Abstract
Parental behaviour of Blue Tits Parus caeruleus was video-recorded and analysed in an insular Mediterranean population that is believed to be adapted to food-limited conditions of an evergreen woodland. The population undergoes 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 that males were more selective than females in prey choice because females were more time-constrained as they spent more time at the nest and their visit rate was higher. In addition to feeding nestlings, female Blue Tits perform nest sanitation and mending at all nestling stages. The only aspect of nest sanitation shared with males is the removing of faecal sacs, this activity 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 have to undertake especially intensive nest sanitation in response to high blowfly infestation. We would expect different patterns of parental care in non-parasitised populations living in rich habitats.