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As the end of the summer draws near, many of you may be preparing for the return to school. Migratory birds are preparing for something, too–the return to their wintering grounds, in some cases many thousands of miles away. What is migration, and why do birds do it?  Migration, or movement from one place to another, is a common behavior in many animals, including birds, mammals, amphibians, fish, and even insects. One of the better-known migrants is the monarch butterfly, which moves between its wintering grounds in Mexico all the way north to Canada. Birds carry out this amazing feat, as well. The Arctic Tern, for example, makes a remarkable round-trip journey of over 20,000km each way, flying between the Arctic and the Antarctic. 

Arctic Tern/Photo by Kirk Rogers/FWS

Migration is one of the most dangerous things a bird can undertake. Migrating birds risk death from starvation, exposure, predation, and exhaustion. Collisions with radio towers and buildings are also proving to be dangerous migration barriers. So why do they do it? Birds appear to migrate to take advantage of more favorable conditions. Rather than migrating to escape harsh winters, birds make the move so they can get to the good stuff–food. During spring and summer months at higher latitudes, days are longer, giving birds more time to forage. The sheer size of the northern temperate zone allows for greater breeding dispersal–birds don’t have to crowd close to their neighbors to find a sufficient breeding spot. Once the breeding season ends, though, North American migrants move south as food becomes less abundant.

Red Knots/Photo by Greg Breese/FWS
Fall is a great time to see migrating birds. The Copper River Delta, in Alaska, the Delaware Bay in New Jersey and Delaware, Cape May, New Jersey, and Hawk Mountain Sanctuary, in Pennsylvania, for example, are world-renowned locations for observing the fall migration. Millions of shorebirds gather at the former two spots to refuel for the remainder of their trip south, while the latter two sites are famous for large numbers of migratory raptors, among other things.

At Hawk Mountain, the Kittatinny Ridge of the Appalachian Mountains funnels migrating raptors over the lookouts and surrounding peaks on their way to their wintering grounds in the south. On average nearly 18,000 raptors migrate through the area each year between August and December.

North Lookout at Hawk Mountain Sanctuary/Photo by Shawn Carey
Visiting a migration site like these can provide tremendous views of birds, and I definitely recommend it if you have the opportunity. But you don’t have to go to these spots to observe the fall migration. Your own backyard, a park near your house, or another area that provides good bird habitat can be just as effective (on a smaller scale, of course). Start early in the season. Take notes about which species you are seeing, what they are doing, and where you are seeing them. Continue this over the course of the fall. You may be surprised at what you can infer from your data at the end of the season. When do different species migrate?  Do males and females appear to migrate at the same time? How about young birds and adults?  Do certain species seem to migrate earlier or later than other species? Why do you think this is?  Pay close attention to the type of food that each bird eats. Does it become scarce? If so, are you still seeing the birds that feed on that source?  Why or why not?

Over time, keeping detailed notes in your field journal about what, where, and when you see birds in the fall can provide important insights into timing and length of migration. It will also help you know what to expect (and what is unusual) at your favorite birding spots.