Hatching asynchrony and offspring sex influence the subsequent exploratory behaviour of zebra finches

The ecological and evolutionary consequences of variation in behaviour between individuals are well studied, yet the causes of such variation remain poorly understood. Parents can generally exert a great deal of influence on the early life of their offspring, so one possibility is that the mode of parental investment determines subsequent offspring behaviours. In birds, hatching asynchrony occurs when females begin incubation prior to clutch completion, and the subsequent hatching regime creates phenotypic disparities between early and late-hatched offspring. By experimentally manipulating hatching patterns in zebra finches, Taeniopygia guttata, we examined the influence of hatching asynchrony on subsequent exploratory behaviour during adulthood. Late-hatched birds from asynchronous broods explored the novel environment more than their siblings which hatched earlier or came from synchronous broods, although there were no differences in exploratory behaviour towards a novel object. Additionally, females were bolder towards a novel object than were males, independently of hatching regime, but there were no sex differences in exploration of the novel environment. Our results support the idea that both hatching asynchrony and sex have previously underappreciated influences on offspring behaviours, and highlight the importance of variation in parental investment in generating and maintaining behavioural variation. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.