African starlings evolve color faster than any other bird — 10 times faster than their ancestors and modern relatives according to a new study from the University of Akron.
Like other Sturnidae these birds had iridescent qualities, but after they made it to sub-Saharan Africa 17 million years ago their colors went wild. The cells that give their feathers iridescence are called melanosomes. Instead of the usual simple rod-like forms, glossy starlings (Lamprotornis) developed hollow rods, solid flattened rods, and hollow flattened rods. Though these divergent melanosomes are sometimes found in other birds, glossy starlings can have all the variations in one species. This produced an explosion of new colors.
At the University of Akron Rafael Maia studied microscopic feather structures and used spectral color analysis and evolutionary modelling to figure out how these starlings evolved four types of melanosomes and 19+ species. It happened very fast.
Their social structure helped. For glossy starlings, color confers high rank in both sexes so the most colorful birds are the most successful breeders. Intense social pressure selected for better and better colors.
The lyrics of the Beatles’ Blackbird song used to puzzle to me. What blackbird sings in the dead of night? In eastern North America I didn’t know of any blackbirds that did that.
My worldview was too small. North American blackbirds are icterids: Brewer’s, red-winged, rusty, tri-colored and yellow-headed. In England common blackbirds are thrushes, a single species Turdus merula similar to the American robin.
The common blackbird’s song is complex, varied and beautiful. His syrinx allows him to sing two songs simultaneously and even harmonize with himself. In the video above he starts out loudly on a perch, then drops to the ground and whisper-sings just like a robin. Like our robins he also sings at night.
And watching a sora cross the road. He made himself into a ball so he looked like a very slow, round muskrat without a tail (was this camouflage?) and risked his life by walking slowly in front of traffic. Fortunately all the drivers were birders and we stopped to stare and spare his life.
When Charlie posted these photos on his Flickr account he alluded to Edgar Allen Poe’s Raven and wrote, “In spite of Carole opening the door and the trash pickup, [the robin] kept returning until Carole covered the kickplate with the door mat.”
Spring is moving north and so are the robins. This week a big wave arrived after Monday’s snow. Now that they’re here, how soon will they nest?
Robins nest later the further north you go. In 1974 Frances James and Hank Shugart were curious about the conditions that governed their nesting times throughout the U.S. Using climate data and Cornell nest watch information from 8,544 robins’ nests they developed a model that predicted when robins would nest in a particular region.(*)
The model shows that robins cue on weather. Hatching is timed to occur when local humidity is 50% and temperatures are between 45 and 65 degrees Fahrenheit. By April 23, Pittsburgh’s highs and lows are exactly in that range so our birds are getting ready. Here’s what they’re up to:
Robins spend 5-7 days building their first nest of the season.
Egg laying begins 3-4 days after first nest completion.
Eggs are laid one per day for a clutch of 3-4 eggs.
Incubation lasts 12-14 days.
From nest building to hatching, the first nest takes 26 days. (Subsequent nests take less time.)
Our robins should be nest building right now except for one thing: Do they have enough mud to begin construction? Has the mud been frozen?
Watch the robins in your neighborhood to see what stage they’re in. Join Cornell Lab’s Nest Watch program and your data can become the basis for studies like James’ and Shugart’s that broaden our knowledge of birds.
(Credits: photo by William Majoros on Wikimedia Commons. Click on the image to see the original.
Today’s Tenth Page is inspired by page 260 of Ornithology by Frank B. Gill, portions of which are quoted(*) in this article.)
We’re starved for thrashers in Pittsburgh right now. Of the eight species in North America only one, the brown thrasher, occurs in the eastern U.S. and he’s away on migration. All the rest are western or southwestern birds, several of which occur in California.
This one has “California” in his name. He doesn’t migrate — in fact he hardly moves away from his birthplace — so if you want to see him you have to be in California or northern Mexico.
The California thrasher loves dense desert chapparel but is sometimes found in scrubby or suburban habitat where he encounters a bird whose habits are quite similar.
Northern mockingbirds eat the same food and forage in the same way as California thrashers. Both are highly territorial so when a mockingbird moves into a thrasher’s territory constant warfare ensues.
Imagine the two contestants hopping and lunging.
Hey, Mr. Mockingbird, watch out for that beak!
Fortunately for northern mockingbirds, few of them like dense chaparral so these species are usually in separate places.
Good for the thrasher too. What a waste of energy to be constantly thrashing it out!
(photo by Alan Vernon from Wikimedia Commons. Click on the image to see its original)
Have you noticed? There aren’t many robins in Pittsburgh right now.
In December it was another story. Every day I watched hundreds feast on the ornamental fruit trees in Oakland. Their numbers fell slightly in early January, then surged again on the 13th when I saw so many that I recorded their number as ∞ (infinity) in my notebook.
But they ate all the fruit and the ground was too frozen to find worms and invertebrates, so they left. If I’m lucky I see one or two robins a day.
This situation is only temporary. The robins wintering in Florida are getting restless. Soon they’ll come north, following the 37oF average daily temperature isotherm and the arrival of the Spring.
Much as we’re unhappy with the results, the introduction of house sparrows from Europe began a grand experiment in avian adaptation.
House sparrows were introduced to both the U.S. and New Zealand in the 1850s where they immediately became isolated from their native populations. More than 150 years later they differ based on where they live.
In addition to changes in plumage the birds are different sizes. In locations where winters are harsh, the birds are large. Where the climate is moderate, they are smaller. This effect is called Bergmann’s rule and is true of birds around the world.