Bird Notes
Bird Notes 1/10/08
Jan 10, 2008

A Turkey Vulture sunning itself: The technique may have many functions, but is probably largely used to warm up after a cold night. %u2014M. Jobling photo

Gary Trask of Cross River, N.Y., recently observed a spooky sight.

“While on my route as a package delivery person in South Salem, specifically on Waccabuc River Lane, I spotted about a dozen Turkey Vultures in seven, eight, or more trees, all with wings spread toward the 10 a.m. sun as if trying to melt the frost from the long night roost,” he writes, adding that it “looked like a scene from a horror movie.

“I have seen this done by cormorants, but this was amusing and a little eerie looking. Probably goes on all the time but a first for me.”

Indeed, it does happen often among vultures and a few other large-sized birds such as cormorants, anhingas, pelicans, and storks.

Gary had the right idea about what was going on, but ornithologists believe there may be more than just warming involved.

Both Turkey and Black Vultures can often be seen in the morning with their wings in what is called the “spread-wing posture.” This is a form of “sunning,” in which the birds open and angle their wings to get maximum exposure to the sun.

Certainly, warming up after a cold or cool night is probably the main reason for doing this. Vultures spend the night in roosts with lots of other vultures. They are big birds and, although they roost in evergreens, cannot really protect themselves much from exposure to the elements.

In winter, a Turkey Vulture’s temperature can drop overnight from a normal of around 99 to about 93 degrees. This can cause the bird to be sluggish. Spreading its wings in the morning will catch as many warming rays of the sun as possible so it can return to a normal temperature and function.

Scientists also suspect that sunning is used to dry up the dew that forms overnight on the birds. However, the benefits of sunning may be even more multifaceted.

While the technique certainly provides warming, it also reduces the need for food. The vulture is warming up using the sun’s energy instead of its own energy, which would be generated by burning calories. Calories come from food and sunning means that the bird needs to find less food to survive. And in the winter, locating carrion is not as easy as in other seasons.

Sunning may also help maintain the health of the feathers. Exposure to the sun may keep the feathers supple. It may also get rid of parasites that feed on the feathers. Exposure to the sun is said to drive the parasites to places where the bird can remove them by preening. Sunning may also stimulate the formation of vitamins.

There is yet another reason why vultures may use the spread-wing posture. “The possibility that birds might sun simply because it feels good is difficult to test,” writes George A. Clark Jr. in Handbook of Bird Biology.

Cormorants and anhingas spread their wings mostly to dry them after long dives in search of fish, but also to warm from the cooler water temperatures. For anhingas, drying is even more important than for comorants because they have less oil in their feathers, which makes them less buoyant. This helps the anhinga stay under water with ease for longer periods, but it also means it takes more time to dry their water-logged feathers.

The last time we saw a Turkey Vulture sunning was just after Thanksgiving. The bird had perched atop a chimney on a nearby house and spread those five-plus feet of wings for all to see. It was a pretty dramatic sight. And yes, it was eerie.

The house has a for-sale sign in front. Fortunately, no real estate agents drove up with a client.

Coming Up
Bald Eagle Survey at George’s Island Park, Montrose, on Hudson River, sponsored by Audubon New York, with Bedford Audubon volunteers, Sunday, Jan. 13, 3:30-5 p.m., no registration necessary, George’s Island Park, 199 Dutch Street, off Route 9A in Montrose.

Hike at Croton Point Park, looking for Bald Eagles, ducks, etc., with Tait Johansson, Wednesday, Jan. 16, 8:30 a.m., meet at Bylane Farm, 35 Todd Road, Katonah to carpool, Bedford Audubon, register  jebecker@bedfordaudubon.org or  (914) 232-4806.

Eagle Viewing Boats Tours, Feb. 9 to March 16, Tuesdays/Thursdays, 10 a.m., Saturdays and Sundays, 9 and 11, Connecticut Audubon Society, 860-767-0660, pwood@ctaudubon.org 

Eagle Festival, Feb 16 and 17, Connecticut Audubon, Essex, 860-767-0660

Bird walks with Luke Tiller, Saturdays at 8:30 a.m. $5 each; to register, www.sunrisebirding.com/walks.htm;  203-981-9924, luke.tiller@gmail.com.

First Sundays, birding at Greenwich Point with Meredith Sampson of Wild Wings, and other guides, Feb. 3, March 2, April 6, May 4, 9 a.m., meet at the second concession stand, 203-637-9822.

Bird walks, first and third Saturday at 7:45 a.m., free, meet at Wild Bird Center of Norwalk, 335 Westport Avenue (Route 1), www.wildbird.com/Norwalk, 203-846-BIRD.