Avocets and Stilts—Avian Elegance on Formal Display

BIRD BRAINS: Inside the Strange Minds of Our Fine Feathered Friends (ISBN: 978-0-7267-8755-5)

by

Budd Titlow

http://www.buddtitlow.com

 

If the bird world scheduled a royal ballet, black-necked stilts and American avocets would be the principal dancers.

With their absurdly long legs, gracefully extended bills, and boldly patterned and colored plumage, these closely related birds are—without a doubt—North America’s most beautiful shorebirds and among the most striking birds on the planet. Plus their every movement as they glide through shallow wetlands seems choreographed by either George Balanchine or Jerome Robbins. Watching these birds feeding together in a coastal marsh makes you feel guilty that you’re not paying admission to support the artistry of their dancing.

Avian paleontologist Alexander Wetmore writes “. . . one can not help admiring the skillful and graceful way in which [stilts] wade about in water breast deep in search of their insect prey. The legs are much bent at each step, the foot is carefully raised and gently but firmly planted again at each long stride.”

In the United States, black-necked stilts are locally abundant along coastal areas of California through much of the interior of the western United States and along the Gulf of Mexico as far east as Florida. They are found primarily in estuarine, lacustrine, salt pond, and emergent wetland habitats. American avocets nest in marshes, prairie ponds, and shallow lakes in the Midwest and along the Pacific coast of North America while they spend the winter along both Atlantic and Pacific coasts of the United States.

Potential predators that assume these long-legged beauties can’t effectively defend themselves are always in for a big surprise. Both the stilt and the avocet have some amazing behaviors designed to ward off threats to their safety. The most impressive of these is the black-necked stilt’s “popcorn display” during which all the adult birds in a colony alternately hop up and down—like popping corn—while wildly flapping their wings and calling out loudly and incessantly at the offending intruders.

Avocets use a variety of defensive tactics such as loud screeching and “crippled bird” acts. When a nesting colony of avocets is threatened, non-nesting adults will rise in unison and begin a dive- bombing display, repeatedly swooping down on the predator until the intruder turns away. The attacking avocets also issue a series of call notes that gradually change pitch, simulating the Doppler effect and making the predator think they are approaching faster than they actually are.

Another clever distracting display used by both stilts and avocets is “false incubation,” during which an adult bird crouches on the ground—as if incubating eggs—then gets up, moves to another spot, and crouches again. In the process, potential predators are lured away from the real nests and eggs.

Because stilts and avocets are both wetland birds, they are vulnerable to runoff pollution, including pesticides and especially selenium. However in the continental US, populations of both of these birds appear to be stable or slightly increasing. This is very good news because it ensures that we may be treated to a command performance of the royal bird ballet anytime we approach a US coastal wetland.