Great Blue Heron

The great blue heron is a commonly encountered resident species of the Tittabawassee River, often seen stalking its prey through shallow waters along the riverbank. Our research aims to verify that the great blue heron population that resides within the Tittabawassee River floodplain is not experiencing adverse effects from site-specific contaminants, specifically dioxins and furans.

Great blue herons possess many ideal attributes of a study species for assessing bioaccumulative compounds in the environment, including being located near the top of the aquatic food chain, being a long-lived species, having a widespread distribution, and displaying territorial foraging behavior.

To determine their dietary exposure to contaminants, site-specific diets of the great blue heron are determined through the collection of prey remains and observations of foraging behavior. These prey items are then collected from the study area and analyzed for contaminant concentrations. For the great blue heron, this includes fish, crayfish, and amphibians. These collections allow us to estimate the concentration of contaminants great blue herons along the Tittabawassee River are exposed to through their diet.

Contaminant concentrations in the tissues of great blue herons are also analyzed to verify that their exposure has been characterized correctly. Specifically for the great blue heron, tissues collected include adult and nestling blood plasma, eggs, and nestling tissues.

The health of great blue heron populations is assessed through the evaluation of productivity, including nest success, clutch size, and fledgling success.

Great blue heron data have been collected from reference areas in Sanford, Michigan, and the Pine and Chippewa rivers in and around the Chippewa Nature Center to downstream of Midland, Michigan, ranging to the Shiawassee National Wildlife Refuge.

Integrating the findings from all lines of evidence will provide us with the information necessary to estimate the risk of adverse effects to great blue herons residing within the Tittabawassee River floodplain.