Aberrant singing is associated with developmental stress and zero fitness in a male White-throated Sparrow ( Zonotrichia albicollis )

Oscine birdsong signals species identity, and individual quality, and functions as a cue for mate selection. Thus, producing an atypical song may have deleterious fitness effects. Nevertheless, learning during song development deems the vocal phenotype labile, creating the potential for errors, which may be elevated by developmental stress. Indeed, developmental stress has been shown to interfere with song learning in laboratory studies, but in the field, developmental conditions are rarely known, and knowledge of reproductive success is typically also lacking. We report on a male White-throated Sparrow (Zonotrichia albicollis) that we observed producing an atypical song comprised of a sparrow-like introductory phrase followed by a normal song. We banded this male as a nestling and observed potentially stressful developmental conditions that may have elevated the chances for learning errors. Specifically, this male hatched last in an asynchronous second clutch of three eggs, was structurally smaller than his siblings and fledged at nearly the latest date documented during that season. As an adult, he was unsuccessful at securing a social mate or extra-pair paternity, suggesting that females selected against his atypical vocal phenotype. Our observations of this unique individual support a connection between developmental stress, atypical song, and fitness outcomes.