Interspecific Density Influences the Adaptive Significance of Provisioning Coordination Between Breeding Partners

When two or more individuals cooperate to provision a shared brood, each carer may be able to maximize their payoffs by coordinating provisioning in relation to what others are doing. This investment “game” is not simply a matter of how much to invest but also of the relative timing of investment. Recent studies propose that temporal coordination of care in the forms of alternation (i.e., turn-taking) and synchrony (i.e., provisioning together) function to mitigate conflict between carers and reduce brood predation risk, respectively. Such coordination is widespread in biparental and cooperatively breeding birds, yet the fitness consequences have rarely been empirically tested. Here, we use a long-term study of long-tailed tits Aegithalos caudatus, a facultative cooperatively breeding bird with active coordination of care, to assess the support for these hypothesized functions for coordination of provisioning visits. First, we found evidence that turn-taking mitigates conflict between carers because, in cooperative groups, provisioning rates and offspring recruitment increased with the level of active alternation exhibited by carers and with the associated increase in provisioning rate parity between carers. In contrast, offspring recruitment did not increase with alternation in biparental nests, although it was positively correlated with parity of provisioning between carers, which is predicted to result from conflict mitigation. Second, synchronous nest visits were associated with a reduced probability of nest predation and thus increased brood survival, especially when provisioning rates were high. We attribute this effect to synchrony reducing carer activity near the nest. We conclude that temporal coordination of provisioning visits in the forms of alternation and synchrony both confer fitness benefits on carers and despite being intrinsically linked, these different kinds of coordination appear to serve different functions.

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Competitive events during nest‐building influence offspring growth and behaviour, but not testosterone deposition in the egg yolk in Western Bluebirds (Sialia mexicana)

Hernández

Hernandez-Martínez

Nicolás

et al. 2022

Ibis

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The environmental stressors that females face before egg‐laying, such as competition for resources, can impact the fitness prospects of the female as well as her offspring through hormone‐mediated maternal effects. In obligate secondary cavity‐nesting species, suitable nest‐holes are a limited resource, so gaining access to nest‐sites may require competition with other individuals. In the Western Bluebird Sialia mexicana, we experimentally evaluated whether female exposure to increased competition for nest cavities (reduced available nest‐holes plus exposure to a competitor's decoy and vocalizations) during the period of nest construction affects her offspring's developmental trajectory, survival probability and behaviour through an increase in the concentration of testosterone in the egg yolk. Chicks from experimental females had a lower body mass at age 3 days, followed by a faster growth rate during the rapid growth phase, a slower growth rate during the slow growth phase and larger tarsus at age 15 days (only male offspring). Additionally, experimental chicks exhibited a lower breathing rate. However, female exposure to stronger competition for nest cavities during nest construction did not affect testosterone concentration in the egg yolk. Differential testosterone deposition in yolk is therefore apparently not the underlying mechanism of the effects observed, which may be attributed to changes in females' parental behaviour triggered by competition for breeding sites.

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Interspecific Density Influences the Adaptive Significance of Provisioning Coordination Between Breeding Partners

Cited by 3 publications

References 33 publications

Brood sex ratio modulates the effects of extra food on parental effort and sibling competition in a sexually dimorphic raptor

Brood sex ratio modulates the effects of extra food on parental effort and sibling competition in a sexually dimorphic raptor

Coordination of care reduces conflict and predation risk in a cooperatively breeding bird

Competitive events during nest‐building influence offspring growth and behaviour, but not testosterone deposition in the egg yolk in Western Bluebirds (Sialia mexicana)

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