Electronic Thesis and Dissertation Repository


Master of Science




Hobson, Keith A.


Farmland bird populations have experienced declines with increasing agricultural intensification for which the leading hypothesis is a reduction of prey insects. This may be especially relevant for aerial insectivores whose primary diet is aerial insects. For this thesis, I examined nestling body condition and used stable isotopes (δ13C, δ15N) and fecal DNA barcoding to determine the diet of a farmland breeding aerial insectivore, the Barn Swallow (Hirundo rustica), within an agro-ecosystem in Southern Ontario, Canada. Nestling body condition was positively affected by agricultural intensification, but all benefits were lost by the pre-fledging stage and with no effect on productivity. Stable isotopes indicated that nestling diet was derived from within agro-ecosystems. While nestling diet breadth was negatively affected by agricultural intensification, I found evidence for a robust dipteran diet unaffected by landscape. My results provide little evidence of long-term negative repercussions to breeding within agriculturally intense landscapes for the Barn Swallow.