Thursday, January 17, 2013

The silver feathers on an Anhinga's's got bling!

When you seen Anhingas at a distance, they appear black, and you might not even know they carry a spectacular pattern of black and white (silver) feathers on their wings. When you're sitting right next to them, however, it's easy to see the "bling" on their backs...

A male Anhinga preening, showing off the striking pattern of black and silvery-white feathers on his wings.
This is the same Anhinga I talked about in two earlier posts that sat very close to me (click here for those close-up photos). Close viewing of the Anhinga's back let me study the beautiful pattern in his wing feathers (coverts and scapulars). I always thought these feathers were white, but up close, I could see they were silver...not white, not dull gray, but shiny silver!

The "white" covert and scapular feathers on an Anhinga are a glossy silver color. From a distance they appear white because of the contrast with the black feathers.
When I got home, I looked up Anhingas to see if they really did have glossy silver wing coverts and scapulars, or had I just imagined it. It turns out they do, and they owe their silver feathers to a special structure in the barbules of the feather. I found a detailed technical article published in the Journal of Morphology that explains why those feathers are indeed silver. Click here to read "Proximate Bases of Silver Color in Anhinga (Anhinga anhinga) Feathers," by Matthew D. Shawkey, Rafael Maia, and Liliana D'Alba.

...whether silver or white, the pattern on the back of an Anhinga is striking.
Bird feathers contain a center shaft called a rachis. Barbs branch off the rachis, and barbules branch off the barbs. The barbules run almost parallel with the rachis and hook together to make the feather strong.  The barbules in silver feathers are different--they are longer than those in other feathers, and they are flattened. Additionally, they twist a little, and one side is black and the other side is translucent. The twist means part of the translucent barbule is exposed, which creates the silver sheen. I found an article on the BBC Earth News site explaining the research of Dr. Ismael Galvan by Matt Walker called "Birds unveil 'silver wings'" (click here). This article is a little easier to understand than the technical research paper and clearly explains how the silver sheen appears on the feathers.

Galvan concluded that dark-colored birds evolved the silver sheen as a way to "become more colorful and conspicuous," while still keeping the benefits of dark-colored feathers (dark feathers contain the pigment melanin, which makes them stronger and protects the feathers from abrasion and UV radiation). 

This is the third part of the Anhinga series:
Part 1: Anhinga close-ups
Part 2: More Anhinga photos; spread-wing posture
Part 3: The silver feathers on an Anhinga's wings

Sunday, January 6, 2013

A little creeper in our backyard...

Our recent snows brought a new visitor to our backyard...a Brown Creeper (Certhia americana)! This cute mouse-like brown bird landed at the base of our half-dead weeping willow tree when I was standing about 20 feet away photographing Dark-eyed Juncos (click here for those shots). He efficiently and thoroughly worked his way up the tree, turning over loose bark and peering into crevices as he hunted out spiders and other overwintering insects and eggs. When he exhausted the willow tree, he flew over to the ash tree and worked his way up it...

Brown Creeper (Certhia americana) climbing up a Weeping Willow Tree in our backyard.
A Brown Creeper clings to the bark on the weeping willow tree in our back yard.

Brown Creeper (Certhia americana) using its tail as a prop.
I noticed the Brown Creeper was using his tail as a prop, much like a woodpecker does. 

That's a mighty fine pygostyle you've got there...
I recently read in the book Wild Bird Guides: Downy Woodpecker by Gary Ritchison, that the anatomical structure that allows woodpeckers to use their tails as props is called a "pygostyle." A cool name that stuck with me, because when I saw the Brown Creeper using its tail in the same posture, "pygostyle" popped in my head, and I wondered if a Brown Creeper's pygostyle was similar to a woodpecker's. After looking in a few books and doing a few Internet searches, I found it was.

How is it different?
The pygostyle in a bird is made from 4-10 fused posterior caudal vertebrae...basically, it's the bird's tail bone (like our coccyx). The pygostyle and the muscles around it give support to the tail feathers (rectrices), and while all birds have a pygostyle, not all pygostyles are the same. For example, the bones in a woodpecker's and creeper's pygostyle are much larger and the muscles surrounding it are much stronger than those in an average bird's tail. Most birds fly and perch on branches, but woodpeckers and creepers cling to and walk up the vertical surface of a tree trunk. Their tails help them stay in place because they work like a prop. Additionally, these types of birds have the adaptation of very stiff tail feathers, especially the middle feathers...all the better to lean on when clinging to or walking up a tree trunk. If you look closely, the middle feathers are also pointed and curve slightly inward to guarantee the tail makes solid contact with the bark (Ritchison, pg. 10).

Other birds have well-developed pygostyles too, for example, woodland hawks that use their tail feathers for precise steering through branches have well-developed pygostyles, and birds that use their tails for upward lift to help them hover, such as kestrels, do too.  If you'd like to see a labeled bird skeleton of the pygostyle, click here and look at #2. (However, if you've ever dressed a turkey or a chicken, you've already seen the pygostyle! It's the "Pope's nose" or the "parson's nose," the colloquialisms for the fleshy triangle at the tail.)

Brown Creeper (Certhia americana) checks out an abandoned woodpeckers hole.
While spiraling up the tree, our little Brown Creeper popped into an exposed and abandoned woodpecker's hole for a few seconds before continuing on. It's unusual to see a Brown Creeper standing out so well. Usually their camouflaging colors and patterns make them invisible against the bark. They are no match for the inside of a tree!

Brown Creeper using its tail to help it stay on the tree.
It's easy to see how the Brown Creeper makes good use of its tail. The pointed tail feathers are stiff like a Downy Woodpecker's and when combined with the strength of a well-developed pygostyle and muscles it becomes a very good prop and helps the bird cling to the tree trunk's vertical surface. 

This little brown bird is often hard to spot, and is often described as being a small piece of moving bark!
It's always fun to spot a Brown Creeper. They blend into the bark so well sometimes it's hard to see them. I usually hear their ultra-fine peeping and then watch until I see a little movement. Their habit of spiraling up a tree and then diving down to the base of the next tree helps a little when looking for one. 

...just like woodpeckers, this bird has evolved a well-developed pygostyle, stiff tail feathers, and inward curving tail feathers to help it cling to vertical surfaces. you can see the inward curve on the Brown Creeper's middle tail feathers. 

Closeup of the extra-long hind claw or back toe nail on a Brown Creeper.
...another adaptation, Brown Creepers have extra long back toe nails, or hind claws, to help them hook into the bark. 

The snow blew in another backyard favorite, our American Tree Sparrows (Spizella arborea)! Every year I wait for them to show up, but they never seem to arrive until snow or a severe cold snap moves in. I saw two on Wednesday....exciting. I love the tinkling, sweet calls of a flock of American Tree Sparrows.  This afternoon Rick and I went to Armleder Park to look for longspurs, we didn't see those, but we did see and hear hundreds of American Tree Sparrows...what a magical sound!
Click here for an older post on American Tree Sparrows--a favorite winter visitor.

Thursday, January 3, 2013

Ol' Blue is at it again...

While Red sits in the snow eating sunflower seeds, Ol' Blue continues to work hard to get me to change the name of the blog. "Blue and the Peanut is much more appropriate," says he…over and over…

Blue Jay pulling peanuts out of the peanut feeder.
"Blue and the Peanut!"

Blue Jay pulling peanuts out of the peanut feeder.
"Blue and the Peanut!"

Northern Cardinal eating sunflower seeds...and keeping an eye on me on the other side of the window!
"...mmmmmm, sunflower seeds!"

Northern Cardinal eating sunflower seeds...and keeping an eye on me on the other side of the window!
"...mmmmmm, sunflower seeds!"

Northern Cardinal eating sunflower seeds...and keeping an eye on me on the other side of the window!
"...mmmmmm, sunflower seeds!"
I'm starting to think he might be right...

Tuesday, January 1, 2013

Our snow birds are happy...

...because we have snow! What a perfect way to start the new year. It seems the persimmon seeds we cracked open this autumn were right...

A Dark-eyed Junco (Junco hyemalis) in the snow...the first bird of 2013!
A Dark-eyed Junco (Junco hyemalis) in the snow...the first bird of 2013!
I took these photos a few days ago when the snow first fell, but they fit perfectly with today's post because a Dark-eyed Junco was the first bird Rick and I saw this morning. Three little junkies were hopping on the deck, eating seeds I scattered last night.

A male Dark-eyed Junco sitting in a young mulberry tree as snow falls softly.
A male Dark-eyed Junco sitting in a young mulberry tree as snow falls softly.

...after rooting for seeds in the snow, this little female comes up with a snootful!
A female Dark-eyed Junco with a bill full of snow!

A sweet female Dark-eyed Junco roots in the snow for seeds.
...a snow bird on a snowy day.

Wishing everyone a Happy New Year!
...and all the best for 2013!

...for past First Bird of the Year posts, click here.