White-throated sparrow (photo from Wikimedia Commons, Creative Commons license)
Even before the buds burst and the flowers bloom, birds give us a hint that spring is coming. Some of them turn yellow.
* White-throated sparrows have boring faces in the winter but their lores turn bright yellow ahead of the breeding season. They’ll leave in March or early April for their breeding grounds in the northern U.S. and Canada.
* American goldfinches were brownish all winter but molt into yellow feathers in late winter. Even the females turn a subdued yellow as seen in the female on the left in Marcy’s photo.
Goldfinches turning yellow for spring (photo by Marcy Cunkelman)
* At this time of year European starlings become glossy and their beaks turn yellow. The starling below is male because the base of his beak is blue (near his face).
European Starling in breeding plumage (photo by Chuck Tague)
There are other birds whose yellow facial skin becomes brighter in the spring. Can you think of who that might be? …
Yellow is a sign of spring.
(photos from Wikimedia Commons, Marcy Cunkelman and Chuck Tague. See credits in the captions)
Have you ever seen a distant white raptor and hoped it was a snowy owl? I have, but I’m usually wrong. Snowy owls only visit Pennsylvania in late fall or winter and even when they’re in Erie County they rarely come to southwestern Pennsylvania.
What about a white gyrfalcon? Gyrfalcons are extremely rare in Pennsylvania and in North America they are usually brown, not white. In over 100 years only 41 gyrfalcons were reported statewide, always in the winter (see *1 below). The last gyr to visit southwestern PA was in 1913.
And yet we occasionally see a rare white raptor, even in summer. What hawk is this? In nearly every case it’s a leucistic red-tailed hawk (Buteo jamaicensis).
“Leucism is a condition in which there is partial loss of pigmentation in an animal resulting in white, pale, or patchy coloration of the skin, hair, feathers, scales or cuticle, but not the eyes.” (quoted from Wikipedia). The condition is rare but red-tails are our most common hawk so it’s not surprising to find it in a numerous population.
The whiteness varies from hawk to hawk and even as they molt from year to year. Sometimes leucistic red-tails are spotted brown, sometimes they’re entirely white. Pat Gaines photographed a speckled one in Berthoud, Colorado in 2017 and an all-white bird in North Denver in 2010. Neither bird is albino because its eyes are the normal dark color, not pink.
It’s a very rare condition and it only happens when there’s an embryo error in the bird’s sex chromosomes, W and Z. The resulting oddity is a “bilateral gynandromorph.”
Learn how it occurs in this last-day-of-the-year article … Anatomy: W and Z
(photo credits: evening grosbeaks at the Smithsonian by ap2il via Flickr, Creative Commons license. Northern cardinal courtesy of Western Illinois University. Click on the captions to see the originals.)
Diagram of a turkey’s head and chest ornaments (image from Wikimedia Commons)
The two wild turkeys at top are displaying to females. Which one has the best snood? I can’t tell but the females can. Click here to see how the ladies reacted.
(photo credits: two wild turkeys by Cris Hamilton; women wearing snoods from Wikimedia Commons; man wearing a beard snood from sales page at Creeds UK; wild turkey diagram from Wikimedia Commons. click on the images to see the originals)
Thirty years ago Japanese trains had a problem. They could travel fast but they caused sonic booms.
The answer was the bullet train. How did Japanese engineers develop it? They learned from birds.
Watch this 6+ minute video from Vox + 99% Invisible to learn how birds showed the way and follow one woman’s quest to teach engineers that Nature has the answers. Our world can benefit from biomimicry.
For best results, copy birds.
Thank you to Holly Hickling for sharing this. For more cool videos, follow Vox (news site) or 99% Invisible (city design updates) on Facebook.
Yellow-rumped warbler in autumn (photo by Cris Hamilton)
After most warblers have left for the winter, the yellow-rumped warblers come back to town.
Breeding across Canada and the northern U.S., yellow-rumped warblers (Setophaga coronata) spend the winter in North America as close to us as Ohio and eastern Pennsylvania, though not usually in our area. In late fall they stop by in Pittsburgh.
Yellow-rumps don’t have to leave for Central or South America because they have a unique talent. Their bodies can digest wax. In winter they eat the waxy fruits of bayberry and juniper. Since bayberry is also called wax myrtle, it gave our common subspecies its name: the myrtle warbler.
On Throw Back Thursday, learn how yellow-rumped warblers get nutrition from wax in this vintage article: Anatomy: Wax Eaters.
p.s. Notice that the warbler in the Wax Eaters article is wearing bright breeding plumage in black, white and yellow . Autumn yellow-rumps are dull brown with a faint vest and a broken white eye ring. The best clue to their identity is their yellow rump.
Yellow-rumped warbler showing its yellow rump (photo by Cris Hamilton)
Model of Archaeopteryx on display at Geneva natural history museum (image via Wikimedia Commons**)
Birds have no teeth but that wasn’t always the case. We know that they’re descended from toothy theropod dinosaurs — in fact birds are dinosaurs — so when did they lose their teeth?
In 2014, genome sequencing studies led by Robert W. Meredith worked to determine whether several branches of birds’ ancestry lost their teeth independently (convergent evolution) or whether all birds have a common ancestor that evolved a toothless beak.
The project did full genome sequencing on 48 birds species representing nearly all modern bird orders. They then focused their study on six genes related to tooth enamel. All six genes became non-functional in a common bird ancestor around 116 million years ago. That’s when birds lost their teeth.
Birds eat plenty of things that require chewing so how do they do it? Read this 2010 blog post Anatomy: Where Are Their Teeth? to find out.
(cropped image of Archaeopteryx model on display at Geneva natural history museum via Wikimedia Commons; click on the image to see the original. **Note that this Archaeopteryx model has accurate teeth but has other inaccurate/disputed features as described on Wikimedia Commons: “Archaeopteryx had a more round shape of its wings, the primary feathers were attached to the second finger unlike here, and these colours are now known to be wrong.”)
Adult peregrine falcon in flight, Univ.of Pittsburgh, 2016 (photo by Peter Bell)
Now’s a good time to brush up on identifying peregrine falcons since they pass by hawk watches in October, especially on the coast. When you identify a peregrine you can also tell how old it is because the plumage is different in each age group: adult, juvenile, and sub-adult.
Plumage provides an exact age for two groups in October: Juveniles are first year birds, 6 months old, that hatched last spring. Sub-adults are second year birds, 18 months old, with nearly complete adult plumage.
Adults — two or more years old — all have the same plumage. Unfortunately you can’t know an adult’s exact age unless the bird is banded and you find out its provenance.
Here’s what they look like:
Adult peregrines (2+ years old in October) have fresh plumage in charcoal gray and white. The photo at top shows an adult male in flight. The photo below is an adult female. Adults have:
Solid dark charcoal helmet (head)
Dark charcoal malar stripes (on face)
Clean white or slightly rosy chest and throat
Horizontal charcoal+white stripes on belly and flanks
Gray back: Male’s is pale blue-gray. Female’s is “muddy” gray.
Adult peregrine, Univ of Pittsburgh, 2017 (photo by Peter Bell)
Juvenile peregrines (6 months old in October) are the same size as adults but their colors are brown+cream. Juveniles have:
Variable brown helmet with some cream-colored traces (head)
Brown malar stripes (on face)
Cream colored chest that’s striped all the way up to the throat
Vertical brown+cream stripes on belly and flanks
Brown back.
(Bonus!) Juveniles have cream-colored tips on their tails, visible as the sun shines through them in flight.
Juvenile peregrine in flight, Univ of Pittsburgh, 2012 (photo by Peter Bell)
Above, a juvenile in flight. Below a juvenile shows off the vertical stripes on his chest and belly. His variable brown helmet with “eyes on the back of his head” and horizontal cream-colored line at his crown.
Juvenile peregrine falcon, Univ. of Pittsburgh, 2016 (photo by Peter Bell)
Sub-adults are 18 months old with nearly complete adult plumage except for a few juvenile feathers. They began to molt into adult plumage last spring at 10-12 months old. By October their few juvenile feathers are hard to see without a photograph. They are ready to breed next spring.
Below, an 18-month-old peregrine named Spirit is in rehab at Medina Raptor Center in the autumn of 2014. You can see her back is mostly gray with just a few brown feathers. Her head shows faint traces of the juvenile cream colors.
18-month-old peregrine falcon, Spirit, in rehab at Medina Raptor Center, Nov. 2015 (photo by Kate St.John)
(all photos taken at University of Pittsburgh by Peter Bell … except for the peregrine on the glove, “Spirit” at Medina Raptor Center, photo by Kate St. John)
Northern cardinals in May (left) and February (right) . photos by Cris Hamilton.
25 August 2017
Why do birds look fat in winter and thin in the summer? Have they lost weight?
No. They’re thin because they’re trying to stay cool.
Underneath their smooth outer feathers, birds wear down coats all year long. The down is warmer when it is fluffed out to hold heated air near the skin. Our puffy down coats use the same principle. Both we and the birds look fat on cold winter days.
When it’s hot, birds cannot take off their down coats so they force hot air out of the down feathers by compressing their outer feathers and squeezing down the fluff. This makes them look thin. It is counter intuitive to us because tight clothing makes us feel hot so we wear loose clothing in the heat.
The cardinal on the left, above, is not the thinnest one I’ve ever seen. Cris Hamilton took his picture in May when the temperature was pleasant. He’d look considerably thinner this month.
It’s just another way that birds cope with heat.
p.s. We think of down as white but northern cardinals have black down and black skin as seen in this photo of a bald cardinal by Matt Webb. Notice that the downy base of the feathers is black.
Bald northern cardinal, June 2015 (photo by Matt Webb)
