Happy International Migratory Bird Day! Since its creation in 1993, International Migratory Bird Day (IMBD) has been officially observed on the second Saturday in May. Wisconsin hosts over 225 species of birds that breed here, and then travel to southern countries and continents for the winter. These are birds we refer to as neotropical migrants, because they move from the tropics to the north and back annually. Let’s look at two birds known to inhabit our northern forests.
The Indigo Bunting typically arrives here in May, the end of a 1,200 mile journey from Central America across the Gulf of Mexico north to much of the eastern United States. These birds are common across the entire state, benefitting the most from shrubby, brushy sites of early successional habitat or young forest. The male is a brilliant blue; interestingly, no blue birds (like buntings, blue jays, bluebirds) are capable of growing blue pigment. Rather, these birds have microscopic, prism-like structures in their feathers that allow blue light to reflect away from the bird (and to our eyes.) These birds, basically, are blue the same way the sky is blue. Another interesting fact about Indigo buntings involves their sense of direction. Some small birds are thought to have a sense of earth’s magnetic fields using small metal particles in their brain, like a built in compass. Buntings, though, migrate at night, relying on the position of the stars in the sky. This star map is committed to memory by buntings at a young age-it is not instinctual, but learned.
Another, the Golden-winged Warbler, gets a lot of attention here in Wisconsin. This is because 25 percent of the entire world’s population breeds here. Like buntings, these birds need young forest for part of their life cycle. Unlike the Indigo Bunting, which has been doing well as a species, the Golden-winged Warbler has reduced in population to the point of consideration for listing as a Federal threatened species in 2009. This bird travels 2,800 miles one way from the South American tropics to northern Wisconsin to raise one brood of four or five young before heading home. They arrive mid to late May, and depart in mid-August.
For these birds, and a couple hundred others, Wisconsin offers something extremely valuable, the nesting habitat and food needed to breed, hatch their young, and quickly bring them to a feathered and flying stage to migrate one to two thousand miles south. International Migratory Bird Day was developed so that partners across the country and across continents take time to think about the fact that we all share responsibility for these birds. If they cut down the rain forest to grow coffee, the birds will decline no matter what we do to protect them in Wisconsin. If we change their breeding and nesting habitat, the populations will eventually drop regardless of their overwinter habitat. Hopefully by next May, Rhinelander will be a Bird City, and we will have our own IMBD observation here.
Finally, a reminder to consider keeping your pet cats indoors. Nationwide, domestic cats kill a million migratory birds daily in the spring and summer. Keeping your cat indoors protects young birds learning to fly, adult birds tending nests, and it protects your cat from hazards like car strikes and coyotes. Unfortunately, it is very common, even here in the outskirts of Rhinelander, for cats to be killed or carried off by coyotes. Wildlife groups such as the American Bird Conservancy, the National Wildlife Federation and others have documented the impacts of cats on wildlife.
For more information, check out “Cats Indoors” on the American Bird Conservancy website, abcbirds.org.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR in Rhinelander, and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.