Saturday, January 30, 2010

Anhingas, oil glands, and corrugated tail feathers

Erika and I saw many Anhinga during our recent Florida trip.  Anhingas are also called snakebirds because of their habit of swimming with only their long necks above water.  (The word Anhinga comes from a Brazilian Indian word for devil bird.)
Before writing up this blog entry, I had always assumed that birds' oil glands water-proofed their feathers, and that the Anhinga's habit of habitually holding their wings out to dry might mean they might lack an oil gland.  I have learned, however, that oil glands do not water-proof feathers--ducks with their glands removed still have water-resistant feathers.  The water proofing is in the feather structure. (Cornell Lab of Ornithology Handbook of Bird Biology)
Anhinga feathers are less resistant to water than other birds such as cormorants, which allows Anhingas to do that neck-above-the-water swimming, with their bodies submerged.  But, compared to cormorants, they must spend more time drying themselves out.
Ornithologists are well aware of the transverse corrugations on Anhinga central tail feathers.  These can be seen on the tail of the Anhinga photographed above (click on the photo for a larger image).  I am unaware of similar structures on other birds (perhaps some hornbills?)  None of my sources suggest a reason for this structure. (Notice that this bird has speared what appears to be a sunfish, and that its head feathers are remarkably wet.)

Wednesday, January 27, 2010

Florida

When folks return from trips, I always ask what was the best bird they saw.  In January 2010, Erika and I traveled to Florida, where friends invited us to spend two weeks at their condo on Sanibel Island.  We had a wonderful trip, adding about 120 species to my 2010 bird list.  Ever since Audubon's time, Florida has been famous for the tameness of its birds.  There are fewer birds in Florida now, but many of them are remarkably tame--a bonanza for a photographer.  My ever-growing Picasa site, http://picasaweb.google.com/danerika/Florida, has many of the pictures we took.

So what was my favorite bird?  Has to be the Florida Scrub Jay, since this was my 713th "North American" bird sighting.  (North American is in quotes since I count my North American birds wherever I see them, even outside the continent.)  We found the Florida Scrub Jay in the Merritt Island National Wildlife Refuge, just north of Cape Canaveral.  We had unsuccessfully searched for the jay for a day and a half, when Erika suggested we try the "Scrub Jay Trail."  "Unlikely," I replied, "How can they know there will be Jays down that particular trail?"  But, sure enough, at the far point along the trail, this Florida Scrub Jay tamely awaited us.


Erika's favorite bird is probably the Limpkin, found by some local birders for us.  They took us right to the spot, just east of Fort Myers, and there they were, three of them.  We walked for about an hour, but upon our return the Limkins were nowhere to be found (although we did hear them wail from the swamp).  The Limpkin is a bird we first found in Ecuador, so it was not new for our list, but this was our first North American sighting.



We missed seeing any Sail Kites.  This species apparently disappeared from the Fort Myers region just before the recent Florida freeze.  Nobody knows exactly why.  The kite was common enough in early December.