Feeding Ecology of Great Tits (Parus major) and Blue Tits (Parus caeruleus), Breeding in Suburban Gardens

(1) The nestling diet of great tits, Parus major L. (ten pairs), and blue tits, Parus caeruleus L. (eight pairs), breeding in suburban gardens, was recorded using camera nestboxes. (2) Birds breeding in gardens fed their nestlings at a similar rate, and with similar sized prey, to birds breeding in woodland. (3) There was no difference in the type of prey brought by males and females in either species. However, there were significant differences between the species: great tits brought more spiders (Araneae) and Diptera; blue tits more aphids (Hemiptera). Both species brought approximately 15% of the nestlings' food from bird tables (artificial food), although great tits brought significantly more peanuts than blue tits. (4) There was no relationship between the amount of artificial food in the diet, and nestling survival, in either species. (5) The diet of nestling blue tits changed over a 13-day period. Proportionately more spiders were fed to young nestlings (3-9 days), whilst older nestlings (14-15 days) received more artificial food and aphids. (6) The diet of nestling great tits also varied with age: young nestlings (3-9 days) being fed greater than expected numbers of spiders, earwigs (Dermaptera), and Diptera. (7) In both species, nestling diet was not independent of time of day. Blue tits brought fewer Lepidopteran larvae than expected from 07.00 to 16.00 h, and more aphids. Great tits brought more spiders than expected from 08.00 to 13.00 h, and more Diptera from 05.00 to 08.00 h. (8) Both species showed a tendency to bring prey in runs, this being most pronounced for artifical food and aphids in blue tits, and artificial food in great tits. These particular prey items were the only ones to be brought more quickly when in a run of the same prey-type. (9) Comparisons are made with earlier studies of nestling diet, which have been carried out in a variety of woodland habitats. Both species brought fewer Lepidoptera when breeding in gardens, and great tits brought back significantly more Diptera.