Response of birds that rely on mature Piedmont Forests of Northwestern Argentina to fire severity

Abstract

Fire is an integral part of the ecology of Seasonal Dry Forests. However, fire severity could be a determining factor in the resilience of these forests. The Piedmont Forest is part of the Neotropical Seasonal Dry Forests, concentrates high species biodiversity and endemism and is one of the most threatened ecosystems of the Andean region. In recent decades there has been an increasing recurrency of fires of high-severity in the Piedmont Forest. Our objective was to assess the effects of fire severity on birds that rely on mature Piedmont Forest of northwestern Argentina. To achieve this, we selected a mature unburnt forest (reference) site and two sites disturbed by fires in the year 2013 of low- and high- severity. During the wet (breeding) and dry (non-breeding) seasons of the year 2016, we carried out 30 bird point counts at each site and recorded birds at different distance categories. We only considered in the analyses bird species that rely on mature forests. To determine bird density at each site we carried out Distance Sampling models. To determine if sites had different bird assemblages, we evaluated the beta diversity through Sorensen dissimilarity index. Our results show that in the wet season, birds that rely on mature forests and resident birds had a lower density in the high-severity burnt site than in the reference site. Also in the wet season, the bird assemblage that rely on mature forests and resident birds had a greater dissimilarity in high-severity burnt site compared to the reference site. In the dry season, only the density of resident birds had a significant lower density in high-severity burnt site than in the reference site. However, no dissimilarity was found for any bird group among sites in the dry season. Birds that rely on mature forests were adversely influenced by high-severe fire in the breeding season, but not in the non-breeding season. This suggests that high-severe fires in the Piedmont Forest probably reduce available nesting resources and diminishes the breeding habitat quality. High-severe fires change the vegetation structure and reduce the habitat quality for resident birds in both seasons. An important management option would be to prevent human-caused high-severity fire and consider prescribed burning to limit the fire severity. In a context where fires are becoming more severe, it is of vital importance the inclusion of information on bird response to fire severity to ensure the conservation of biodiversity.