Range-wide site-occupancy modeling of Red-winged Blackbirds (Agelaius phoeniceus)

Abstract

Globally, habitat loss and land conversion are major drivers of bird population decline. To halt the decline, it is essential that habitat conservation and restoration efforts are based on an understanding of how individual species use their habitat. Here, we examine habitat use by Red-winged Blackbirds (Agelaius phoeniceus) by quantifying their probability of occurrence in different land cover types and in association with varying degrees of habitat modification across most of the species' range. To do so, we used the citizen-science eBird dataset, in combination with MODIS land cover data to model site occupancy for two breeding seasons and related presence/absence to the Global Human Modification Index. We found that Red-winged Blackbirds occupy rural and suburban habitats at higher probabilities than they do habitats with high levels of urbanization, and at similar or higher probabilities than they do their historic, natural habitats. Furthermore, we found that occurrence probability peaks at intermediate values of the Global Human Modification Index. The results were consistent across most ecoregions and the geographic range of the species, confirming that the Red-winged Blackbird is a suburban-adaptable species, persisting in moderately disturbed environments. Although more research is needed to understand the ecological and evolutionary consequences of this pattern of habitat use, our results provide novel data on Red-winged Blackbird habitat use in the midst of increasing urbanization. More broadly, they provide insight into how common, widespread avian species may be affected by anthropogenic disturbance and highlight the importance of rural and suburban environments in urban ecology and evolution.