Fall Bird Migration Is in Full Swing
Friends of Dyke Marsh learn facts and hazards of migration.
It may seem quiet outside these late summer nights, but there’s a lot going on in the skies. Millions of birds are migrating south day and night.
On Wednesday night, 75 people turned out to hear Alicia King of the U.S.
Fish and Wildlife Service’s Migratory Bird Program offer insights into the
mysteries of bird migration. The program was sponsored by the Friends of Dyke Marsh and the Audubon Society of Northern Virginia.
The Mount Vernon area is prime territory for the fall and spring migration because of the diversity of habitat, from wetlands to woodlands to the river. In mid-September, the numbers of neotropical species and dabbling ducks traveling through are on the rise. Shorebirds have been passing through since August.
Migration is the predictable movement of an animal from one location and climate to another location and climate, King explained, usually for resources needed to survive. Warblers, for example, fly to Central and South America in the fall because their primary food sources, insects, are there.
King told the group that there are both short and long-distance migrants. More than 300 bird species migrate, and almost half of those that nest in the United States and Canada are migratory. During migration, birds fly an average of 15 to 45 miles per hour. Most migratory birds fly between 2,000 feet and 3,000 feet above sea level; others fly as low as 500 feet and some as high as 20,000 feet above sea level. The longest migrations are more than 24,000 miles round trip per year.
Bird species like warblers, thrushes and sparrows migrate at night. Storks, pelicans, kingbirds, swallows and blackbirds are among those that travel during the day.
King showed maps of the four major flyways or migration routes: Pacific, Central, Mississippi and Atlantic.
How do they migrate? King said they have three techniques: (1) piloting, following landmarks like mountains; (2) orientation, using the sun, stars and earth's magnetic field as compasses; and (3) navigation, determining their position relative to the position of their destination.
Along the migration path, birds encounter many obstacles, King stressed. They crash into the windows of buildings and homes, especially those with lights on. Birds get confused by lights on communication towers. Outdoor cats are a “huge hazard,” she said.
What can people do to help birds? King urged putting silhouettes in windows so birds “can see something there.” She promoted purchasing only shade-grown coffee because coffee trees in Central America wintering grounds provide habitat.
And she encouraged pet owners to keep cats indoors.
One attendee asked how this year’s drought has affected birds. Negatively, she said, in short. Prairie “potholes,” shallow ponds and wetlands that have traditionally been migratory stopover points, may have dried up.
Mount Vernon resident John Perry asked how climate change is affecting birds. King responded that scientists "see a correlation between climate change and the timing of migration."
She gave as one example of climate change impacts the arrival times of ducks, saying that some hunters are observing that ducks are not in expected places at the same time as in previous years. And food sources like insects could be out of sync with birds’ arrival times.
The Friends of Dyke Marsh sponsors a bird walk at 8 a.m. every Sunday. The next members’ meeting will be at 7:30 p.m. Nov. 14 at the Huntley Meadows Park Visitor Center. Matthew Virta of the U.S. National Park Service will explore the human history of Dyke Marsh, from vice to farming to dredging.