By Bryan Stevens
September’s arrival puts fall migration into overdrive. The birds that returned this past spring — the warblers, vireos, tanagers, grosbeaks, flycatchers and hummingbirds — have begun or are beginning to make their way back to the locations where they will spend the winter months far from the cold, bleak conditions over most of North America.
Some of these birds migrate out of the tropics to avoid competition. Others find North America a land of abundant, albeit temporary, resources. This land of plenty offers a wealth of insects, seeds, fruit and other nourishing, nutritious food to help parent birds keep their strength while they work to ensure their young thrive. Of course, once the bountiful period concludes, they return to the tropics of Central and South America to winter. Those that do so successfully will make the journey back to the United States and Canada in the spring.
The phenomenon of migration isn’t exclusive to the neotropical migrants of the New World. Birds in other parts of the world migrate, too. Waterfowl, shorebirds and raptors are among some of the families of birds that stage impressive migrations.
The Arctic tern, for example, truly takes migration to extremes. This small seabird travels each year from its Arctic nesting grounds to the Antarctic region, where it spends the winter months. Put into terms of mileage, the Arctic tern can travel about 50,000 miles in a single year. For a bird with a body length of about 15 inches and a wingspan of about 28 inches, this incredible migration is an astonishing feat. These statistics permit the Arctic tern to easily lay claim to the title of champion migrant among our feathered friends.
According to the website for National Geographic, Arctic terns face a serious threat from climate change. In a profile on the tern at its website, National Geographic warns that Arctic terns are projected to lose 20 to 50 percent of their habitat due to the temperature changes linked to climate change. They also face loss of habitat due to encroachment by human activities such as oil drilling.
The ruby-throated hummingbird, a favorite of many bird enthusiasts living in the eastern United States, makes an impressive migration each year. Just to reach the United States, these tiny birds undertake a strenuous journey. They leave their wintering grounds in Central America to return to the United States and Canada for the nesting season. Most of these tiny birds, which are barely four inches long, make a non-stop flight of more than 500 miles across the Gulf of Mexico. The journey can take almost an entire day. With the end of summer, the entire population of ruby-throated hummingbirds, increased by a new generation of young birds, makes the Gulf crossing for a second time in a year to return to the American tropics for the winter months.
Among North America’s buteo hawks, which includes raptors such as red-shouldered hawk and red-tailed hawk, the broad-winged hawk stands out as a dedicated migrant. These hawks form flocks that at times number in the hundreds or thousands as they sail and glide on thermals rising over various mountain ranges. These hawks and other raptors are well-known in the region for migrating past the Mendota Fire Tower in Southwest Virginia every September and early October.
The broad-winged hawk’s counterpart in the western United States is Swainson’s hawk, which shares the broad-winged hawk’s inclination for migrating in large flocks. Swainson’s hawk is named for William John Swainson, the famous 19th century English naturalist for which Swainson’s thrush is also named.
The hooded warbler, my favorite member of the migratory New World warblers, migrates back to Mexico and Central America for the winter months after nesting during the spring and summer in a range concentrated in the southeastern United States. The males, after going quiet in late summer, have started singing on occasion from the shaded woods around my house. I think this has more to do with restlessness as they prepare for to depart on a migration flight that will take them to the balmy Caribbean, Mexico and Central America while we shiver through the months between October and April. It’s not a migration of an incredible distance, but it’s still quite an accomplishment for a bird only five inches long and weighing less than half an ounce.
Fall’s a great time to witness the variety of avian life. Look for some of these migrants passing through your yards, gardens or favorite birding spots.