Impacto do fogo sobre aves em igapós

Abstract

Seasonally flooded black-water forests of the middle rio Negro are susceptible to fires which cause high tree mortality. Post-fire succession is very slow, leaving areas of open vegetation that persist for decades. We studied the impact of igapó fires on bird populations of the middle Rio Negro. By recording bird songs, we sampled 22 intact forests and 22 burn scars. For each of the 44 points we calculated a forest influence index (FII): percent of surrounding area that was forested weighted by distance from the fixed sampling point. For 23 bird species, detections were sufficiently high for further analyses. A NMDS ordination was applied to the raw detection values of these birds. For these same species we also estimated occurrence probabilities corrected by detectability, using a species-specific hierarchical occupation model. The first NMDS axis separated the birds of burn scars from those of intact igapó forest. Both the raw detections and the occurrence probabilities revealed a gradient in community composition clearly associated with burn damage (FII). Nonetheless, only three species showed a significant relationship between burns and occurrence probability. Greater sampling effort may be required to detect environmental effects on more species’ occurrence probabilities.