Monday, May 11, 2009

A Family Affair: American Avocet

American Avocet. Photo by David Powell

The two American Avocets stood, silent but alert, in the shallows of a New Mexico wetland. Brilliant slivers of crimson in the eastern sky heralded the onset of the day. The female had been assiduous in her companionship, and eventually the male accepted her presence. Now, the two were rarely far from one another. Like a pair of ballet dancers, the birds were the epitome of elegance with their striking feathers and graceful, upturned bills, the silhouette of their image reflected in the mirror of the glassy surface of the water.

The dance began when the female slowly and deliberately leaned forward, stretching her neck as far as possible, submerging her bill into the water. This was the cue for the male to begin his solo performance. He began to preen his feathers on the side nearest his mate, dipping his bill into the water and lifting it to his breast. With the second dip, he shook his bill splashing water on the pair. He continued, moving in an ever increasing frenzy of vigorous splashing, until he joined the still motionless female, and they became one. After, in the grande finale of their ritualized dance, the pair stood side by side with necks intertwined, and ran as one through the shallows.

Avocets prefer to nest on islands within a wetland, if possible, because it provides some protection from predators. Their nest-search, which also is part of the pair formation, includes ritualized scraping displays. The final nest site often is somewhat elevated with a clear view from which the pair can scan for predators. Sometimes, females lay eggs in the nest of another female, who then incubates the eggs. Avocet eggs have been found in the nests of other species too, such as gulls. Likewise, eggs of other species sometimes are found in avocet nests. So, an avocet parent might raise a mixed species family that could include Black-necked Stilts or even terns.

Modern day parenting is the norm, where both parents take turns incubating the average size clutch of four eggs. Early on, the male performs on the bulk of incubation. In warmer areas, with relentless sun baking the sandy shores, incubation consists of cooling, rather than warming, the eggs. Parents soak their belly feathers before sitting on the nest. Evaporative cooling prevents the eggs from getting too warm.

For a vulnerable chick, life on the edge of a wetland is precarious. Young are up and out of the nest within 24 hours. Day old chicks can already walk, swim, and dive. Older, but still flightless, chicks can dive and swim up to 21 feet underwater using their wings and feet. If the nest is on an island, chicks follow their parents and swim to the shore, where they are raised in a nursery area with shallow water and dense vegetation for cover. Often, several avocet pairs will cooperatively raise their young in a communal nursery. Here, the chicks might a brooded by different parents.

Often, female parents abandon the nursery before the young a fully independent, leaving the remainder of the care with the males. Maybe, just maybe this is part of the reason why he is reluctant to initiate courtship, knowing what his parenting duties will be, and why avocets rarely have the same mate the following season.

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