Nestling use of alternative acoustic antipredator responses is related to immune condition and social context

• Published in: Animal behaviour Vol. 91; pp. 161 - 169
• Main Authors: Goedert, Debora, Dias, Raphael I., Macedo, Regina H.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.05.2014; Harcourt Brace Jovanovich Ltd
• Subjects: acoustic signalling; Acoustics; Animal behavior; Animal communication; antipredator call; Birds; campo flicker; Colaptes; Colaptes campestris campestris; distress call; honest signal; Immunology; Ornithology; Picidae; Predation; Colaptes campestris campestris; acoustic signalling; Picidae; honest signal; campo flicker; antipredator call; distress call
• ISSN: 0003-3472; 1095-8282
• DOI: 10.1016/j.anbehav.2014.03.012

Birds present a variety of antipredator responses, including the use of acoustic signals that may be directed to other individuals or to the predator. We tested competing hypotheses regarding antipredator responses by analysing patterns of variation in the use of distress calls in campo flicker, Colaptes campestris campestris, nestlings. More specifically, we tested whether immune response and social context (presence or absence of other individuals of the social group) were associated with variation in use of acoustic signals in response to human handling. Individuals with higher immunocompetence used proportionally more harsh, low-pitched calls (‘scream’ notes) than individuals with lower immunocompetence, while the latter used mostly tonal, high-pitched calls (‘week’ notes); in both cases there was no influence of the social context on call type. Individuals responded to the social context by giving fewer scream notes and week notes in the presence of adults of the social group than when the adults were absent. Although playbacks are necessary to determine the function of the calls, our results indicate that campo flicker nestling antipredator calls could be used to attract other individuals of the group to help defend the nestling. Also, the use of proportionally more scream notes by healthier individuals suggests that these notes could act as an honest signal of the nestlings' physiological condition. •Flexibility in use of signals can provide cues about the function of these signals.•Calls of campo flicker nestlings appear to be directed to conspecifics, as ‘call-for-help’ signals.•‘Scream’ calls could also attract secondary predators.•The type of call used seems to be an honest indicator of nestling condition.•Individuals in poor condition seem to give ‘week’ calls as the ‘best-of-a-bad-job’.