Volunteers Provide High Quality Citizen Science

Broad-winged hawks can look like a swarm of bees as they move from one column of warm air to another.
Credit: J.S. Jourdan

Volunteers counted more than 14,000 broad-shouldered hawks on each of four days in September this year for the Detroit River Hawk Watch.
Credit: J.S. Jourdan


The annual hawk watch at Detroit River International Wildlife Refuge attracts many eager birders.
Credit: Joan Zeller Bonin

December 21, 2015 – For the eighth consecutive year, a cadre of volunteers -- tallying daily from September 1 through November 30 – has completed an annual count of migrating birds of prey over the Detroit River. Seventeen species were counted, totaling 159,510 individual birds – hawks, eagles, falcons and vultures -- including more than 14,000 broad-winged hawks counted on each of four days in September.


The count was initiated by an avid birder in 1983 and maintained by other nonprofit organizations until 2008, when Detroit River International Wildlife Refuge became the official coordinator.  The count is now supported through fund-raising by the refuge Friends organization, the International Wildlife Refuge Alliance. Detroit River Refuge draws thousands of bird watchers annually. 


Detroit River Hawk Watch maintains a daily journal and photo gallery. The data include not only raptor migration information, but also weather, incidental wildlife sightings and phenology notes. Daily counts are sent to the Hawk Migration Association of North America, hawkcount.org, which also tracks hawk counts across the rest of the United States.


“The migration of birds of prey over the Detroit River is the largest autumn passage of broad-winged hawks and turkey vultures in the Great Lakes, and North America’s leading site for red-shouldered hawk,” says Detroit River Refuge manager John Hartig of the refuge that is within sight of industrial smokestacks.


A team of about a dozen refuge volunteers and one contractor count the birds from 8 a.m. until 4 p.m. each day. Broad-winged hawks arrive in September, says refuge wildlife biologist Greg Norwood, They appear like a swarm of bees as they move from one column of warm air to another as they travel from Ontario, Canada, to northern South America. After that, red-shouldered hawks, golden eagles and turkey vultures arrive at Detroit River Refuge.


Because the hawk watch is a major contributor to regional and continental population estimates, “the program also demonstrates the benefit of long-standing, high quality citizen science programs,” explains Hartig.


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