Highgrade logging and nest-site limitation in cavity-nesting birds of a threatened subtropical moist forest

COCKLE, KRISTINA; MARTIN, KATHY

San Diego, California

Simposio; COS/AOU/SCO 2010 Joint Meeting; 2010

Cooper Ornithological Society/American Ornithologists' Union/Society of Canadian Ornithologists

Highgrade logging is a widespread anthropogenic disturbance that removes the economically valuable trees in many tropical rainforests, perhaps reducing cavity availability below a critical threshold for cavity-nesting birds. From 2006 to 2009 we assessed the availability and occupancy of natural cavities and conducted a BACI nest box addition experiment to determine whether nest sites were limiting for cavity-nesting birds in primary and logged Atlantic forest in Argentina. Logged forest had half the basal area and 9 times fewer cavities, compared to primary forest. Birds occupied only 25% of cavities overall, but 80% of cavities 55-100 cm deep. The density of breeding pairs increased in both logged and primary forest after nest box addition. Nest site availability appears to limit breeding density for at least some species of secondary cavity-nesters, even in primary forest. Conventional logging reduces breeding density further by removing key nest sites. We recommend preserving the largest live trees >100 cm diameter in logged forest and agricultural areas.