On one of the first sunny, warm days this past April, a couple of visitors and I were watching two Spotted Sandpipers. The birds were foraging outside the Eastern Shore of Virginia National Wildlife Refuge Visitor Center observation window, merrily bobbing their tails as they gleaned insects from the grass. One of the visitors looked at me and asked the inevitable question, Why do they bob their tails?

This led to me wondering why many birds have strange behaviors. What purpose do these behaviors serve? For instance, everyone familiar with the Eastern Shore has observed Snowy Egrets running around the marsh edge wiggling their golden slippers. Why do they do that? If you observe them, you will notice after they wiggle their toes they catch a fish. One might wonder if there is scientific evidence to prove that this behavior assists in fish catching. Many studies have looked at the foraging behaviors of these birds, and they have concluded that they wiggle their toes to stir up the mud and flush fish closer to the surface. So, yes, this behavior does increase their foraging success.

What about other species? Cormorants sit on pilings with their wings out. This unique behavior amazes people as they walk around the two refuges and on Fisherman Island trips. But why? No other bird on the Shore does this.

Cormorants have oil glands which make their wings water proof like other water birds. So, you'd think they weren't holding up their wings to dry them in the sun, but they are. Their wing feathers do not shed water well. So, despite the fact they spread the waterproofing oil on these feathers when they preen, their wings still get waterlogged after deep dives. Hence, they perch and hold their wings out to dry.

Other birds, such as nuthatches and creepers, exhibit behaviors that may not be as easily explained. Brown Creepers feed by ascending a tree in a spiral or straight course. Once they reach the top of the tree, they drop and repeat the process on another tree. In contrast, nuthatches, such as the White-breasted Nuthatch, moves down a tree trunk when it forages. These two very different strategies produce the same effect. They both allow the birds to be successful in foraging. Why do they use two different behaviors? They may use different strategies to avoid competing for food, since they often are feeding on the same tree. The reasons are not as clear as with the egrets and cormorants.

This brings us to the question we started with, why do Spotted Sandpipers bob their tails? Some have suggested that their nodding and teetering helps them blend into the movement of the water edge and the light waves. Hence, a type of camouflage. However, even if we are not exactly sure why these birds have their particular unique behaviors, watching bird behavior can be fun.

So, next time you are at your favorite bird spot, take time to watch the birds, not just identify them. Who knows, you may unlock the mystery of the Spotted Sandpiper bob.

Sheila Faith
ESVNWR Outdoor Recreation Planner