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LINKING WATER QUALITY AND TREE SWALLOW POPULATIONS ACROSS AN URBAN-FORESTED LANDSCAPE GRADIENT

North American aerial insectivorous birds have experienced alarming population declines in recent decades. Tree swallows (Tachycineta bicolor) forage in riparian areas and rely on a combination of aquatic emergent and terrestrial flying insects. We monitored tree swallow populations across an urban-forested gradient in Columbus, Ohio for three breeding seasons. At seven riparian sites, we collected data on reproductive success and body condition, as well as environmental factors and insect food availability. Preliminary analyses indicate that water-quality parameters including total phosphorus and nitrogen were important predictors of reproductive success (e.g., clutch size, number of nestlings fledged, clutch initiation date). Water turbidity and mercury concentrations were both associated with individual body condition. These results show that shifts in water quality may contribute to aerial insectivorous bird populations via effects on emergent aquatic insects, which represent an energetically-critical prey source. Further, initial evidence suggests that variability in air temperature and humidity are also related to swallow responses, implicating changing climate patterns as an additional factor potentially influencing aerial insectivorous bird populations.

Joseph Corra ( Co-Presenter/Co-Author), The Ohio State University, corra.1@osu.edu;


S. Mazeika P. Sullivan (Primary Presenter/Author), The Ohio State University, sullivan.191@osu.edu;