The importance of flavour in determining the feeding preferences of bullfinches (Pyrrhula pyrrhula) for the buds of two pear cultivars.
Wild bullfinches feeding on the buds of orchard pear trees are known to prefer the cultivar 'Conference' to 'Doyenne du Comice', which differs in many physical and chemical features. To test the role of flavour cues in determining birds' preferences, chemical extracts of bud material were coated onto hemp fruits presented to bullfinches in cage tests. There were no differences in food consumption according to the presence of bud extracts or an acetone control treatment, but both pear bud treatments produced changes in feeding behaviour. Birds reduced their initial feeding bouts, were more likely to drop fruits, drank water earlier in trials, and removed the fruit coats more quickly than if fruits were untreated or treated only with acetone. In most respects, Comice extract produced stronger effects than Conference extract. Results imply that both cultivars have an offensive flavour, and the stronger reactions to the flavour of Comice match its avoidance by wild birds. Counts of bud damage in an orchard revealed a uniform low level of damage to Comice trees, irrespective of the level of bud loss suffered by neighbouring Conference trees. This is consistent with preferences being partly determined by the relative offensiveness of buds.