Barn Swallow (Hirundo rustica) fledglings use crop habitat more frequently in relation to its availability than pasture and other habitat types

Populations of birds that forage on aerial insects have been declining
across North America for several decades, but the main causes of and
reasons for geographical variation in these declines remains unclear. We
examined the habitat use and survival of post-fledging Barn Swallows
(Hirundo rustica), near Vancouver, BC, Canada using VHF radio telemetry.
We predicted that fledgling Barn Swallows hatched in higher quality natal
habitat (pasture) would fledge at higher quality, stay closest to the
nest, disproportionately use higher-quality habitat during the post-fledge
stage and have higher survival rates in the region. Contrary to our
predictions, we found that natal habitat (crop, pasture or
non-agriculture) had no effect on fledgling quality or movement distance.
Barn Swallow fledglings used crop habitat more frequently in relation to
its availability than other habitat types, including pasture. Barn
Swallows had low post-fledging survival rates (0.44; 95% CI: 0.35-0.57),
which could negatively influence the population trend of the species in
this region. While natal habitat had only minor effects, crop habitat
appears to be important for fledgling Barn Swallows and therefore a
decline in this habitat type could have further negative implications for
an already declining species.