Padrões de ocupação e uso de habitats costeiros por aves limícolas migratórias na porção semiárida do litoral brasileiro

Abstract

Many shorebird species are associated with coastal ecosystems during their annual migratory movements between breeding and overwintering areas. The semi-arid coastal region of northeastern Brazil presents a vast landscape of suitable habitats for these birds. Investigating the use of these habitats by shorebirds as a function of landscape structure and anthropic disturbances is a useful approach to better understand their occupancy patterns in the semi-arid region. In 2022 and 2023 we conducted n=3 independent data sampling campaigns, representing n=111 individual 1km long transects, totaling 804 km, covering the entire coastline of Ceará and part of Rio Grande do Norte. Presence/absence data for the species (Calidris canutus, Calidris pusilla, Limnodromus griseus and Numenius hudsonicus) were collected by means of visual observation using binoculars and spotting scopes. Specific habitat characteristics and other variables, such as proximity to particular habitats, human occupations, and degree of disturbances related to tourism activities were recorded during each transect. In addition, information on landscape variables such as land cover in different classes was collected using satellite images. We analyzed the influence of environmental variables on the occupation of the species through static occupation models, using the MARK program. The three most influential variables in the distribution of the species were the distance from estuaries, urban area coverage and aquaculture. The response of species occurrence along the gradient of variables showed that C. canutus had the lowest occupancy among the species (ψ = 0.31), followed by L. griseus (ψ = 0.44), N. hudsonicus (ψ = 0.71), and C. pusilla (ψ = 0.72). These results indicate the influence of landscape structure and vulnerability of shorebirds to anthropogenic impacts, especially related to habitat loss during the wintering period on the semi-arid Brazilian coast. Our results will help to inform conservation strategies and better define the ecological requirements of this threatened species during the greater part of its non-breeding periods.