If you live in North America this fact is amazing: House sparrows are an endangered species in Britain.
I learned this when I read John Metcalfe’s article called Making Cities More Bird Friendly With Nesting Bricks. In it he describes a new brick specially designed by Aaron Dunkerton and manufactured in England to provide habitat for nesting house sparrows. Before mortar is applied it looks like this. (Click on the bricks to read about them.)
House sparrows are the most widely distributed wild bird on earth. Why are they so endangered in the U.K. that people invent ways to help them? Here’s what I found out.
The greatest house sparrow declines occurred where nestlings starved within a week of hatching or had low fledging weight, both due to lack of insect prey. The best success occurred where they ate plenty of aphids or spiders. (Aphids come up again!)
Because house sparrows nest in holes in buildings, they did well in neighborhoods built before 1919, in neighborhoods where soffitt and fascia were made of wood, and in distressed neighborhoods where the buildings needed repairs. They avoided neighborhoods built after 1985 because of new construction standards and lack of deterioration. That’s why Aaron Dunkerton invented the bird brick for new homes.
House sparrows did poorly in tidy neighborhoods with lots of paving. Over the years Britons have paved their front yards and removed trees and shrubs so they can park their cars. This has reduced house sparrow habitat.
All habitat was not equal. House sparrows preferred deciduous plants and the insects associated with them.
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)