and area X volumes than all
other groups. The volumes of Rt (a thalamic nucleus not involved in
song) and the telencephalon did not differ among groups. Plasma
androgen levels did not differ among the three long-day, social
treatment groups at the times sampled, but were lower in the short-day
isolates. Males paired with females sang at a higher maximum rate than
males housed together, who sang at a higher rate than long-day
isolates. These results suggest that seasonal plasticity in the adult
song system is influenced by social cues.
Key words:
bird; bird song; communication; social influences; song
system; song nuclei; white-crowned sparrow
Copyright © 1999 Society for Neuroscience 0270-6474/99/191476-08$05.00/0