Paying attention but not coordinating: parental care in European starlings, Sturnus vulgaris

Abstract

Sexual conflict occurs in biparental species because working together provides shared benefits while incurring individual costs. In birds, coordination of provisioning visits via turn taking has been proposed as a strategy to mitigate this conflict. However, alternation of visits requires that birds have access to reliable information on their partner's behaviour, e.g. through high synchrony of nest visits or short foraging distances (allowing for direct observation of partners). Here we investigated parental coordination in the European starling, a species that forages at considerable distances from the nest (200–1600 m), where there is no evidence that pairs forage together, and where synchrony at the nest appears to be low, so that direct access to information on partners will be variable and limited. There was some evidence that individuals were ‘paying attention’ to their partner's provisioning rate, adjusting their behaviour in response to their partner's behaviour. In first broods, female intervisit intervals that were preceded by a male visit (order of visits: male, female, female) were longer than those that were preceded by a female visit (order of visits: female, female, female). Females and males both responded to mate removal by decreasing their provisioning rates though these returned to preremoval levels the day after removal. This is consistent with ‘matching’ of parental workload not ‘partial compensation’. These results suggest that birds do adjust their behaviour in relation to information about their partner's behaviour or absence/presence. However, despite this, there was no evidence of true coordination via alternation or synchrony (i.e. this was not different from random) in European starlings. • Parental coordination requires information on the partner's provisioning behaviour. • Starlings have long foraging distances and low synchrony at the nest. • Individuals appeared to ‘pay attention’ to their partner's provisioning rate. • Individuals appeared to adjust their behaviour relative to their partner's behaviour. • However, alternation and synchrony were not different from random.