On Sunday, October 14, 2007, in celebration of National Wildlife Refuge Week, the International Wildlife Refuge Alliance (IWRA), in partnership with the U.S. Fish and Wildlife Service, hosted the “Big Sit!” at the Detroit River International Wildlife Refuge. The “Big Sit!” is a 24-hour worldwide birding event where groups of people gather at their favorite local bird watching location. Participants were surprised by what they experienced at the Refuge.  

Stationed on the observation deck that overlooks Humbug Marsh, participants looked and listened for birds from a seventeen-foot circle. From this world-class bird watching site, they counted 62 different species in less than 24 hours! High species diversity is expected in autumn because migratory birds funnel over the lower Detroit River to avoid flying over Lake Erie. The Atlantic and Mississippi flyways intersect in southeast Michigan and southwest Ontario, making this area exceptional for birding.  Humbug Marsh is considered a key stopover site for migratory birds as they travel from the Arctic to the Tropics.

The highest diversity of birds was found between 6 AM and 10 AM in the morning. The air was alive with bird call notes as the early morning mists burned off Humbug Marsh. Later in the day, Bald Eagles and Osprey swooped down from the sky to snatch fish from the waters of the Detroit River. Kettles of thousands of Turkey Vultures circled and swayed high in the sky on thermals, or updrafts of warm air found over land; in fact, hawk watchers from the Southeast Michigan Raptor Research counted 8,000 Turkey Vultures at Lake Erie Metropark on that day alone!

Birdwatchers spent the night at the marsh expecting to hear many nocturnal migrant birds, such as sparrows and thrushes; however, only four bird species were counted between midnight and 4 AM. Observations were not limited to birds as the loud barks and yelps of coyotes awoke sleepy birdwatchers at 4:30 AM and a handsome mink ambled along the shoreline mid-morning. In total, over 75 people participated in the “Big Sit” over the 24-hour period.

Migrant waterfowl had not arrived yet in southeastern Michigan and southwestern Ontario from their northern breeding grounds on the day of the “Big Sit.” In contrast, participants at the Shiawassee National Wildlife Refuge were able to count all the major waterfowl, such as Gadwall, Northern Shoveler, and American Wigeon. Bird diversity during fall migration is mostly dependent on weather patterns, and food availability and predation determine whether they stop to refuel at a site.