Distress calls may honestly signal bird quality to predators

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 271; no. Suppl 6; pp. S513 - S515
• Main Authors: Laiolo, Paola, Tella, José L., Carrete, Martina, Serrano, David, López, Guillermo
• Format: Journal Article
• Language: English
• Published: England The Royal Society 07-12-2004
• Subjects: Analysis of Variance; Animal vocalization; Animals; Atlantic Islands; Bird calls; Bird songs; Birds; Body Condition; Body Constitution - physiology; Body Weight; Body Weights and Measures; Calandrella rufescens; Distress Calls; Frequency ranges; Health status; Honest Signal; Immune response; Immunocompetence; Immunocompetence - physiology; Passeriformes - immunology; Passeriformes - physiology; Phytohemagglutinins; Predators; Predatory Behavior; Prey Quality; Principal Component Analysis; Principal components analysis; Selection, Genetic; Sound Spectrography; Tape Recording; Vocalization, Animal - physiology; Atlantic Islands
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rsbl.2004.0239

In predator-prey interactions, both interactors may benefit from sharing information about prey vulnerability. We examined the relationship between calls used to discourage close predators (distress calls) and the health condition of the caller to test whether these signals are reliable indicators of prey quality. The structure of calls from captured lesser short-toed larks Calandrella rufescens was related to their body condition and T-cell-mediated immunocompetence. Birds in better nutritional and immunological condition utter harsher calls (i.e. they spread the call energy over a wider range of frequency) than birds in poorer conditions. Hence, the harshness of distress calls seems honestly to signal the health status of prey and thus their ability to escape, on which the predator might base its optimal foraging choice. Previous studies have investigated the honesty of songs that have evolved via sexual selection, but this is the first study, to our knowledge, the demonstrates a relationship between individual quality and a vocalization primarily shaped by natural selection.