Acoustic parameters of begging calls indicate chick body condition in Wilson’s storm-petrels Oceanites oceanicus

Abstract

Begging behaviour as a key element in the parent-offspring conflict has been studied in many avian species. These types of studies have nearly exclusively been based on call counts, and it is still not entirely clear whether begging calls themselves contain any information. We studied begging behaviour in Wilson's storm-petrel Oceanites oceanicus, a small procellariiform seabird. This species provides the opportunity to study the signalling value of begging calls in the absence of potentially confounding factors such as nestling competition, previous feeding experiences and predation pressure. We applied a new method using a semi-automatic spectrogram analysis software that measures the acoustic parameters of begging calls. Our analysis revealed that the frequency parameters of begging calls reflect chicks' current body condition, with chicks in poorer condition uttering calls at higher frequencies. Chicks uttering higher pitched calls also received larger meals. Our study shows that certain acoustic parameters of begging calls can indicate the state of a chick in Wilson's storm-petrels.

Functional characterization of begging calls in Thin-billed Prions <I>Pachyptila belcheri</I> chicks

“…While some previous studies have found acoustical parameters of begging call elements to be important in parent-chick interactions (Barn Swallows: Sacchi et al 2002), or to contain at least additional information (Wilson's Storm-Petrels: Gladbach et al 2009), another study did not find evidence that acoustic features of call elements are involved in the information exchange (Cory's Shearwaters: Träger et al 2006). In the latter study, no acoustic features of call elements correlated with body condition.…”

“…% observations % calls in 1st session changes in acoustic begging call parameters (Gladbach et al 2009), suggesting a minor importance of this component of the begging signal.…”

“…Another advantage is that there is no size difference between male and female chicks, and hence that there is no difference in nutritional requirements between sexes. In several procellariiform species, parents were found to respond to chicks' begging signals and meet the individual demands of their offspring, if the environmental context allowed it: Manx Shearwaters Puffinus puffinus , Hamer et al 2006), Cory's Shearwater Calonectris diomedea (Granadeiro et al 2000, Träger et al 2006, Quillfeldt et al 2007d) and Wilson's Storm-Petrel Oceanites oceanicus (Quillfeldt 2002, Gladbach et al 2009). While these previous studied were mostly based on the analysis of call rates and numbers, two studies also included acoustical parameters of begging call elements.…”

“…The results from these two studies were in part contradictory. While the begging calls of Cory's Shearwaters did not contain information on body condition (Träger et al 2006), Wilson's Storm-Petrels chicks increased the acoustical frequency of their calls when they were hungrier (Gladbach et al 2009). As the effect size in the latter study was small, this raises the possibility that there may be little causal relationship between a chick's nutritional requirements and the acoustical parameters of its begging calls.…”

“…Since both the rate and number of calls can only be assessed over time, it has been suggested that particular features of single begging elements could convey much more rapid information about the chick's body condition (Sacchi et al 2002, Gladbach et al 2009). This hypothesis has seldom been tested but has received experimental support for a multiparous species, the Barn Swallow Hirundo rustica (Sacchi et al 2002).…”