Bird preferences for fruit size, but not color, vary in accordance with fruit traits along a tropical elevational gradient

Birds constitute one of the most important seed dispersal agents globally, especially inthe tropics. The feeding preferences of frugivorous birds are, therefore, potentially ofgreat ecological importance. A number of laboratory-based and observational stud-ies have attempted to ascertain the preferences of certain bird species for certainfruit traits. However, little attention has been paid to community-wide preferences offrugivorous birds and the impact this may have on fruit traits on a broader scale. Here,we used artificial fruits of different colors and sizes to investigate community-widefruit trait preferences of birds at three sites along an elevational gradient in PapuaNew Guinea. We recorded attack rates on artificial fruits as visible impressions madeby a bird's beak during a feeding attempt. We also measured the colors and sizes ofreal fruits at each site, and the gape widths of frugivorous birds, allowing for compari-sons between bird feeding preferences and bird and fruit traits. Regardless of eleva-tion, red and purple fruits were universally preferred to green and attacked at similarrates to one another, despite strong elevational patterns in real fruit color. However,elevation had a significant effect on fruit size preferences. A weak, non-significantpreference for large fruits was recorded at 700 m, while medium fruits were stronglypreferred at 1700 m and small fruits at 2700 m. These patterns mirror those of bothreal fruit size and frugivorous bird gape width along the gradient, suggesting the po-tential for selective pressure of birds on fruit size at different elevations