Reports on the ecology and behavior of Ardeidae (herons and egrets) andThreskiornithidae (Scarlet Ibis) species of a reproductive colony in atropical estuary, São Paulo, Brazil

Birds from the families Ardeidae and Threskiornithidae commonly group together into intraspecific and heterospecific aggregations. In Brazil, most studies have focused on ecological and behavioral aspects related to foraging with comparatively few investigations addressing reproductive activities. This study describes a reproductive colony of these two families located in Parque Estadual Ilha do Cardoso on the southern coast of the State of São Paulo, Brazil. We focused on spatial use and behavioral interactions during the breeding season, and recorded six species nesting at the site. Clear differences among species were observed over three breeding seasons, including variations in reproductive period length and colonyoccupation patterns. Additionally, we recorded behavioral interactions such as agonistic behaviors and biparental care in the Scarlet Ibis. Notable differences in nestling and chick behavior were observed, particularly regarding nest agitation and their ability to move through vegetation. Importantly, the initial dynamic of colony occupation was marked by the arrival of a large number of Scarlet Ibis individuals. These findings underscore the importance of long-term studies to better understand the ecological relationships underlying the breeding dynamics of colonial waterbirds.