The positive influence of wetlands on reproductive success and body mass in an aerial insectivore is more pronounced in intensively cropped agroecosystems

Weather and land-use changes can act in complex ways to affect species’
annual demographics and distributions. Biodiversity and agriculture are
frequently intertwined, where climatic conditions, such as flooding and
drought, may be exacerbated by intensive agricultural practices.
Understanding how climate change and agricultural land use influence avian
populations is key to retaining biodiversity in working landscapes. Here
we examined a large dataset of breeding Tachycineta bicolor (Tree Swallow)
in Canada’s Prairie Pothole Region (PPR) across eight years at eight sites
representing a gradient in agricultural intensity and wetland
availability, for a total of 42 site-years. We analyzed the influence of
agricultural land use, wetland availability, and seasonal temperature on
Tachycineta bicolor reproductive success and body mass, while testing for
potential interactive and curvilinear effects. As predicted, fitness
measures were negatively affected by agricultural intensity; specifically,
clutch initiation date was later and nestling body mass was lower at
cropped versus non-cropped sites. Also, as predicted, interactions
revealed that the beneficial effects of wetland availability were more
pronounced at cropped sites. Associations between temperature and fitness
measures were less clear but suggested the potential for detrimental
effects of temperature extremes that might also depend on agricultural
intensity. Our results contribute to a growing body of literature
demonstrating the negative impact of intensive cropping practices and the
importance of retaining natural and semi-natural habitats, including
wetlands, in working landscapes to conserve biodiversity and buffer
against temperature extremes and future climate changes.