Distribuição e variação sazonal das aves limícolas na faixa litorânea entre o povoado de “Miaí de Baixo” e a foz do Rio São Francisco (Alagoas, Brasil)

Abstract

Shorebirds form a distinctive group of avian species that thrive in wetlands with shallow water depths, typically not exceeding a few centimeters. Many of these species are known for their migratory habits, engaging in seasonal and cyclical journeys between their recognized breeding grounds and other locations where they rest and feed. The coastline of Alagoas plays host to some of these avian travelers, often originating from the northern boreal regions and heading south during the winter, in pursuit of more hospitable climatic conditions. Alagoas lacks studies on this vital component of biodiversity, a gap that obstructs our understanding of the state's pivotal role in the conservation of these migratory shorebirds. Even though our knowledge about these avian wonders in Alagoas remains limited, the extreme southern coast of the state enjoys national recognition for its importance in the conservation of shorebirds. The establishment of the Environmental Protection Area (APA) of Piaçabuçu was a significant step toward safeguarding crucial feeding grounds for these migratory birds. In our quest to expand our understanding of the dynamics of shorebirds in this region, our study sought to shed light on the avian population through biweekly samplings of bird sightings along the sandy stretch spanning from the Miaí de Baixo village in Coruripe, AL, to the mouth of the São Francisco River in Piaçabuçu, AL. This stretch covers 38 kilometers of beach, and our samplings were thoughtfully designed and executed to detect seasonal fluctuations in bird abundance and observe species distribution patterns within the area. Our samplings involved ten motorized linear transects, each four kilometers in length, along which we meticulously recorded, photographed, and georeferenced the birds we encountered. The data we gathered were then meticulously compared across different transects, taking into account the unique environmental conditions and human-induced disturbances that could affect bird populations. Over the course of 103 sampling campaigns conducted from September 2016 to August 2021, we were able to identify 37 bird species in total, including 24 considered residents, 11 boreal migratory species, and 2 austral migrants. Among them, we encountered eleven shorebird species, seven of which were migratory. Notable among these constant species were Calidris alba, Charadrius semipalmatus, Arenaria interpres, Pluvialis squatarola, and Vanellus chilensis. The section encompassing the Pontal do Peba village stood out with the highest number of individuals, species richness, and bird diversity. This area boasts an extensive reef that emerges during low tide, making it particularly attractive to these species. Considering all recorded migratory shorebirds, it can be observed that the average monthly abundance of these animals begins to rise in September, remaining elevated until April. The fewest migratory shorebirds were recorded in the investigated area between May and August. In summation, this study points to the importance of this region as a significant habitat for migratory shorebirds from the northern hemisphere, serving either as a wintering haven or a vital stopover location for birds in transit. Consequently, preserving these sites, especially the reef near the Pontal do Peba village, becomes na essential and urgent undertaking in the realm of conservation.