In colonially breeding birds, the need to discriminate between individuals is essential; hence strong selection for recognition systems is expected. Especially so in the context of parent/offspring communication during post-fledging parental care where parents have to recognize and find their own chicks in the breeding colony among other unrelated chicks. It is widely known that food-provisioning parents and fledglings of many bird species use acoustic signals to reveal their identity. However, these contact or begging calls are additionally important as dynamic, hunger-related signals of need in young birds. Here we are investigating how dynamic signals of need can additionally act as reliable indicators of a chick’s identity in the colonially breeding Golden-backed Weaver (Ploceus jacksoni). In a field study we experimentally manipulated the hunger level of chicks close to fledging and investigated the effects on variation in acoustic begging call parameters. Most call parameters, like amplitude, call length or mean call frequency changed with hunger level. In contrast, frequency modulation, an often cited acoustic parameter important for individual recognition, was unaffected by a chick’s state of hunger. Most interestingly, our results indicate that even highly dynamic signals of need can act as reliable indicators of a chick’s identity, due to large between –individual differences in these traits. These findings indicate that individual recognition processes are not necessarily based on static acoustic traits only but may additionally incorporate dynamic call characteristics.
Acoustic signalling of hunger and identity in colonial weaver bird chicks [abstract]
(2012).
Acoustic signalling of hunger and identity in colonial weaver bird chicks [abstract]. Bioacoustics,
Volume 21
(1):
51
Abstract: