Nestling Begging Call Structure and Bout Variation Honestly Signal Need but Not Condition in Spanish Sparrows

Paulo A. M. Marques, Luis Vicente, and Rafael Marquez (2009) Nestling begging call structure and bout variation honestly signal need but not condition in Spanish Sparrows. Zoological Studies 48(5): 587-595. Nestling begging behavior in the context of parent-offspring communication has long been seen as a signal by which nestlings solicit care. Begging is a multi-component signal in which both acoustic and visual components are usually important; however, the present knowledge about the specific behavioral features that convey the information is still poor. The aim of this study was to examine how information on nestling's need is encoded in the begging calls given by nestling Spanish Sparrows (Passer hispaniolensis). Nestlings were individually submitted to a food-deprivation period and stimulated to beg at regular intervals within that period, and their acoustic reactions were studied. Spanish Sparrow nestlings increased their response to simulated parental visits in reaction to increasing food-deprivation periods. Results also confirmed that information on nestling need might be encoded in variables of calling behavior. The variables important to convey such information are the initial call rate (20 s rate), duration of the begging bout, call amplitude, and call high frequency. As food-deprivation periods increased, nestlings begged more frequently, extended the calling bout, increased the call amplitude, and used higher frequencies. During the deprivation period, nestlings did not change their call latency, call duration, or relative peak time. The study also found that despite expectations, lower-condition nestlings did not beg more frequently during the experiment than their higher-condition siblings. Overall, results support the view of begging as a reliable signal, namely that begging should reflect a nestling's need, and that only some call features might encode information about need. http://zoolstud.sinica.edu.tw/Journals/48.5/587.pdf