The influence of size, shape, and phenolic content on the selection of winter foods by the Azores bullfinch (Pyrrhula murina)

Abstract

Although the quality of foods may change through the seasons, few studies have assessed shifts in food preferences. I studied winter food selection of the Azores bullfinch to evaluate whether physical characteristics (size and accessibility), or phenolic content of food items better explained changes of winter diet. The birds preferred larger items of all winter foods: seeds, sori and flower buds and more accessible seeds. In autumn, seeds seemed preferred to sori, but in spring birds switched from seeds to sori and flower buds, once the latter became larger. Phenols may influence food preference but they did not explain diet shifts or preferences for individual trees. Food selection is a complex mechanism, depending on the alternatives available and seasonal shifts in food preference may continually change the availability of 'good quality food'.