Enduring rules of care within pairs - how blue tit parents resume provisioning behaviour after experimental disturbance

Arne Iserbyt,Maaike Griffioen,Marcel Eens,Wendt Müller

doi:10.1038/s41598-019-39139-9

Abstract

Sexual conflict over parental investment can result in suboptimal reproductive output. A recent hypothesis suggests that equality in investment, and hence conflict resolution, may be reached via coordination of parental activities like alternating nest visits. However, how robust patterns of care within couples are against temporal disturbances that create asymmetries in parental investment remains as yet to be shown. We here experimentally created such a social disturbance in a wild population of biparental blue tits (Cyanistes caeruleus) when provisioning their nestlings. We randomly caught and subsequently released one of the parents when nestlings were 6 and 12 days old respectively. On average, the parent that was caught did not resume care for nearly two hours. We then compared the levels of individual investment and within-pair coordination before, during and after the absence of the disturbed parent. We show that the remaining parent partially compensated by increasing its provisioning rate, but this compensatory response was strongest in females when nestlings were 6 days old. Once the caught parent returned to feed its nestlings, both parents resumed provisioning at a similar rate as before the disturbance. Likewise, the within-pair alternation level quickly resembled the pre-manipulated level, independent of nestling age or which sex was caught. Thus our experiment highlights the resilience of parental behaviour against temporal disturbances of individual parents.

Highlights

Cooperative behaviour, i.e. the simultaneous or consecutive acting together of two or more individuals[1], often yields mutual benefits
Nest visit rate did not significantly vary throughout the course of the day, a pattern that was consistent for both sexes
The degree of within-pair coordination was consistent throughout the day

Summary

Introduction

Cooperative behaviour, i.e. the simultaneous or consecutive acting together of two or more individuals[1], often yields mutual benefits. It resembles a natural situation in which one of the parents is challenged by, for example, a predator or an intruder Comparing partners in their absolute levels of investment (e.g. feeding rates), as well as their coordinated levels of investment (e.g. alternation) before, during and after the disturbance, enabled us to determine to which extent these behavioural estimates are flexible and whether they potentially became re-established over time. We expect that pair members monitor each other’s activities and speed up or slow down nest visit rate in direct response of the partner’s behaviour, as would be predicted by the alternation hypothesis[15] We expect that this matching response is an efficient way to achieve equality in investment, which would prevent any further exploitation by the formerly absent parent

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