Influence of habitat structure on the occupancy patterns of threatened insectivorous birds of the Atlantic Forest
Passive acoustic monitoring; Pernambuco Endemism Center; Fragmentation; Arbimon; Conservation;
The Atlantic Forest is the second largest forest in South America, considered a biodiversity hotspot for being one of the most diverse biomes in the world and facing serious threats due to increasing ecosystem degradation. Birds constitute a particularly affected group by Atlantic Forest degradation, with many facing imminent extinction threats resulting from habitat loss caused by deforestation. To prevent biodiversity losses, it is essential to understand the effects of habitat fragmentation and assess how species respond to landscape changes. Occupancy modeling has been a widely used approach to investigate species persistence in fragmented landscapes. Through this approach, it is possible to identify priority areas, enabling the creation of conservation units, and to support the formulation of more effective public policies. The aim of this study was to test how habitat characteristics, at different spatial scales, affect the occupancy of threatened insectivorous birds in Atlantic Forest fragments. We conducted the study in 11 forest fragments in the states of Rio Grande do Norte and Paraíba. Species detection was performed using autonomous recorders distributed at eight randomized points in each fragment. We collected habitat information at three spatial scales: landscape scale, fragment scale, and micro-habitat scale. The target species were threatened insectivorous birds of the Atlantic Forest. The occupancy probability of each species (ψ) was estimated using static occupancy modeling, which considers imperfect detection. The analyses were performed using the MARK program. Among the threatened species occurring in the northeastern Atlantic Forest, six were recorded: Xenops minutus, Herpsilochmus pectoralis, Conopophaga cearae, Picumnus pernambucensis, Xiphorynchus atlanticus, and Automolus lammi. Overall, the occupancy of all species was influenced by micro-habitat and fragment variables, and only X. atlanticus was influenced by landscape variables. The species responded differently to variables at the various proposed scales. Notably, fragment and micro habitat-associated variables stood out, demonstrating to be the scales with the highest number of variables influencing species occupancy. The lowest occupancies were for X. atlanticus (ψ = 0.001), A. lammi (ψ = 0.003), P. pernambucensis (ψ = 0.02), and C. cearae (ψ = 0.08), while the highest were for H. pectoralis (ψ = 0.16) and X. minutus (ψ = 0.89). We emphasize the crucial importance of conducting studies that assess the effects of fragmentation at multiple scales to obtain valuable information and promote the conservation of threatened forest birds in the Neotropical region.