Highway noise decreases the abundance of an understory rainforest bird

ABSTRACT Highways are structures that cause major impacts and threats to biodiversity. We analysed the effects of a highway on the abundance of the Rufous-capped Antthrush (Formicarius colma) in the stretch that intersects the Sooretama Biological Reserve, located in southeastern Brazil. Data were collected using the point-count census method, with points located on the forest edge near the highway, the forest edge near a pasture and random points in the interior of the forest area. Noise was recorded at each point in all areas and related to the abundance of antthrushes. Across habitat types, Rufous-capped Antthrushes were least abundant at the highway-edge, intermediate at the pasture-edge, and highest at the interior of the forest. Within habitat types, species abundance was highest in points 600 m away from the pasture but only in points 800 m away from the highway. The abundance of antthrushes was inversely correlated to noise, irrespective of habitat type (highway or pasture). These results suggest that the presence of the highway and the noise it produces are important threats to the Rufous-capped Antthrush, decreasing its abundance and possibly constraining movements across the highway. For a regionally threatened bird, these impacts could be significant for species viability.