Establishing and Defending Birds' Territories - Page 1

Walking along the seashore beach of Assateague Island, Maryland, in September, you find a solitary Sanderling feeding in the surf. It runs to the base of a receding wave, sticks its bill into the sand, then scurries away just in time to avoid the next crashing wave. Fifty yards up the beach you spy another. It repeats the same behavior, looking not too different from a windup toy. Beyond it there is another, and another beyond that one. Each bird is "alone" and each is separated from its neighbor by about the same distance. As you continue up the beach, each bird moves along in front of you, but just so far. Before it reaches the next bird, it stops, hesitates, and then flies in a wide circuit out over the waves, returning to the point you just passed. It is as if you never went by. If the next bird goes a bit too far, it transgresses the boundary of its neighbor's feeding territory, and there is suddenly a fight.

This illustrates extremes in the spacing behavior of common birds, Blackbirds flock, and Sanderlings defend territories. The bird world is full of both behaviors.