Defining Corridor Functions for Endemic Birds in Fragmented South‐Temperate Rainforest

Abstract

Abstract: For five species of endemic understory birds ( families Rhinocryptidae, Furnariidae) inhabiting fragmented temperate rainforest in southcentral Chile, we distinguished between vegetated corridors functioning as living space and those potentially suitable for short‐distance movements only. In the first phase of the study, we surveyed 24 forested corridors ≤50 m wide using passive and song‐playback censuses. Corridor width determined species presence or absence, whereas the number of individuals increased with width and understory vegetation density. Birds were infrequently encountered in corridors ≤10 m wide but were always present in corridors 25–50 m wide. Birds present in intermediate‐width (11–24 m) corridors were detected significantly less often during passive than playback census, suggesting that these birds exhibited conspicuous territorial display less frequently than those present in wider corridors, where passive and playback census yielded similar detection rates. Corridors approximately 10–25 m wide, therefore, may be transitional between corridors too narrow for most regular uses and those sufficiently wide for birds to establish territories. Also, bird abundance decreased as the ratio of corridor length to width ( L / W) increased. Almost no birds were detected in corridors with L / W ≥ 10, suggesting the existence of a threshold value for the influence of L / W on corridor use. In the second phase of the study, taped‐song playback experiments in corridors ≤10 m wide showed that all five species traveled in them for short distances: 52% of respondents moved up to 50 m from forest patches into narrow corridors. Availability of dense understory vegetation was the primary predictor of birds' responses to playback and may determine their willingness to use minimal corridors for short movements. We suggest that corridors for endemic rainforest‐understory birds living in agricultural landscapes of southern Chile can be designed to fulfill distinct functions.