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The Magic of Migration

Spring 2007 Newsletter

With the lengthening of the days, we can look forward to the arrival of migratory birds. It won’t be too long before we will awaken to the persistent songs and calls of the males seeking nesting territories and mates.

What we are witnessing is a rite of spring that is “as old as time,” even older than the glaciers. The arrival of the birds in spring is always welcome, and a little mysterious. The more we learn about migration, the more we are amazed by nature, evolution and the risks that these beautiful creatures undertake.

The birds we see in the Midwest are either migrants or “temperate residents,” birds that do not migrate. Some species have members that fall in both camps, like bluebirds. Since bird behavior has evolved to improve reproductive success, migration facilitates the chances for bearing and rearing healthy young, primarily due to more available food sources and nesting sites.

Migration is dangerous and costly for adult birds. The annual survival rate for adult migrants is only 50 percent. Migrating birds may be shot, eaten by predators, or die from hunger or exhaustion. It is estimated that more than 100 million disoriented migrants die from collisions with high rise windows! The trade off is that their reproductive success is improved by seasonally abundant food supplies and greater day length. While a lot is yet to be known about migration, it is known that birds that migrate raise more young (4-6) annually compared to their resident tropical relatives (2-3). Temperate residents raise the most young (greater than 6) but have the lowest annual survival rate (20-50%) due to the harshness of winter.
So our migratory birds have evolved to undertake the risks of migration to produce more viable offspring and pass on their genes.

Many aspects of migration are little understood. For example, most birds migrate at night, beginning 30-45 minutes after sunset and peaking around midnight. We are not sure why this is, as most of these birds spend their non-migratory periods out and about during the day. We do know that migrants fly higher over water than they do over land. Songbirds may fly above 12,000 feet over water, apparently to take advantage of favorable winds, and 2100 feet over land.

There are also several theories about what triggers migration. The most commonly held theory is that it is the length of daylight. According to Miyoko Chu in Songbird Journeys songbirds, even captive ones, become restless in the fall: “Ornithologists know this migratory restlessness by the German name, Zugunruhe. Like molt and weight gain in fall, Zugunruhe is triggered by changing day length, ensuring that the birds are ready to leave at the same time every year.” Other influences can be environmental conditions such as temperature.

Where do they come from?

A tiny blackpoll warbler flies over the Atlantic from South America non-stop for four days and nights. The bobolink we see in the hayfield may have arrived from Argentina, and the turkey vultures soaring high over the Palisades were only recently in Central America. The fact that birds can travel this far to arrive at their breeding grounds truly is amazing.

Where can we see the migrants?

We are fortunate that we are located so close to the Mississippi Flyway, a major North American migration route (the others are the Central, Pacific and Atlantic Flyways). From local sites such as Spring Lake, Thomson and Blanding Landing, starting in late March and April, we can watch flocks of hundreds of American white pelicans arriving from South Florida on their way north. Dozens of other species of ducks and other waterfowl—northern pintails, American wigeons, grebes, loons—also pass through.

In May, we can see warblers, some of whom stay here to breed, along the Mississippi and at Palisades State Park. Scarlet tanagers make their home at Apple River Canyon State Park and Tapley Woods.

The Guardians explore many of these sites on our Thursday birding outings during migration season. These walks begin on March 22 and usually include trips to Lost Mound Refuge, recently declared an Important Bird Area, and to Green Island in Iowa. Please contact Barb Rutherford if you are interested in being added to the e-mail notification (see Notices).

A little further away, but worth the trip.

In addition to the Mississippi flyway areas, there are other great birding locations within a short drive of Jo Daviess County:

• The Magic Hedge is on the shores of Lake Michigan at Montrose Harbor, on the north side of Chicago. We have personally birded there and have seen 20 warbler species in one day. Information can be found at www.chicagoparkdistrict.com.
• Illinois Beach State Park is also on the shores of Lake Michigan in Zion, Illinois. The park has a varied habitat of beach, marsh, grassland and woods.
  Information can be found at dnr.state.il.us/lands/landmgt/parks.
• The Nachusa Grasslands in Franklin Grove, Illinois is a wonderful birding site and has as many as 180 species, including grasshopper and Henslow sparrows and dickcissels. Information can be found at http://www.nature.org
• Wyalusing State Park is in southwestern Wisconsin and boasts nesting red-shouldered hawks, Kentucky warblers, hooded warblers and cerulean warblers, among others. Information can be found at www.dnr.state.wius/org/land/parks.
• If you are willing to venture a little further, a great spot is Magee Marsh Wildlife Area (AKA Crane Creek) in Northwestern Ohio on the shores of Lake Erie. Around Mother’s Day, you may see eighty-five species in a day, including golden-winged warblers. Information can be found at http:www.daf.state.oh.us/parks/cranecrk.htm.

Further information on migration may be found in:

• Chu, Miyoko. Songbird Journeys: Four Seasons in the Lives of Migratory Birds (New York 2006) ISBN 0-8027-1468-4.
• The Handbook of Bird Biology, the Cornell Lab of Ornithology (2004) ISBN 0-938-02762-X.
• White, Mel. Guide to Birding Hotspots of the United States, National Geographic ISBN 0-7922-5483-X.

  — Pat Caine and Judith Wehrle