Dinâmica comportamental do atobá-marrom (Sula leucogaster) no Arquipélago de Fernando de Noronha

Abstract

Seabirds are important bioindicators of marine ecosystems. Environmental changes, such as climate alterations and anthropogenic factors, affect the occupation and behavior of several species. The Brown Booby Sula leucogaster (BODDAERT, 1783) is one of the resident species in the Fernando de Noronha archipelago, an oceanic island located in the northeast region of Brazil. This study aimed to evaluate the behavioral dynamics of the Brown Booby in different regions of Fernando de Noronha. Data collection took place between September 23 and October 18, 2023, encompassing three sampling sites on the leeward coast (north-northwest face) and three on the windward coast (south-southeast face) of the main island. Visual samplings were divided between 7 am and 5 pm, conducted through scan and focal animal series, with 11 behaviors categorized into four classes: foraging, resting, interaction, and passage. Parameters of occurrence frequency (FO), point abundance index (IPA), and behavior frequency were analyzed. A total of 806 individuals were counted with an FO of 72.5% and an IPA of 10.1 individuals per sampling, across all study period. The windward coast showed higher abundance (max. 55 individuals) compared to the leeward coast (max. 20 individuals), although the occurrence frequency was similar between both (~73%). The highest numbers of individuals were recorded on Sueste and Caiera beaches (windward coast). A pattern of decline in individual abundance throughout the day was observed, as well as a general decrease in behavior frequency, including the quantity of attempts for deep dives. Resting activity predominated (59.6%), followed by foraging (40.1%), interactions (0.3%), and passage (0.1%), with more events occurring in the windward coast for all categories. Behavioral plasticity in seabirds is advantageous in dynamic regions such as marine environments, where prey availability varies greatly. This study helped understand the behavioral patterns of the local Brown Booby population, which is important for the development of effective visitation management strategies in Fernando de Noronha.