Coordination of care by breeders and helpers in the cooperatively breeding long-tailed tit

Abstract

In species with biparental and cooperative brood care, multiple carers cooperate by contributing costly investments to raise a shared brood. However, shared benefits and individual costs also give rise to conflict among carers conflict among carers over investment. Coordination of provisioning visits has been hypothesized to facilitate the resolution of this conflict, preventing exploitation, and ensuring collective investment in the shared brood. We used a 26-year study of long-tailed tits, Aegithalos caudatus, a facultative cooperative breeder, to investigate whether care by parents and helpers is coordinated, whether there are consistent differences in coordination between individuals and reproductive roles, and whether coordination varies with helper relatedness to breeders. Coordination takes the form of turn-taking (alternation) or feeding within a short time interval of another carer (synchrony), and both behaviors were observed to occur more than expected by chance, that is, “active” coordination. First, we found that active alternation decreased with group size, whereas active synchrony occurred at all group sizes. Second, we show that alternation was repeatable between observations at the same nest, whereas synchrony was repeatable between observations of the same individual. Active synchrony varied with reproductive status, with helpers synchronizing visits more than breeders, although active alternation did not vary with reproductive status. Finally, we found no significant effect of relatedness on either alternation or synchrony exhibited by helpers. In conclusion, we demonstrate active coordination of provisioning by carers and conclude that coordination is a socially plastic behavior depending on reproductive status and the number of carers raising the brood.

Fitness benefits of alternated chick provisioning in cooperatively breeding carrion crows

“…On current evidence, turn‐taking seems common in birds (e.g. Halliwell et al., 2022; Johnstone et al., 2014; Koenig & Walters, 2016; Savage et al., 2017; but see Khwaja et al., 2017) and may therefore afford fitness benefits in many species, including both biparental and cooperative breeding systems. Future research on environmental (e.g.…”

“…Indeed, birds usually need to forage away from the nest before coming back to feed the brood, making alternated visits by different carers more likely than consecutive visits of the same individual ('passive turn-taking'; Savage et al, 2017). The few relevant studies currently available confirmed that alternation can occur in groups with more than two carers (Halliwell et al, 2022;Koenig & Walters, 2016;Savage et al, 2017), supporting the view that cooperative care results from individuals responding to the investment of others and adjusting their own behaviour accordingly. An interesting exception is that of the rifleman Acanthisitta chloris, where carers do not coordinate, possibly because of the low level of potential conflict over nestling care in this species (Khwaja et al, 2017).…”