Seasonal variation in the foraging behaviors of the grey-cheeked fulvetta due to diet changes in the Fushan experimental forest, northeastern Taiwan.

A seasonal change in the diet of the Grey-cheeked Fulvetta (Alcippe morrisonia) was found in a previous study. In this study, we investigated seasonal variations in the foraging behavior of the Grey-cheeked Fulvetta between breeding and non-breeding seasons in the Fushan Experimental Forest, northeastern Taiwan. Attack behaviors, food types, and habitat characteristics of foraging locations of the Grey-cheeked Fulvetta were recorded throughout a complete annual cycle. The results showed that seasonal variations of all aspects of foraging parameters were significant, including attack behavior, food type, vegetation level, perch size, and the phenology of plants used by the Grey-cheeked Fulvetta. During the breeding season, the Grey-cheeked Fulvetta made significantly more-diverse foraging maneuvers for insects, and more often foraged in the subcaopy of larger trees and in areas with sparser vegetation. On the contrary, the Grey-cheeked Fulvetta applied more leg-powered maneuvers for more plant matter at the outer parts of smaller trees or shrubs in the understory during the non-breeding season. The patterns of resource use paralleled phenological changes in the plant species, with more new leaves on trees upon which the Grey-cheeked Fulvetta foraged in the breeding season, and more fruit on trees in the non-breeding season. In conclusion, seasonal variations in foraging behaviors of the Grey-cheeked Fulvetta were significant and mainly attributed to diet changes between the breeding and non-breeding seasons. This study is in accordance with the changing-availability hypothesis and can provide empirical evidence for adaptive evolution of birds' foraging strategies.