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

► The causes of variation in behaviour between individuals remain poorly understood. ► We examined if hatching asynchrony influences zebra finch behaviour in adulthood. ► Late-hatched asynchronous birds were more exploratory than early-hatched birds. ► Females were more exploratory than males, irrespective of the test conditions. ► Hatching asynchrony strongly affects offspring behaviours during adulthood.