Tuesday, August 12, 2008
The Bird that Walks on Water - Clark's and Western Grebe
Perhaps running on water might be a more appropriate term for part of the captivating courtship ritual of these two closely related, fascinating species. Not considered ducks, geese, or even waterfowl, these less commonly observed birds are considered just “waterbirds”, a somewhat ignominious term given their spectacular breeding season displays considered to be among the most complex known in birds. Those of you lucky enough to have witnessed the event will likely always remember it. Certainly, it is frequently shown on television nature shows. After a series of calls and posturing, the pair rises up on their feet, and with wings beating furiously, literally run across the surface of the water. A second ritual, “the weed ceremony” cements the pair bond. Beginning like the prior example, a weed dancing couple simultaneously dive to the lake bottom to gather a mouthful of vegetation, rise to the surface, and then rise on the their feet while holding the vegetation bill-to-bill.
Clark’s and Western Grebes are remarkably similar in appearance, with only subtle differences in facial pattern, bill color, and calls to differentiate the birds to our human eye. In fact, the two are so similar that from 1886 to 1985 they were considered to be one species. Highly social, they can be found on our larger lakes, particularly those with the marshy vegetation necessary for nesting during the spring. During winter, on open water, they may be found in large rafts of both species, where they hunt mainly for small fish and other aquatic animals, which are usually swallowed underwater, a seemingly impossible, if not illogical feat. Furthermore, each individual can consume up to a pound of fish a day, so large groups are capable of quickly depleting the food resources in a small pond or lake.
Superbly designed to efficiently ‘fly’ underwater, grebes have short wings and feet and legs that are positioned near the rear of their bodies, making them ungainly on land. In fact, most grebes rarely set foot on terra firma, except during the nesting process. Grebes almost never fly except during migration which occurs at night. Additionally, grebes, replace most of their feathers all at one time, rendering them flightless for much of their nesting period. This effectively restricts their range to the pond or lake that they selected for their nest site, and subjects the pair and their young to the perils of uncertain weather, water levels, and adequate food supplies.
Nestling grebes are able to swim and dive within 24 hours of birth, but are not terribly water-proof. Like loons, a closely related species, young grebes spend most of their early weeks riding on the backs of their parents. At this time of year, young grebes are independent of their parents and might be found in close company with others of their kind. Check out the lakes of New Mexico for a look are these rare and interesting birds! If you’re lucky you might even see the dance!