Bird species responses to forest-savanna boundaries in an Amazonian savanna

Abstract

Understanding how species respond to habitat boundaries in a landscape is essential because such responses influence several ecosystem processes and services. However, most studies to date are focused on boundaries between natural and human-made ecosystems, with few investigating species' responses to boundaries between natural habitats. Using a two-step approach, this paper examined how birds respond to gallery forest-savanna boundaries in an Amazonian savanna in Amapá, Brazil. First, we quantified bird species' abundance and boundary sensitivity. Then, we used phylogenetic linear regression to evaluate if five species-level characteristics (trophic level, dispersal ability, body size, niche breadth, and rarity) can be used as predictors of species' boundary sensitivities. We recorded 113 species, of which 67 had enough records to assess their responses to habitat edges. Most species (89%) crossed the boundaries between forests and savannas, with only seven species restricted to one of the habitats. Rarity is the only species trait that predicts a species' boundary sensitivity. Our results show that studies to date have underestimated the magnitude of the biological dynamics occurring along neotropical forest-savanna boundaries.

Keywords

• birds
• forest edges
• gallery forests
• landscape ecology
• riverine forests
• tropical savannas