Fruit size preference in the New Zealand pigeon (Hemiphaga novaeseelandiae)

We investigated whether the New Zealand pigeon Hemiphaga novaeseelandiae (Columbidae) exhibits size-based preferences for fruits. We tested the hypothesis that in small-fruited species, pigeons would prefer larger fruits, but in larger-fruited species, this preference would reverse as the pigeons become increasingly limited by their gape size. We collected undispersed fruits and bird-dispersed seeds of 10 plant species, some over several sites or years (13 datasets in total). We estimated the fruit size of dispersed seeds by fitting regressions of fruit diameter to seed diameter in intact fruits. We were able to predict fruit diameter from seed diameter in 12 of the 13 populations, although the relationship was stronger in single-seeded species than in multi-seeded species. Seven of the 12 populations tested showed a significant difference in seed diameter among undispersed and dispersed seeds. However, our results showed no consistent pattern in fruit size preference by the New Zealand pigeon and did not support our hypothesis. The large-bodied New Zealand pigeon is generally not gape limited and fruit size preferences appear to be independent of mean fruit size.