American Oystercatcher benefits from a heterogeneous landscape to breed in an urbanized area in southern Brazil

Abstract

Urbanization is a major form of landscape transformation that often results in habitat degradation and loss for birds. However, effects on avian populations are trait- and context-dependent, and persistence at urban patches is likely to be a function of habitat availability at the landscape scale. Here, we aimed to assess the breeding performance and foraging ecology of a widespread shorebird, the American Oystercatcher Haematopus palliatus, during the 2017–2018 and 2018–2019 breeding seasons at a small urban beach surrounded by a heterogeneous landscape in southern Brazil. Twelve pairs were able to breed consistently and successfully fledge offspring in 20% of nesting attempts at the urban site, with overall productivity of 0.37 fledglings per pair. Food remains collected within seven successful nesting territories and stable isotope analysis in blood samples of adults and chicks indicated that oystercatchers relied on invertebrates from both sandy beaches and rocky shores as food resources. Furthermore, eight out of 21 color-marked individuals from the urban beach were consistently recorded using an insular marine protected area\u2009~\u20092\xa0km offshore, revealing a connection between unprotected and protected habitat patches. Although oystercatchers had to perform multiple foraging trips in order to collect food, the ability to explore different environments in the landscape may be critical in the region, especially with human disturbance at its peak on beaches during the summer. Our findings suggest that shorebirds breeding in urban areas may rely on heterogeneous landscapes, where distinct and protected habitat patches can provide complementary resources that allow breeding successfully.