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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 2. June 2012 
Yellowthroat by a casual observer. The singing 
female yellowthroat mentioned by Spector 
(1992) also sang a raspy, non-species typical 
song (B. E. Byers, pers. comm.). Additionally, 
all three sang during the pair formation stage of 
the breeding season and were not heard after 
nesting. Gilbert and Carroll (1999) suggest the 
atypical song they observed by a female Wilson’s 
Warbler (Cardellina pusilla) may have functioned 
during an extended period of pair bond formation 
and maintenance. Our female sang for only a few 
days, but the timing of singing suggests the 
behavior could have a similar function in pair 
bond formation in yellowthroats. 
The female that we observed appeared to be 
typical in all measured parameters except for 
singing. Our study provides no evidence that 
androgens, age, or breeding density had a role in 
inducing song. It is possible that song is functional 
in pair bond formation but it is apparently rarely 
used, as previous researchers have not reported it. 
Even if functional, it is unclear why this particular 
female sang when most females did not. Ulti¬ 
mately, die explanations available seem inade¬ 
quate and this female may have been anomalous 
in some dimension that we did not measure. 
ACKNOWLEDGMENTS 
We thank L. M. Duval and F,. A. Krasner for help with 
field observations and recordings, and W. M. Gilbert and an 
anonymous reviewer for comments that improved the 
manuscript. A National Science Foundation Graduate 
Research Fellowship to CCT supported this work. Research 
was conducted under Skidmore College Animal Care and 
Use Committee protocol #69 and the University of 
Califomia-Davis 1ACUC protocol #16362. 
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