Foraging Repertoire of American Oystercatcher (Haematopus palliatus) in Two Different Habitats in an Important South American Wetland

The American Oystercatcher (Haematopus palliatus) is a shorebird with a wide distribution along the coastal regions of the Americas. Similar to other oystercatchers, it primarily feeds on bivalve mollusks, crustaceans, polychaetes, and other invertebrates. In this study, our first aim was to describe the feeding behavior repertoire of the American Oystercatcher at the Lagoa do Peixe National Park, an important wetland for this species in southern Brazil. Initially, we compiled a repertoire of feeding behaviors from existing literature and preliminary fieldworks. Subsequently, ad libitum observations were carried out, varying in duration from 1 to 10 minutes, to quantitatively assess the species' foraging behaviors in both the oceanic beach and lagoon habitats. The behaviors were categorized into three main categories: Search, Capture, and "Mandibulation". As a result, a total of 132 minutes of observation time and 1763 behavioral events were recorded. We observed that the Search and Capture categories had longer durations on the ocean beach, while the "Mandibulation" category was more prominent in the lagoon environment. The specific prey available in each environment influenced the choice of foraging methods, highlighting the American Oystercatcher's flexibility in adapting its feeding strategies. These findings indicate that different environments require different foraging strategies in response to varying food availability.