Temporal variation in the abundance of two species of thrushes in relation to fruiting phenology in the Atlantic rainforest
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When fruit resources in tropical forests are scarce, frugivorous birds might track fruiting by expanding their home-ranges or by moving. We tested whether the abundance of the Yellow-legged Thrush (Turdus flavipes) and White-necked Thrush (T. albicollis) is correlated with the fruiting of the dominant palm tree (Jucara Palm, Euterpe edulis) and fruiting within the tree community as a whole in three Atlantic rainforest types (restinga, lowland, and premontane forests) in south-eastern Brazil over 3 years. We monitored abundance of the two species of thrush and their consumption of fruit, and fruiting patterns of Jucara Palms and the tree community as a whole. Jucara Palms accounted for 45 and 28% of the feeding bouts of Yellow-legged Thrush and White-necked Thrush. The abundance of Yellow-legged Thrushes was positively correlated with fruiting of Jucara Palms, but not to fruiting of the tree community, in all forest types. White-necked Thrushes ate a greater diversity of fruits and its abundance was neither correlated with fruiting of Jucara Palms or to fruiting of the tree community. We suggest that fruits of Jucara Palms constitute a paramount food resource for Yellow-legged Thrushes and may influence movement and abundance of the species in different vegetation types and elevations in the Atlantic rainforest, whereas White-necked Thrushes employ other feeding strategies to persist in periods of fruit scarcity.