Migration

Scissor-tailed Flycatcher (Tyrannus forficatus). Near Pampa, Texas; 25 September 2011

Migration is a fascinating thing.

Most people only think of birds as the animals that migrate, and only certain species of birds. But in nearly every other major group of animals, there is a species that migrates. Among mammals, there are the mass migrations of the large mammals across the African Savannahs. Some reptiles migrate, such as when sea turtles swim across an ocean to breed on a beach. Some amphibians migrate, such as certain salamanders crawling along the ground to a breeding pool. And certain fish migrate, such as tuna and sharks.

But birds are perhaps the most visible migrants we see, since we can hear their songs, see them in our yards, and some are seen in vast numbers like geese. The traditional migrants people think of are geese, in their long V-shaped lines, and ducks.

Though you see American Robins (Turdus migratorius) year round in some areas, they do migrate! In the United States, the robins you see in winter in New York, Missouri, and other states are not the same you see in the summer! Robins that breed in the far north in Canada and Alaska are perfectly happy in places like New York for the winter; while the birds that breed in New York in the summer fly south and spend the winter in less harsh conditions, such as in Missouri, Texas, or even as far south as Mexico.

Other less commonly known migratory birds are ptarmigans. Being a "grouse-like" bird (chicken like), they are not strong fliers. However, they will migrate short distances, up and down mountain sides corresponding to the seasons, to take advantage of the best food sources.

By far the most abundant groups of migrating birds are those that are inconspicuous to the layperson. As a whole, they are referred to as the "neotropical" or "nearctic" migrants. These are the wood-warblers, the tyrant flycatchers, the thrushes, the vireos, and the new world sparrows, among others. In the fall, well over a billion of these individuals take to the air, and go south. Some go only as far as places in Mexico; most fly to the forests of central America; and a few species will go as far as places in South America.

Think of that - over a billion animals, all with a common purpose: move south.

Now REALLY think about migration for a moment. You can't really "see it", unless you happen to be able to fly an ultralight aircraft and can follow a bird. For most people, they don't even think about migration, until they realize some of their less common backyard birds are gone, or they start to see geese overhead.

I have had the privilege of working a few different jobs where I had the opportunity to "see" migration in a way, including my current one in the Texas panhandle. The way I "see" migration in these cases is by being in the same location, day after day after day, and being outside watching the birds. In southern California in 2008, I conducted feeding observations of birds. I could actually watch how a bird refueled itself for its next flight. Just one of many behaviors I watched (and still watch) that are a part of migration.

Both there in California, and here in Texas, I see migration by the "changing of the species." Over time, the makeup of the bird species I see each day changes, until the birds I saw at the start of the season are no longer present, and new birds have taken their place.

For example, at the start of my time here in Texas, we had a decent variety of birds around. We had Barn Swallows, Cliff Swallows, Scissor-tailed Flycatchers, and both Eastern and Western Kingbirds, among other species. Over the course of a few weeks, we began to see fewer and fewer of these species, and see more and more Horned Larks and both Eastern and Western Meadowlarks, as well as Lark Buntings. Currently, we are slowly increasing our numbers of Field Sparrows, Song Sparrows, and Savannah Sparrows as well. Our most vocal birds, though, are the Sandhill Cranes, which arrived here from the arctic a few weeks ago, and will stay for the winter.

While in Austin this past spring, I also saw the migration occur, in a more limited way. The warblers and vireos trickled through during the months of April and May, bringing some variety to my local bird life. It took a fine ear to make sure that when I was following a chip note, that I was following my breeding species, not a migrant. Learning the chip notes was also a good way for me to find birds when I was leisure birding. And I found my Bay-breasted Warbler this past year that way.

Those small songbirds invest a lot in migration.

These are some powerful birds! A bird such as the Blackpoll Warbler, which is not even 6 inches long, will DOUBLE its weight from around 10 grams (the weight of 4 pennies) to over 20 grams in the fall. Breeding in the boreal forests in the north, it fattens itself up as it slowly makes its way to the east coast, and a little south. Then, when fully fattened, and having the right weather conditions, they take off. Flying a little east and then turning south, they fly non stop from the mid-Atlantic coast (Virginia, Maryland, Delaware, New Jersey area) to South America, a journey of over 2,000 miles over about 80 hours. All under their own power.

Really think about that. No landfall. Three days, three nights. No radar to tell them where a storm is. No GPS to tell them where they are. No landmarks for miles on end. If they aren't fat enough, they die. If they get tired and stop flapping, they die. If they hit a storm front, the journey becomes longer, and they may die.

Fascinating stuff.

Even more incredible? That the hummingbirds migrate too! A bird that weighs about 3 grams - just over the weight of a penny - will fly non-stop over the gulf of Mexico to get to it's winter grounds. That flight takes longer than a day. And once again, no radar to warn of storms, no GPS to tell it where it is, and no food on the journey.

Also incredible about this? In the fall, nearly 75% of the birds flying south have NEVER done that before. These are the birds that hatched that year. And they don't get taught, they don't get apprenticed. Pure instincts drive them south.

And to top all that - they do it again, in reverse, in the spring. And since most of these birds will live from 4-8 years (longer in larger species), they do it again. And again. And again.

Wow.

Makes you look at your backyard birds a little differently, huh?