Fish-eating (Piscivorous) Birds
An afternoon on the river would not be complete without hearing the rattle call of a belted kingfisher letting you know you’ve entered its territory or watching a great blue heron steadily stalking its prey through the shallows. Our research aimed to verify that the populations of these species residing within the Tittabawassee River floodplain did not experience adverse effects from site-specific contaminants (furans and dioxins).
To do this, site-specific diets of each species were determined through the collection of prey remains and observations of foraging behavior. Observed prey items were then collected from the reference and study areas and analyzed for contaminant concentrations. For the great blue heron and belted kingfisher, this included fish, crayfish, and amphibians. These collections allowed us to estimate the concentration of contaminants the receptor species was exposed to through its diet.
Contaminant concentrations in tissues of the receptor species were also analyzed to verify that their exposure had been characterized correctly. The type of tissue collected depended on the receptor and included eggs, nestlings, or blood plasma.
The health of receptor species’ populations were assessed through the evaluation of productivity measurements, which included nest success, number of nestlings per nest, fledgling success and species abundance.
Fish-eating bird data have been collected from reference areas in Sanford, Michigan, and the Pine and Chippewa rivers in and around the Chippewa Nature Center, and study areas downstream of Midland, Michigan, ranging to the Shiawassee National Wildlife Refuge.
Integrating the findings from all lines of evidence provided us with the information necessary to estimate the risk of adverse effects to great blue herons and belted kingfishers that reside within the Tittabawassee River basin.