PARENTAL BEHAVIOR IS UNRELATED TO EXPERIMENTALLY MANIPULATED GREAT TIT BROOD SEX-RATIO

Parental investment may be biased with respect to parental sex or offs pring sex or there may be an interaction between parental and offsprin g sex. We investigated whether any of these types of bias occurred in great tits, Parus major. By sexing chicks using random amplified polym orphic DNA (RAPD) markers and subsequently moving chicks between brood s, we were able to manipulate broods early in the nestling period to g ive all-male, mixed-sex and all-female broods. Provisioning behaviour (total feeding rate, proportion of feeding visits by the male, prey si ze, visit duration and proportion of visits in which a faecal sac was removed) was measured for broods aged 8-9 and 11-12 days. Nest defence behaviour was measured for 15-day-old broods. Parental weight, the oc currence of second broods and overwinter survival of the parents were also analysed, There were some differences in parental care between th e parents: males made the majority of feeding visits and were more vig orous in nest defence. However, there was no evidence that parental ca re varied in relation to brood sex ratio. or that there was an interac tion in parental tare between parental sex and brood sex ratio. (C) 19 98 The Association for the Study of Animal Behaviour.