Breeding success of the European Starling Sturnus vulgaris after a recent invasion in Argentina

Abstract

The European Starling [Sturnus vulgaris] is an invasive bird that it is quickly expanding throughout Argentina. Therefore, breeding success data and its relationship with environmental characteristics are necessary to count with a knowledge base line and potentially diagram control actions. We monitored European Starling nests (n=100 nests) in a native forest of Buenos Aires province (Argentina), during 2020-2021 and 2021-2022 breeding seasons. We estimated breeding parameters for the population and measured nest-site features at different spatial scales to assess their relationship with nest survival and productivity. Starling started breeding earlier than native species, they raised three fledglings per successful nest, estimated nest success chance was 38%, and seven breeding pairs raised two successful broods. There was a negative relationship between daily survival rates and diameter at breast height of the nest-tree. This pattern may indicate that preservation of mature trees would help to reduce starling nest success rate, although our results were not conclusive. Moreover, starling nest survival and productivity were considerably higher than those of native cavity-nesting species breeding in the same area, which suggests their population grows at a comparatively higher rate. Given our results, and the previously reported starling aggressive behavior to native species and worrying expansion rate, it is possible that the populations may need to be controlled soon, especially if starling reaches areas, such as northern Argentina, inhabited by several threatened cavity-nesting species.