Turn-Taking Between Provisioning Parents: Partitioning Alternation

Abstract

How parents negotiate over parental care is a central issue in evolutionary biology because it affects the evolutionary outcome of sexual conflict. A recent theoretical model shows that "turn-taking" in provisioning visits by the parents can be an evolutionarily stable negotiation strategy, and empirical studies have shown that parental nest-visits do indeed alternate more than expected by chance. However, such alternation may also be generated by a refractory period, or by correlated temporal heterogeneity (CTH) in provisioning rates of the two parents driven by temporal environmental variation. Here we use a recently developed measure of alternation and a novel measure of CTH in the provisioning rates of pairs to clarify what can be concluded about the occurrence of turn-taking from the provisioning patterns of pairs. First, we show using a simulation model that turn-taking can, by itself, generate both a refractory period and CTH in provisioning rates. Second, we incorporate this insight into a conceptual framework that combines an existing randomization analysis with a novel analytical approach in which "pseudo-pairs" are created by analytically pairing the provisioning sequence of a parent at one nest with the contemporaneous provisioning sequence of the other-sex parent at a nearby nest. This allows us to partition the alternation score into different components. This approach confirms that isolating a component of alternation that can be unequivocally attributed to turn-taking is probably impossible. However, the pseudo-pairs analysis does isolate a component that can be unequivocally attributed to general temporal environmental variation [environmental variation that causes CTH in provisioning rates across (as well as within) pairs]. Third, we use these techniques to partition the alternation score of 17 pairs of great tits Parus major provisioning in the wild. Approximately 8% of the observed alternation score is due to the frequency distribution of the inter-visit intervals, 74% to nest-specific effects on the sequence of inter-visit intervals, and 18% to general effects on the sequence of inter-visit intervals. This last component can be unequivocally attributed to general temporal environmental variation, and is the first empirical demonstration of alternation by free-living provisioning parents being generated by temporal environmental variation.

Songbird parents coordinate offspring provisioning at fine spatio‐temporal scales

“…Empirical studies in songbirds have indicated that individuals modify their provisioning rate in response to the partner's experimentally manipulated behaviour, for example, selective playback, handicapping manipulations (reviewed in Harrison et al, 2009). More recently, it has also been argued that parents alternate their visits at the nest more than expected by chance because they actively monitor and respond to each visit of the partner (Johnstone et al, 2014; Savage et al, 2017; but see Schlicht et al (2016) and Baldan, Hinde, et al (2019). Therefore, parents are behaviourally responsive to each other, but it is not currently known which behavioural mechanisms are underlying these responses.…”

Urban resources limit pair coordination over offspring provisioning

“…Four non-mutually exclusive scenarios are possible. First, spatial heterogeneity (habitat fragmentation), lower food availability or human disturbance in the urban environment may decrease coordinated behaviours because parents may need to forage in different locations 24 or further away from the nest 57 . Empirical evidence in zebra finches Taeniopygia guttata showed that parents foraging independently from each other at different foraging areas decreased synchrony of nest visits 16 .…”

“…parental workload 16 , 21 , 22 , offspring need during development 23 ) affecting pair coordination, a remaining gap in knowledge is how environmental and ecological conditions might limit the ability of parents to coordinate care 24 , 25 . In particular, a study on a great tit ( Parus major ) population in a deciduous forest has shown that pairs in close proximity and recorded on the same day have similar levels of coordination, possibly due to a shared environment (e.g., local weather condition, resource availability) 24 . Therefore, studying the environmental effects on pair coordination is central to understand possible ecological constraints to the emergence of parental behaviours and their fitness consequences.…”

Songbird parents coordinate offspring provisioning at fine spatio-temporal scales

“…2017); (but see Schlicht et al . (2016) and Baldan, Hinde and Lessells (2019)). Therefore, parents are behaviourally responsive to each other, but it is not currently known which behavioural mechanisms are underlying these responses.…”