Sex differences in parental care in a Corsican Blue Tit Parus caeruleus population

Parental behaviour of Blue Tits Pants caeruleus was video-recorded and anal ysed in an insular Mediterranean population that is believed to be adapted to food-limited conditions of an evergreen woodland. The population undergo es high external parasitism by blowflies (Protocalliphora). Contribution of male and female mates to parental care of nestlings was assessed when the nestlings were 13 days old (fledging takes place 21-22 days after hatching) to examine whether the sexes differ in their parental roles. Males brought a higher proportion of caterpillars, the optimal food for nestlings, than females. The caterpillars delivered by males were also larger. We suggest t hat males were more selective than females in prey choice because females w ere more time-constrained as they spent more time at the nest and their vis it rate was higher. In addition to feeding nestlings, female Blue Tits perf orm nest sanitation and mending at all nestling stages. The only aspect of nest sanitation shared with males is the removing of faecal sacs, this acti vity being done by the males at a higher rate than in the case of females. We suggest that in the studied Blue Tit population, the sex differences in prey selectivity and feeding frequency result from the fact that females ha ve to undertake especially intensive nest sanitation in response to high bl owfly infestation. We would expect different patterns of parental care in n on-parasitised populations living in rich habitats.