Bird migration is an interesting phenomenon. Some bird movements are subtle, such as the arrival of dark-eyed Juncos in fall and their departure in spring, but occasionally bird migration can be a newspaper’s shocking front-page story, such as occurred on Nov. 2, 1965.
On that day, a severe blizzard in Canada and the northern Great Plains must have blown every duck, goose and songbird south and into the Midwest. The sky was so full of migrating birds that the air traffic control radar systems in Omaha, Kansas City and Des Moines were overwhelmed and had to be shut down. Ornithologist estimated that 60 million to 80 million birds were in the air that day, flying south to warmer weather.
On the Audubon fieldtrip of March 8 this year, I was reminded of an event that occurred in 1965. We were at Saylorville Lake and saw thousands of geese in the air — Canada geese, snow geese and white-fronted geese. The white-fronted geese stole the show. I never saw so many of them in one day. They moved across the sky in the classic V-shaped skeins that did not seem to end.
Spring is the most spectacular migrating time, particularly the first few weeks of May in Iowa. It seems as if the birds are in rush north to establish their territory and to claim the best breeding and feeding areas.
The fall migration is more subtle. It starts in August and goes until mid-December as the birds work their way south. They move a little slower during the fall migration.
The reasons birds migrate and how they are able to fly thousands of miles is not completely understood by ornithologists. Most agree, however, that the main trigger that starts the migration phenomena is the changes of the length of daylight hours.
Scientists are hoping the new Montrus Wildlife Tracking System that has been installed across the state by the Iowa Department of Natural Resources will help to give us information about bird migration.
Birds might have begun to develop their patterns of migration during the last ice age as the glaciers advanced and retreated. The birds had to move south to look for food as the winter froze the northern landscape, and then in spring they had to fly north again to look for suitable nesting grounds.
Some birds migrate thousands of miles. The long-distance champion is the Arctic tern. It must journey twice a year from pole to pole — a round-trip flight of more than 20,000 miles.
The American robin, in contrast, only moves a few hundred of miles from the southern part of the U.S. to the northern sections of the Midwest and central Canada. Robins travel at the rate of 30 miles a day.
The common blue-winged teal is a faster flyer. It has been recorded flying 122 miles in one day along its migration route.
Scientists are studying the ways birds navigate on their long journeys, and experiments indicate birds use a variety of methods. Some use the sun if they migrate during the day. Others use the stars at night to find their way. It has also been proven that some birds have a type of internal compass and use the Earth’s magnetic field to navigate.
Another puzzle science is trying to solve regards the changing migration patterns and the range expansion of some birds. For example, some Canada geese are remaining in Iowa all winter if there is open water, and the young of these geese don’t migrate.
But other geese continue to have normal migration patterns. There are several species of birds, such as the cardinal, titmouse and great-tailed grackle, that are expanding their ranges slowly north and establishing residences in places where they did not normally live.
Many scientists think this might be due to evolutionary change in the birds’ genes, while others believe it is happening because of climate change. Climate change might be the reason we are seeing more American robins remaining in Iowa through the winter months as our winters are becoming warmer.
I saw some birds in Iowa this winter that are supposed to be father south in January and February. At Saylorville Lake in early February, I saw two great blue herons and a flock of 10 white pelicans feeding in the open water below the dam.
I also observed a male and female belted kingfishers feeding in the open waters of the Raccoon River west of Perry. These species typically migrate. Maybe these birds forgot that they are supposed to go south for the winter, but if birds can find food and have shelter, they don’t have to migrate.
Regardless of the reason, bird migration is one of the more interesting phenomena of nature, and ornithologists are trying to find explanations to the wide variety of behavior that birds exhibit during migration.
