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1.The potential contribution of vertebrate predators to biological control in orchards has been largely overlooked to date. A few studies have shown that birds reduce numbers of pests, but data are scarce on the effects on the pattern or timing of damage. Consequently, the practical value of birds as biocontrol agents remains unclear. 2. This study considered whether great tits Parus major can reduce caterpillar numbers and fruit damage by caterpillars, and increase biological yield, in an experimental orchard of apple trees with high caterpillar numbers. The outcome would depend on the coincidence of the period during which great tits forage and the period during which caterpillars cause damage. In the first experiment nets were put over trees at different times of the growing season, thus creating different periods during 3. The longer the period of foraging by great tits, from the start of egg incubation until fledging of young, the less the overall pest damage to fruit. Damage caused by caterpillars was greater the later they were removed, from the young apple stage onwards. 4. The effect of great tits on caterpillar damage to apples was small (percentage damage was reduced from 13·8% to 11·2%) but significant (P <0·05), and the yield of fruit increased significantly (from 4·7 to 7·8 kg apples per tree, P<0·05). The only cost to the producer was that of erecting nest boxes (c. 2 ha1) to encourage great tits to breed in the orchard. Depending on the great tits' numeric response to insect densities, their relative impact may be greater at lower densities more typi
Original languageEnglish
Pages (from-to)888-899
JournalJournal of Applied Ecology
Issue number6
StatePublished - 2002

ID: 307441