Mystery bird: African darter, Anhinga rufa

African darter, Anhinga rufa, also known as the snakebird, photographed at Beseka Lake, Ethiopia (Africa).

Image: Dan Logen, 30 January 2011 [velociraptorize].
Nikon D300s, 600 mm lens, ISO 500, f/6.3, 1/800 sec.

Question: This Ethiopian mystery bird is closely related to three other species that live on three continents. Can you name this species and the three continents that its cousins are found on? For extra smug points, can you name those cousins?

Response: This is an adult African darter, Anhinga rufa. Some authorities place this bird into the family, Anhingidae, whilst others classify them into the same family with cormorants (shags), Phalacrocoracidae. It is thought that darters and cormorants are sister taxa because they have very similar morphologies and behaviours, but these taxa can be readily distinguished by their beak shape: all darters have a long, slender, sharply pointed beak with serrated edges.

In total, there are four species of Anhingas, all closely related: the Anhinga or American darter, A. anhinga, the Australian or Australasian darter, A. novaehollandiae and the Oriental or Indian darter, A. melanogaster. The three Old World darters are sometimes lumped together as subspecies within A. melanogaster.

Some of you were mislead by this bird's kinked neck, which is the result of convergent evolution -- a situation where function defines form. Both darters and herons have an s-shaped kink in their necks that facilitates their ability to catch prey. That kink allows the bird to snap its head forward with lightning speed so they can stab fish with that sharp beak. This s-shape is supported by morphological specialisations to the structure of the vertebrae and musculature of the neck. It also gives these species the ability to confuse bird watchers because they fly with their necks kinked, as you see in the image above.

You are invited to review all of the daily mystery birds by going to their dedicated graphic index page.

If you have bird images, video or mp3 files that you'd like to share with a large and (mostly) appreciative international audience here at The Guardian, feel free to contact me to learn more.

.

email: grrlscientist@gmail.com
twitter: @GrrlScientist