Spring migration brings more birds to Wisconsin

It’s amazing to realize that while we sleep, thousands of birds are migrating overhead, winging silently through the night, heading to their summer breeding grounds in the north. Some will stop here in Wisconsin to raise their young, and others fly on to Canada and even the Arctic to reach their breeding grounds.

We’ve learned much about bird migration but that knowledge is rather recent. While some ancient cultures and even early naturalists suspected that birds spent winters in warmer climes, the first real evidence of bird migration, writes Rebecca Heisman in her 2023 book, “Flight Paths,” was when an unfortunate stork was shot outside a German village in 1822. When picked up by the hunter, he found that a large spear had been impaled clear through its neck. Analyses of the spear showed that it was from Africa.

The history of unraveling the mysteries of bird migration is fascinating and well researched in Heisman’s book. She leads us through the use of various devices used to determine the movement of birds, starting with bird banding followed by the discovery of what weather radar can reveal about bird movements.

Some of the newer tools used to track birds include tiny radio transmitters which are attached to birds, the signals from the transmitters tracked first from the ground, then from satellites. Light level geolocators (that track the sun’s position and the time) also attached to birds can identify the bird’s location. Now very sophisticated analyses using stable isotopes from bird feathers, and DNA analyses, are revealing more and more about the movement of our avian friends — many of whom travel widely (some up to thousands of miles) during migration.

These tracking devices winging their way around the world are playing a key role in bird conservation; they are identifying wintering, breeding and stop-over habitats. It’s these areas that are important to protect in order to conserve our bird populations, especially as so many of them are on the decline.

I digress; now back to spring migration. Among the millions of birds winging their way north are warblers, sparrows, finches, shorebirds, raptors, waterfowl, hummingbirds and songbirds. It’s the warblers I’m working on learning more about this spring.

According to one of our favorite bird field guides, “Kaufman Field Guide to Birds of North America” by Kenn Kaufman (Kaufman), there are more than 50 species of warblers in North America. To learn more about 32 warbler species you can see in Wisconsin, check out the Bird Advisors website at www.birdadvisors.com/warblers-wisconsin.

Most warblers are coming to us from their wintering grounds in the tropics (Mexico, Caribbean and Central and South America). They are a beautiful group of birds, many, especially the males, sporting bright color combinations and patterns.

Some of the warbler names reflect their coloring. Consider the black and white warbler, yellow warbler, black-throated blue warbler, cerulean warbler, yellow-rumped warbler, chestnut-sided warbler and common yellowthroat. These names alone are alluring; you want to see them and learn more about them.

Warblers can be elusive. Many spend their time in forest undergrowth, making them hard to see. Many of them flit high up in the tree tops, always on the move. Patience is a requirement while birding, as is a good pair of binoculars, a birding field guide and/or the Merlin App on your phone.

You can train your ear to pick out some of your favorite warbler songs to help identify them. Kaufman describes them as high-pitched, with thin clear notes, buzzes and trills. You may also hear their “chip notes;” listen for “chip” or “tsick” to see if they are nearby. The Merlin App is especially fun and helpful here, as it can identify birds by their songs and calls.

Warblers mostly feed on small insects and some, like the yellow-rumped warbler, also eat berries and therefore, according to Kaufman, arrive earlier in the spring and linger later into fall. The yellow-rumped warbler is a favorite with its overall gray, black and white feathering highlighted with bright yellow patches on top of its head, its sides and on its rump. It is easier than some to identify on the wing.

Bring some joy to your spring by keeping an eye and ear out for the birds. They have traveled far to get here, using their amazing navigation instincts and skills to guide them north. They will reward you with their beauty and songs.

Cathy Carnes is a retired biologist in Oconto who worked with the U.S. Fish and Wildlife Service Green Bay Field Office and, prior to that, with the U.S. Army Corps of Engineers Regulatory Branch in Buffalo, New York. As endangered species coordinator for the USFWS, she helped conserve and recover federally listed threatened and endangered species in Wisconsin.