Black-bellied Whistling Ducks & other migrants at WRL

[betsy]

Sunday 4/8 there were slews of swallows -- Purple Martins, Barn Swallows and Northern Rough-winged Swallows -- flitting about the lake in the late afternoon & evening, as well as a large raft of Northern Shovelers and the three Eared Grebes mentioned earlier.

Monday the shovelers were gone, and the number of swallows had greatly diminished and were primarily Purple Martins.

Jim Peterson's checklist of birds for WRL lists only one record of the appearance of Black-bellied Whistling Ducks at WRL. Here's another -- JR Compton photographed a pair at Sunset Bay Tuesday (4/10): http://www.jrcompton.com/photos/The_Birds/J/

[EastLawther]

Thanks for the tip. Went to see the black-bellied whistling ducks. The pictures in the field guides do not do this duck justice; that beak is fluorescent.

They're still there at sunset bay on thursday evening, april 12. As were the eared grebes, near arboretum. Maybe they'll hang around for the picnic on the 14th for everyone to see. ;)

[T. David Griffith]

Betsy, where and what is WRL? Thanks.

[betsy]

Oh! Sorry, David! That's shorthand for White Rock Lake. (Lake-banding code? ;) ) Which, you doubtless know, lies between Mockingbird Lane and Garland Road, west of Buckner Blvd. In Dallas. Some way east of I-75. Maps in the WRL forecast forum.

The Sunset Bay section is accessible by car from the Lake Highlands Blvd. entrance off of Buckner. You take the first left west of Buckner on Lake Highlands, take a left when that T's into another park road and follow it around until you get to the lake.


(Note: I just changed the name of the White Rock Lake Forecast forum to White Rock Lake (WRL) Forecast, so that it might be more obvious what is meant next time anyone uses that abbreviation. Hope that helps!)

[T. David Griffith]

Betsy, thanks. I kept trying to think of something for WRL. I guess I needed another cup of coffee this morning.

[Perry]

Eared Grebe - Yes
BB Whistling-duck - N

[Siva]

As I was driving along E. Lawther behind the Arboretum, I saw about 20 of what I believe are Ruddy ducks but I couldn't clearly distinguish the color of their bills - it was not as blue as what I see on some on-line pictures. The tails were clearly pointed up and wagging. Not so bright but clearly visible white cheek on the males. Are these Ruddy Ducks - have anyone seen these today?

Thanks.
Siva

[betsy]

Siva, the only small duck with its tail raised that you're likely to see on White Rock Lake in such quantities is the Ruddy Duck. The big white cheek patch on the males just confirms it. Even without having seen them myself, I can assure you that they were Ruddys.

The blue on the bills of the males may look more or less intense depending on the available light and the angle of view. Blue is almost always a structural color in creatures rather than a pigment, meaning that it's caused by the scattering of light from some structure or other. I wasn't sure if that applied to the bills of male Ruddys, but with a little research I discovered that it does -- in their case the light is scattered by "parallel, quasi-ordered arrays of dermal collagen fibers," as mentioned* in this article:

Bagnara, Joseph T., Fernandez, Philip J. & Fujii, Royozo (2007)
On the blue coloration of vertebrates
Pigment Cell Research 20 (1), 14-26.

(You can find this info in the section on "Blue colors of birds" at the link below:

http://www.blackwell-synergy.com/doi/full/10.1111/j.1600-0749.2006.00360.x

Note: You'll probably need to click on the "Full text HTML" ((or pdf)) link in the area at the far right under the bright green bar to get the entire article.)

* The original research was conducted and described by:

Prum, R.O., and Torres, R.H. (2003a). Structural colouration of avian skin: convergent evolution of coherently scattering dermal collagen arrays. J. Exp. Biol. 206, 2409–2429.


(Thanks for asking and thereby provoking me into finding this article! :) )

[Siva]

Thanks Betsy for the confirmation and the reference - interesting article.