By The Masked Biologist
Special to the Star Journal
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. This year’s theme is focusing on migratory stopover habitat, which is extremely important for these birds that travel thousands of miles, usually in a couple of large, nonstop flights. They can burn a third to a half of their body weight during these flights, so finding the best possible habitat to rest and refuel can mean the difference between life and death. Our area provides stopover habitat for shorebirds and songbirds that nest between here and the Arctic Circle. They use these habitats when heading south in the fall (late summer for shorebirds) as well as the late winter/early spring. If you check out the IMBD website, you will see the 2017 poster designed to honor these stopover habitats and highlight some of the birds that use them.
In addition to stopover habitat, Wisconsin hosts over 225 species of birds that breed here, 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 very young age—it is not instinctual, but a learned behavior.
Another of our breeding bird species, the wood thrush, occupies our more mature deciduous forests. This bird is reclusive, usually heard more than seen. It rustles around in the leaf litter on the forest floor looking for insects to feed upon. It is a rather dull, cinnamon colored bird, its white breast speckled brown. Once you have heard the call of this bird, you won’t forget it.
It has an almost haunting, echoing call. They have a branched voice box, which means they sort of sing a duet with themselves, able to make two different sounds simultaneously. When their eggs hatch, the father does most of the feeding so the mother can start laying and hatching a second brood. This means unlike many other neotropical species, they bring up two batches of offspring a year. Then they head a couple thousand miles south to southern Central America to wait out the winter. The wood thrush is one of the birds featured on this year’s IMBD poster.
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 up to 2,000 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 the condition of their overwinter habitat in the tropics. These birds provide a trans-global link between countries and continents. So go out and buy a cup of bird-friendly coffee and spend some time listening to the wide variety of birds that share our beautiful Northwoods with us!
The Masked Biologist earned a Bachelor of Science degree from a university with a highly regarded wildlife biology program. His work in natural resource agencies across the country provided opportunities to gain experience with a variety of common and rare fish, plant and wildlife species. Follow The Masked Biologist on Facebook. Email questions to MaskedBiologist@charter.net.