Fire Effects on Bird Communities From Seasonally Flooded Forests Along Amazonian Black Water Rivers of the Negro River Basin

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ABSTRACT Aim Fire significantly contributes to Amazonian degradation, with igapó forests (seasonally flooded by blackwater rivers) being especially vulnerable. Igapó forests support species adapted to seasonal flooding, making fire a critical threat to these specialised organisms. Birds, due to their habitat specialisation, can provide insight into fire's impact on this environment. We investigated how fire events over time affect bird species richness and composition in igapó forests of the Negro River basin. Location Negro River basin, Northwest Amazon. Methods We conducted bird surveys at 55 sites using autonomous recorders, totalling 2365 h of recordings. Sites included 18 control areas (igapó forests without fire from 1984 to 2022) and 37 burned sites (fire occurrence from 1984 to 2017). We compared bird species richness and composition across igapó treatments and analysed the effects of canopy cover and understorey density changes due to fire. Results Burned areas showed higher bird species richness than unburned areas. Species composition was more similar in areas burned more than 20 years ago compared to recently burned areas (< 10 years), although full recovery was not achieved. Species replacement was the main component affecting beta diversity. Canopy cover was the only variable directly influenced by time after fire. Both bird species composition and richness were directly affected by time after fire, though composition was also indirectly influenced through canopy cover. Main Conclusions Fire has a direct effect on species richness and composition. Canopy cover is more affected by time after fire than understorey density, also influencing bird species composition. A period of 38 years appeared insufficient for the full recovery of the bird community. Urgent measures for fire monitoring, preservation, and restoration of igapó remnants are essential.

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