McIvor, G. E. | bioRxiv Science

bioRxiv2023

Pair-bond strength is consistent and related to partner responsiveness in a wild corvid

The need to maintain strong social bonds is widely held to be a key driver of cognitive evolution. This assumes that the maintenance of strong bonds is a stable trait that is cognitively demanding but generates fitness benefits, and so can come under selection. However, these fundamental micro-evolutionary tenets have yet to be tested together within a single study system. Combining observational and experimental behavioural data with long-term breeding records, we tested four key assumptions in wild jackdaws (Corvus monedula), corvids whose long-term pair-bonds exemplify the putative social drivers of cognitive evolution in birds. We found support for three assumptions: (1) pair-bond strength varies across the population, (2) is consistent within pairs over time and (3) is positively associated with a measure of socio-cognitive performance. However, we did not find evidence that stronger pair-bonds lead to better fitness outcomes (prediction 4). While strongly bonded pairs were better able to adjust hatching synchrony to environmental conditions, they did not fledge more or higher quality offspring. Together, these findings provide important evidence that the maintenance of strong pair bonds is linked to socio-cognitive performance and facilitates effective coordination between partners. However, they also imply that these benefits may not be sufficient to explain how selection acts on social cognition. We argue that evaluating how animals navigate trade-offs between investing in long-term relationships versus optimising interactions in their wider social networks will be a crucial avenue for future research.

animal behavior and cognition↗

bioRxiv2020

Cooperative nest building in wild jackdaws

Animals create diverse structures, both individually and cooperatively, using materials from their environment. One striking example are the nests birds build for reproduction, which protect the offspring from external stressors such as predators and temperature, promoting reproductive success. To construct a nest successfully, birds need to make various decisions, for example regarding the nest material and their time budgets. To date, research has focused mainly on species where one sex is primarily responsible for building the nest. In contrast, the cooperative strategies of monogamous species in which both sexes contribute to nest building are poorly understood. Here we investigated the role of both sexes in nest building and fitness correlates of behaviour in wild, monogamous jackdaw pairs (Corvus monedula). We show that both partners contributed to nest building and behaved similarly, with females and males present in the nest box for a comparable duration and transporting material to the nest equally often. However, while females spent more time constructing the nest, males tended to invest more time in vigilance, potentially as a means of coping with competition for nest cavities. These findings suggest a moderate degree of division of labour, which may facilitate cooperation. Moreover, some aspects of behaviour were related to proxies of reproductive success (lay date and egg volume). Females that contributed relatively more to bringing material laid earlier clutches and pairs that spent less time together in the nest box had larger eggs. Thus, selection pressures may act on how nest building pairs spend their time and cooperatively divide the labour. We conclude that cooperative nest building in birds could be associated with monogamy and obligate biparental care, and provides a vital but relatively untapped context through which to study the evolution of cooperation. HighlightsO_LIIn wild monogamous jackdaws, mates behaved similarly and cooperated to build their nest. C_LIO_LIFemales built more and called more frequently; males tended to be more vigilant. C_LIO_LIFemales that contributed relatively more to transporting nest material laid earlier clutches. C_LIO_LIPairs that spent more time together in the nest box had smaller eggs. C_LIO_LICooperation may be crucial in light of obligate biparental care and nest site competition. C_LI

animal behavior and cognition↗