Archive for the 'Bird Anatomy' Category

Aug 18 2015

Small and Belligerent

Male ruby-throated hummingbird in bander's hand (photo by Kate St.John)

Male ruby-throated hummingbird in bander’s hand (bander Bob Mulvihill, photo by Kate St.John)

Now that the breeding season is over and dry weather is suppressing native flowers, ruby-throated hummingbirds are swarming to backyard feeders in Pennsylvania.  All of them are small and feisty, but did you know the males are even smaller and more belligerent than the females?

Ruby-throated hummingbirds are sexually dimorphic in size though they’re all so tiny that only a bander could know.  At banding, birds are weighed and measured and so we’ve learned that male ruby-throats are about 87% the size of females in wing length and weight(*).  Their size is related to their lifestyle.

Female ruby-throated hummingbird in bander's hand (photo by Kate St.John)

Female (or is this an immature?) ruby-throated hummingbird in bander’s hand (bander Bob Mulvihill, photo by Kate St.John)

Male hummingbirds are the original deadbeat dads.  Ruby-throated males rush north in the spring to claim territories with lots of food which they vigorously defend with aerial displays, chasing, and bill-to-bill sword battles.

When a female shows up the male doesn’t welcome her at first (he acts annoyed) but he switches to intensive courtship displays when she perches.  Good hovering technique really impresses her and to do it well he needs lots of energy, smaller wings, and a lighter body than hers — which he has.

As soon as he’s mated with one lady he looks for the next.  He never helps with nesting and young and is so focused on attracting another female and warding off other males that he may forego feeding for much of the day.  Banders have found that adult males lose weight in June and July, though they regain it in August.

By the end of the breeding season there are noticeably fewer adult males than females at bird banding stations.  In a study done at Powdermill Nature Reserve, Bob Mulvihill and Bob Leberman found that the adult sex ratio is most skewed in the fall when there are 4.1 adult females for every 1 adult male.

Their paper(*), published in The Condor in 1992, describes why more adult males die in the summer than at other times of year:

“As a species, the Ruby-throated Hummingbird is near the extreme of small size that is physiologically possible for an endothermic vertebrate. It is conceivable that males approach a critical body mass during the summer.  Below this critical mass they may have to abandon nocturnal homeothermy for hypothermic torpor, and may starve overnight or during periods of inclement weather.”

Male ruby-throated hummingbirds are so small and belligerent that it shortens their lives.

 

(photos taken at the Neighborhood Nestwatch bird banding at Marcy & Dan Cunkelman’s by Kate St. John, 18 July 2015.  Bob Mulvihill is the bander holding the birds.)
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(*) The paper by Robert S. Mulvihill and Robert C. Leberman is entitled A Possible Relationship Between Reversed Sexual Size Dimorphism and Reduced Male Survivorship in the Ruby-throated Hummingbird, published in The Condor 94: 480-489.  It’s available as a PDF here at Sora.  Their work is cited in the ruby-throated hummingbird account at Cornell’s Birds of North America.

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Jul 20 2015

Yellow Shoulders

Published by under Bird Anatomy,Songbirds

Male American goldfinch, two years or older, at banding (photo by Kate St. John)

Male American goldfinch, two years or older, at banding (photo by Kate St. John)

Here’s something we learned at the Neighborhood Nestwatch banding at Marcy Cunkelman’s last Saturday that you won’t notice through binoculars.

Did you know that first-year male American goldfinches look different than the older males?

Full adult males, two years and older, have bright yellow shoulders (scapulars) that match their backs as shown above.  First-year males have a mix of black and yellow on their shoulders.

Here’s a first-year male held by the National Aviary’s Bob Mulvihill while he explains the color.

First-yearmale American goldfinch, at banding (photo by Kate St. John)

First-yearmale American goldfinch, at banding (photo by Kate St. John)

And here’s a side-by-side comparison of the scapulars: full adult on the left, first-year male on the right.  Notice how the younger male has black under the yellow on his shoulder.

Scapulars on 2-year+ male American goldfinch compared to 1st-year male on the right (photo by Kate St. John)

Pure yellow scapulars on 2-year+ male American goldfinch (left) compared to black+yellow on 1st-year male (right) — photo by Kate St. John

First-year males are old enough to breed but they don’t have any experience yet.  Perhaps the ladies use the colors as a signal when picking mates.

If you look closely for the yellow shoulders, you too can separate the men from the boys.

 

(photos by Kate St. John)

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Feb 19 2015

TBT: Cold Feet

Mourning Dove in winter (photo by Marcy Cunklelman)

Throw Back Thursday (TBT)

Unlike many birds, mourning doves are prone to frostbitten toes.  Can they do anything to avoid it?

Last Sunday morning when it was 2o F, two mourning doves flew in to stand on the dry patch in my heated bird bath.  They were warming their feet!

This morning it is zero degrees Fahrenheit so I expect they’ll be back.

Here’s why they need to warm their toes in an article from January 2010:  Cold Feet.

 

(photo by Marcy Cunkelman)

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Feb 08 2015

Both Male And Female

Published by under Bird Anatomy

Bilateral gynandromorph northern cardinal (photo courtesy Western Illinois University)

Bilateral gynandromorph northern cardinal (photo courtesy Western Illinois University)

This northern cardinal has a birth defect that made it both male and female.  The right side of its body is female, the left side is male.

This cannot happen in humans because our sexual characteristics are determined by hormones but in birds each cell has a sexual identity that’s determined early in embryonic development.

On rare occasions something goes wrong during the first cell division and an individual bird is born a bilateral gynandromorph.  In other words, side-to-side (bilaterally) exactly half the body is female (gyn) and the other half male (andro).  The dividing line is always vertical from head to tail.  To understand how this happens, read this 2010 blog post on bird chromosomes: Anatomy: W and Z

In bird species where males and females look the same it’s hard to tell this has happened but in sexually dimorphic species like the northern cardinal or evening grosbeak, it’s easy to see.

This particular cardinal from Rock Island, Illinois is now famous because he-she was studied extensively by Professor Brian Peer and Robert Motz of Western Illinois University.  Their findings — “Observations of a Bilateral Gynandromorph Northern Cardinal (Cardinalis cardinalis)” — were recently published in The Wilson Journal of Ornithology and featured in Science magazine.

Click here to see the press release at Science Daily.

 

(photo courtesy Western Illinois University)

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Nov 29 2014

Red + White Makes …

Published by under Bird Anatomy

White ibis and scarlet ibis (photos from Wikimedia Commons, Creative Commons licenses)

What happens when an American white ibis hybridizes with a scarlet ibis?

The results are pink.

I wish I had a picture of that!  I’ve never seen one.

 

(photos of American white ibis and scarlet ibis from Wikimedia Commons, Creative Commons licenses. Click on the links to see the originals)

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Nov 25 2014

His Name is Cloud

Leucistic red-tailed hawk, named Cloud, at Medina Raptor Center (photo by Kate St. John)

Meet “Cloud,” a leucistic red-tailed hawk at the Medina Raptor Center in Spencer, Ohio.

Cloud is white because there’s no melanin in his feathers, a recessive trait that expresses when both parents pass it on to their offspring.  Cloud is leucistic, not an albino, because he does produce some melanin, shown in his blue eyes (not pink) and yellow legs and cere (not white).

Cloud led a normal life and raised at least one family at a railyard in Ohio until his territorial choice was his undoing.  One day he caught prey on the railroad tracks and did not get out of the way when a train approached.  The train ran over his wing.

His color saved his life.  Because of his beauty he was a favorite with the railyard workers who immediately saw he’d been struck and mobilized volunteers to collect and deliver him to Medina Raptor Center.

Cloud was so badly injured they thought he would die but he fought his way back to health. Unfortunately he will never fly again.  Part of his left wing is missing.

Leucistic red-tailed hawk, back view, at Medina Raptor Center (photo by Kate St. John)

However, he’s now an excellent educational ambassador, teaching people about leucism and the lives of red-tailed hawks.

Thanks to Annette Piechowski at Medina Raptor Center for introducing us to Cloud.  What a beautiful bird!

 

 

p.s. Do you know of any leucistic red-tailed hawks in the wild?  I know of one that used to nest on the Hays hillside in Pittsburgh and another near Millers Pond at Pymatuning.

(photos by Kate St. John)

p.p.s.  You can sponsor Cloud and the other educational birds at the Medina Raptor Center. Click here to see.

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Oct 28 2014

From T-Rex To Hummingbirds

Chart of dinosaur-to-bird evolution (illustration by Steve Brusatte)

Ancient birds have a new family tree.

In a report last month in Current Biology researchers at University of Edinburgh and Swarthmore College analyzed 850 body features of 150 dinosaurs, then used statistical analysis to assemble a detailed family tree from dinosaurs to birds.

Interestingly, they found that the evolution of bird characteristics in dinosaurs was very gradual and non-linear.  Features like feathers, wings and wishbones appeared in many species over tens of millions of years so there is no “missing link” dinosaur line to the first bird.

“This process was so gradual that if you traveled back in time to the Jurassic, you’d find that the earliest birds looked indistinguishable from many other dinosaurs,” said Swarthmore statistician Stephen Wang.

And then, 150 million years ago the bird skeleton came together and bang! there was an explosion in species from the one-of-a-kind hoatzin to more than 350 species of hummingbirds.  According to Science Daily, this explosion “supports a controversial theory proposed in the 1940s that the emergence of new body shapes in groups of species could result in a surge in their evolution.”

Read more here in Science Daily about the family tree.

Most kids go through a dinosaur-loving phase.  Some of us fall in love with birds and never come out of it.  😉

 

(diagram by Stephen L. Brusatte, University of Edinburgh. Click on the image to see the original.)

 

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Oct 16 2014

Woodpecker Toes

Published by under Bird Anatomy

Red-bellied woodpecker's toes, on banding day (photo by Kate St. John)

Here’s a closeup of woodpecker toes from banding day at Marcy Cunkelman’s last July.

Look at the direction of the toenails and you can you tell they belong to a woodpecker.  Two claws curl forward, two curl back.

Woodpeckers have zygodactyl feet that help them cling to tree trunks.

The other foot from the same red-bellied woodpecker shows his toes open — two forward, two back.  Notice that the toes aren’t all the same length.  The little toe is Toe #1, the hallux.

Red-bellied woodpeckertoes, foot open on banding day (photo by Kate St. John)

 

Most perching birds have three toes forward while the hallux points back: anisodactyl feet.  (You might recognize these toes from yesterday’s Swainson’s thrush photo.)

Feet of Swainson's thrush (cropped photo from Wikimedia Commons)

Anisodactyl is the most common form but there are four other arrangements of birds’ toes.  Read more and see a diagram at this blog post from 2010.

 

(woodpecker photos by Kate St. John. Swainson’s thrush feet are cropped from a photo on Wikimedia Commons. Click on the Swainson’s toes to see the original photo)

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Aug 20 2014

Birds Can Recover Lost Hearing

Published by under Bird Anatomy

Dr. Edwin Rubel works to restore human hearing by studying birds (photo from Univ of Washington Dept of Medicine )

Dr. Edwin Rubel studies chicks’ ability to re-grow their hearing nerve cells. Univ. of Washington Dept of Medicine

My visit to an audiologist for a baseline hearing test revealed an awesome thing about birds.

This summer I had my hearing tested because I noticed I could still hear faint rustling sounds with my right ear but not with my left.  For a long time my left ear has been slightly “less good” but this spring was the first time I didn’t have stereo for everything.  I was looking in the wrong direction for the very quiet birds.

The hearing test showed that my right ear is still above average but I’ve begun to age and am very slowly losing the top end of sound.  My left ear has lost more than my right — hence the lack of stereo — but for a human I have good hearing.  The sounds I’ve lost would only be noticed by a cat (or a birder).  Since those sounds aren’t in the “human” range, the loss is not correctable.

But if I was a bird, I could correct it myself.

We hear thanks to tiny “hair cells” that line the cochlea of our inner ear.  Not “hairs” at all, they are actually protein-filled protrusions that vibrate when sound reaches them and transmit it electronically to the brain.  Age, loud noises, and toxins, including strong antibiotics, damage these cells.  Mammals cannot regenerate hair cells.  Birds can!

The photo above, from a 2004 article at the University of Washington’s Department of Medicine, shows the man who discovered this with a bird that helped him prove it.  In the late 1980’s Dr. Edwin Rubel at the University of Washington and Dr. Doug Cotanche at the University of Pennsylvania simultaneously discovered that birds can recover their hearing.  After hair cell loss they grow the hair cells back again!  Later research uncovered this same ability in fish.  (Click here for the 2004 UW article and here for information in the 2012 Hearing Journal.)

Their discoveries have led to work on a wide range of possible solutions, none of which are perfected yet.

For now, I compensate when I hear a faint bird sound — I turn my head.

Some day, thanks to birds, there may be a cure for us mammals.

 

(photo of Dr. Edwin Rubel from a 2004 article about his research at the University of Washington Department of Medicine)

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Aug 06 2014

The Better To Eat With, My Dear

Published by under Bird Anatomy

Immature red-bellied woodpecker shows his bony tongue (photo by Kate St.John)

During the Neighborhood Nestwatch banding at Marcy Cunkelman’s last month I learned an amazing thing about the red-bellied woodpecker.  The tip of his tongue looks like a spear.

We saw this firsthand when an immature red-bellied shouted and displayed his tongue while he waited to be banded.

Here’s a closer look.  You can see that his tongue is pointed and bony and coated with inward-facing barbs.

Red-bellied woodpecker has a bony tongue (photo by Kate St. John)

Not only is the tip of his tongue very specialized, but the entire tongue is extra long and easy to maneuver.  Under his skin, his tongue begins in front of his eyes and wraps over his skull to emerge in his mouth. This gives it enough slack that he can stick it out 1 to 1.5 inches beyond his bill.

This long maneuverable spear allows him to capture bugs and larvae in deep crevices.  He hammers the crevice, sticks out his tongue, maneuvers it inside the crack and stabs his prey.  If he doesn’t completely spear it, no problem.  He has specialized mucus that makes his tongue sticky.

Click here to see an illustration and photo of the red-bellied’s amazing tongue.

The better to eat with, my dear.

 

(photos by Kate St. John)

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