EFFECTS OF HABITAT FRAGMENTATION ON PROVISIONING RATES, DIET AND BREEDING SUCCESS IN 2 SPECIES OF TIT (GREAT TIT AND BLUE TIT)

The aim of this study was to examine the effects of forest fragmentati on on the ability of parent birds to provide their young with an adequ ate food supply. To examine whether prey population densities of the g reat tit (Parus major L.) and the blue tit (P. caeruleus L.) vary betw een study areas in different forest size classes we compared provision ing rates and chick diet and related these parameters to breeding succ ess. We filmed 217 nests over two breeding seasons and collected data on frass fall as a general estimate of caterpillar availability. Nests which were attended by none or one parent only during filming (n = 46 ) were excluded from the analyses. In both years and for both species feeling rates were highest in the smallest fragments and lowest in the large forest. There was also a suggestion that differences in feeding rates between areas vary between years. We found no consistent tenden cy for prey size to change with forest size, although both species bro ught slightly smaller prey items to the nest in the smallest forest fr agments and feeding rates correlated negatively with prey size. Caterp illars were the main item fed to nestlings, in both species. We found no evidence to suggest that either frass fall or the proportion of cat erpillars in the diet varied with forest size. There was also no corre lation between mean frass fall and the total number of caterpillars br ought to the nests, in either species. Breeding success, as measured b y clutch size, brood size, fledging weight and fledging success, did n ot differ between the small fragments and the large forest, in either species. There was also no relationship between provisioning rate (as concerns volume of prey fed to nestlings and the quality of chick diet ) and breeding success parameters. In conclusion, this study does not suggest suboptimal foraging or breeding conditions in small fragments compared to a nearby large forest, for either species.