Begging blue tit nestlings discriminate between the odour of familiar and unfamiliar conspecifics

Abstract

Summary Offspring often solicit, and compete for, limited parental care by elaborate begging behaviour. Kin selection theory predicts that competing offspring should modify the intensity of their begging depending on the degree of relatedness to their nest‐ or litter‐mates. Empirical evidence in birds, which are a key model in the study of parent‐offspring interactions, indeed indicates that a lower level of relatedness between offspring in the nest correlates with more intense begging (i.e. more ‘selfish’ behaviour). This implies that competing nestlings can recognize kin, but the mechanism underlying such discrimination is unclear. Birds have long been thought to mainly rely on visual and auditory cues in their social communication, but there is now growing evidence for the importance of olfactory cues too. To assess the potential importance of olfactory cues in modulating nestling begging behaviour, we experimentally tested in a free‐living bird, the blue tit Cyanistes caeruleus, if nestlings discriminate and adjust their begging behaviour depending on their familiarity with a conspecific nestling odour stimulus. We found that individuals responded with longer and more intense begging bouts to an unfamiliar compared with a familiar odour stimulus. Our findings provide first evidence for a role of olfaction in modulating offspring begging behaviour in a wild bird population. Although our experiment cannot differentiate between the effects of familiarity and relatedness, it raises the interesting possibility that blue tit nestlings may also discriminate between odours of close kin and less related individuals, and adjust their begging behaviour accordingly. This hypothesis requires further testing. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12886/suppinfo is available for this article.

Brood parasitism, relatedness and sociality: a kinship role in female reproductive tactics

“…Beecher, 1988;McDonald & Wright, 2011), and visual cues may also be involved (Palestis & Burger, 1999). Recognition may also be based on olfaction (Krause et al, 2012;Rossi et al, 2017). A study of cooperatively breeding long-tailed tits (Aegithalos caudatus) found that their behaviour was consistent with recognition learned by association, and that these birds can discriminate between kin and non-kin based on individual-specific characteristics of contact calls.…”

Nestling tree swallows (Tachycineta bicolor) alter begging behaviour in response to odour of familiar adults, but not their nests

“…For the nest scent recognition experiment, we tested nestlings at 1 day of age and found no difference in response between orange scent and water, whereas for the parent scent recognition experiment, we tested nestlings at 2 days of age and found a change in response depending on the scent type. Similar experiments on zebra finches performed on the day of hatch (Caspers et al, ) or 1 day after hatch (Caspers et al, ) found significant effects in response to odour type, while an experiment on blue tits, which also found significant effects in response to odour type, tested nestlings at 7 days post‐hatch (Rossi et al, ). As our experiment was the first such experiment on tree swallows, however, we cannot rule out that olfactory development may be slower in nestling tree swallows than zebra finches, and therefore, they may be more responsive to odour stimuli when they are older.…”

“…Cross‐fostering nestlings (Caspers & Krause, ) and eggs (Caspers, Hoffman, Kohlmeier, Krüger, & Krause, ) showed that nestlings learned the odour of their nest during a short time period around hatching. Nestling zebra finches also begged longer to odours of a familiar than unfamiliar adult (Caspers et al, ), whereas nestling blue tits ( Cyanistes caeruleus ) begged longer and more intensely to odours of unfamiliar than familiar nestlings (Rossi et al, ).…”

Conspecific olfactory preferences and interspecific divergence in odor cues in a chickadee hybrid zone

“…In several procellariform species, young chicks seem to demonstrate odor recognition (Cunningham, Buskirk, Bonadonna, Weimerskirch, & Nevitt, 2003;De Leon, Mínguez, & Belliure, 2003). Within the same family as chickadees (Paridae), blue tits have also been shown to exhibit odor recognition at the nestling stage (Rossi et al, 2017). Within the same family as chickadees (Paridae), blue tits have also been shown to exhibit odor recognition at the nestling stage (Rossi et al, 2017).…”

“…Preference for extraneous odors has been found to develop during the incubation period in chickens (Sneddon, Hadden, & Hepper, 1998) while preferences for parental odors may be determined earlier in egg development in zebra finches . Within the same family as chickadees (Paridae), blue tits have also been shown to exhibit odor recognition at the nestling stage (Rossi et al, 2017). While more work needs to be done in this area, the possibility that odor preferences are formed during development in chickadees could facilitate its function in reproductive isolation if individuals learn preferences from parental odors in pure-species nests.…”