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Monitoring birds - Protecting waters - Inspiring change
2026 Colonial Waterbirds (herring gull) Field Season
Herring gulls nest in remote areas and on islands that require access by boat. WOWRI was out in June to monitor and sample herring gulls on Bellow Island in Traverse Bay, Michigan, also known as Gull Island Bird Sanctuary and owned by the Leelanau Conservancy.
This spectacular site is a nesting ground for herring gulls, ring billed gulls, Caspian terns and cormorants. Our lead researcher, Dr. Keith Grasman, from Calvin University, and his students are studying the colony here and also in Saginaw Bay.
Preliminary findings revealed ongoing immunosuppression and elevated egg infertility and embryonic mortality in herring gulls at three colonies in ecosystems contaminated with PCBs and dioxins and emerging contaminants such as PFAS.
Researchers also found a cross-billed herring gull chick in Saginaw Bay. “It is concerning that we are still seeing these deformities and embryonic mortality today at PCB and dioxin contaminated sites,” says Dr. Keith Grasman, WOWRI affiliated researcher from Calvin University. “We are also seeing low populations of Caspian terns, a state-threatened species, in Saginaw Bay. We found only 8 nests in 2026, where in 2021-2023 we observed between 100-150 nests on Channel-Shelter Island.
WOWRI Executive Director, Jennifer Day, is out with the team on Bellow Island. Dr. Grasman and a student are in the background, weighing, measuring and drawing blood to samples to later test for toxic chemicals.
Our work area is kept tight and near the shoreline as to limit disturbing the birds and nests. Hard hats and protective clothing are needed as gulls can be aggressive when protecting their young.
Colonial water birds are fish eating water birds that live in colonies, such as herring gulls. Because they are high in the food chain, they concentrate toxins, such as PCBs and PFAS in their blood. They are excellent indicators of water quality in the local area and environmental health.
Photos of the 2026 Field Season
