Monday, November 7, 2011

An anhinga discovers Bare Lake

An anhinga spreads its wings wide to dry in the breeze

Simply Living
November 7, 2011

An anhinga has taken a liking to our lake. It arrives in the morning and spends the day either in the water fishing or perched nearby drying its wings.

Anhingas differ from most water birds in that they don't have oil glands to waterproof their feathers. Unlike ducks that can dive under water and return to the surface, the anhinga must air-dry its feathers after each submersion. The bird in our lake re-fluffs its feathers in various locations. Sometimes it sits atop the mid-lake platform, while other times it stands on a partly submerged log, on the uppermost canes of bamboo or even on the arms of a plastic chair on our beach.

"Come see this bird by the beach!" my husband called from the porch.

"It's an anhinga," I said when I joined him outside. "Or a cormorant — I'm not sure which."

Because the two birds look very much alike and have overlapping habitats, they are often mistaken for each other. Both are large, dark-colored water birds without oil glands that swim through the water with only their heads exposed and spend extended periods perched along waterways air-drying their broad, outstretched wings.

Although there are several noticeable differences between the two fish-eating predators, the easiest way to determine which bird is which is to focus on the neck and bill. If you are looking at a slender, long-necked bird with a straight, pointy beak, it's probably an anhinga. However, if the bird you see has a shorter neck with a curved, hooklike bill, it is most likely a cormorant. Cormorants also have a distinctive orange throat pouch as well as a stockier body and shorter tail feathers than anhingas.

Despite those differences, I still get confused. I've found the easiest way to distinguish between the two is to think of the anhinga's nickname, snakebird. Since the anhinga's neck is so long, it is sometimes mistaken for a snake.

Anhingas and cormorants share similar diets, but their methods of catching food differ. The cormorant uses its hook-shaped, serrated-edge beak to grasp slippery prey, while the anhinga impales its catch on its long, pointy bill. Once prey is caught, the cormorant will eat under water while the anhinga tends to devour its meal on land by tossing it into the air and swallowing it whole. Occasionally a fish will be so severely speared that the anhinga will have to ease it off its beak by rubbing against a hard object.

I haven't watched the anhinga in our lake devour any fish, but I have seen it dive off its perch in search of food. The main time I notice this 3-foot-tall water bird is when its 48-inch long wings are open to catch the breeze.

"It really seems to like that plastic chair," my husband said as we stood outside watching the bird watch us while it air-dried its wings.

"I thought it would mind us being so close but it doesn't seem scared," I said as we eased closer to get a better look.

The bird didn't have much choice but to wait patiently for us to go away. An anhinga with wet wings has difficulty flying. It can do little more than skip along the water's surface while madly flapping its wings.

"I'm glad it's here," I said, when we returned to the house. "I like looking out and seeing it on the perch. It's a weird- looking bird, especially with its wings outstretched, but also exotic."

Herons, ibises, wood storks, egrets, rails, grebes, ospreys, hawks, various ducks and the occasional eagle have all made their appearance on our lake at one time or another. Some are regulars while others come and go with the seasons. Whether the anhinga is an occasional visitor or takes up residency matters little. Every bird is a welcome addition.

I recently received an email from an Everglades National Park volunteer with some relevant information about anhingas.  Here's his email in full:

I recently read one of your 2011 articles on Anhingas, and felt an
irresistible urge to correct an error of fact. Anhingas do have
uropygial or preening oil glands. Their wing and tail feathers are
fully waterproofed contrary to Audubon and most other sources, even
reputable ones. Please see photos (1st one not mine) showing gland and
preening. Another way to prove this is to take a feather, dip it it
water, remove, perform a couple of Flitwickian swishes and slicks, and
you will be hard put to to wring even a small droplet of water.

I have had to suffer an education about blindly accepting "facts" from
authoritative sources on nature. As an Everglades National Park
volunteer whose job includes interpreting wildlife for visitors, I now
check everything with judicious observation and with experienced
colleagues. I preface what I say with "I have read that..." or "we
think that...." Only when I have verified something by observation and
concentrated research can I claim something is true. And even then, I
suspect that half of what I say is wrong.

Meant in a friendly way....

Chris Reiss

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