Sex roles in parental care in a species with precocial offspring and frequent brood desertion

Biparental care can be favoured when offspring care by both parents provides a stronger fitness incentive to parents than deserting their offspring. In species with precocial offspring, the burden of care is expected to be comparatively low, facilitating desertion by one parent and uniparental care by the abandoned partner. However, care patterns can vary widely between and within precocial species, with some parents deserting their offspring, while other families remain biparental. Understanding the details of the care delivered by males and females in families before desertion is important to provide insight into the mechanisms that influence the stability of biparental care. Here we used detailed behavioural observations from the brood care period to investigate the balance of care between male and female parents in a well-studied precocial shorebird, the Kentish plover, Charadrius alexandrinus, both within families where females subsequently deserted and within families that remained biparental until the offspring were independent. We found that both males and females expressed all care behaviours (brooding, vigilance and brood defence) characteristic of precocial species, and we utilized quantitative mutual entropy analyses to show that the division of parental labour (i.e. care task specialization) was unrelated to the maintenance of biparental care. We also found that while males and females provided broadly similar levels of care, there were subtle differences: females typically delivered slightly more care than males across offspring development, suggesting that sex differences in self-maintenance may underlie sex differences in care. Together our results indicate minor differences in the care patterns of males and females, consistent with theoretical predictions that the division of labour should be limited in populations with frequent desertion and uniparental care.