Birds that eat insects leave Pennsylvania for the winter but the omnivores, like this house sparrow, stay behind. Food won’t be a problem but it’s going to get cold so the house sparrows get ready in advance.
A study by Lowther and Cink in 1992 found that house sparrows (Passer domesticus) prepare for winter by molting into heavier plumage. Plumage weight increased 70% between August and September alone. Summer weight is 0.9 grams; winter weight is 1.5 grams.
In September the house sparrows put on their winter coats.
(photo from Wikimedia Commons; click on the caption to see the original. This article was inspired by page 153 of Ornithology by Frank B. Gill, 3rd edition.) )
Because the barn swallow is very widespread and nests almost exclusively on man-made structures, it’s been easy to study this bird for a very long time. One interesting finding is that Hirundo rustica’s long tail streamers (outer edge tail feathers) are an excellent indicator of the birds’ health and a predictor of breeding success.
Birds with the longest and most symmetrical tail streamers are the healthiest and most desirable mates. According to Cornell’s Birds of North America, “Tail length tends to correlate with reproductive success, annual survival, propensity to engage in extra-pair copulation, parental effort, ability to withstand parasites, immunocompetence, and other measures of fitness.”
In other words, if you’re a barn swallow with a long symmetrical tail you’re really healthy, you get to choose the best mate, and your nest will be very successful. You’re also likely to be an older bird because tail length increases with age.
The down side is that long-tailed females are fickle. They always get the best mates but even when they’re paired up they often “mess around” with un-mated long-tailed guys. “Thus long-tailed male barn swallows are cuckolded more often than their less attractive neighbors,” says Frank B. Gill.
The longer the tail streamers, the better the bird. I’ll be watching their tails now.
We all know that wearing black is hot in the sun but did you know that it’s cooler than other colors when there’s a breeze?
According to page 154 of Ornithology by Frank B. Gill: “The cooling effects of wind are most pronounced on black feathers, which concentrate solar heat near the surface of the plumage. Black feathers can increase the amount of heat that a bird’s body absorbs from the environment when there is no breeze. A light breeze, however, removes the accumulating surface heat and reduces further penetration of the radiant heat.”
“The black plumage of desert ravens increases convective heat loss, as do the robes and tents of Bedouin tribes in the Sahara.”
Whoa! Black tents! I had no idea people used black tents in the desert. (Obviously I’ve not been paying attention.)
Here’s a photo of a Bedouin tent in Jordan. Notice that the top is black! The cloth is woven from the hair of their black goats.
The raven knew that black was cool long before people found out. His outspread wings look like a black tent.
(photo of a raven landing near a tent in Death Valley National Park via Wikimedia Commons. Photo of a Bedouin tent by Anita Gould, Creative Commons license via Flickr. Click on the images to see the originals. Today’s Tenth Page is inspired by page 154 of Ornithology by Frank B. Gill.)
excerpt link to Afghanistan: An Atlas of Indigenous Domestic Architecture by Albert Szabo, Thomas Jefferson Barfield.
In this week’s very cold weather it’s hard to stay warm but birds have a few strategies that help.
They eat a lot and they also naturally shiver to stay warm. Shivering sounds pathetic but it actually works because the muscles generate heat. The big pectoral (breast) muscles are the best for this.
Some birds shelter in nooks or crannies of hollow trees or on the outsides of our buildings. Look at chimney tops and you’ll see starlings absorbing the warm exhaust. On Monday I saw a peregrine at Pitt facing inward at a high window on the Cathedral of Learning. The window was warmer than the surrounding air.
Other birds come indoors. On Monday afternoon Richard Nugent reported he’d found a Carolina wren sheltering in his heated garage as the temperature was heading for -12 degrees that night. What a smart wren! Richard put out food and water for the bird to enjoy while it waited for the weather to improve.
Huddling helps. Inca doves not only huddle sideways as shown above but they make pyramids two or three rows high. According to Ornithology, as many as 12 Inca doves will form a pyramid, fluff their feathers and face downwind in a sheltered sunny place. “In large pyramids, doves exposed on outside positions try for better positions in the top row and cause the whole pyramid to readjust.” This sounds like a circus act, amazing to watch.
Last night was the last of the bitter cold. If the birds can make it through today the weather will moderate, then switch to above-normal temperatures this weekend.
On this very cold morning everyone’s working hard to stay warm but some have an easier time than others. Who loses heat faster, the chickadee or the raven?
Just like us, birds burn calories no matter what they’re doing. However, birds have higher metabolic rates than mammals and require more calories for everything they do. Any activity, from sleeping on an empty stomach to a burst of rapid flight, burns more energy than in vertebrates of a similar size.
Small birds have higher metabolic rates than large ones because of the relationship of surface to volume. Heat dissipates from the surface of an object so the more surface there is, the greater the heat loss. So, yes, the chickadee loses heat faster than the raven. That’s why northern animals are often larger-bodied than those who live in warmer climates. Even among chickadees the black-caps in Maine are noticeably larger than the chickadees in Pittsburgh.
To stay warm the chickadees will look fatter today because they’ll fluff their feathers to raise the loft of their down coats. They’ll also cover their legs to reduce heat loss and they will eat — a lot! — to replace the calories they’re rapidly burning.
“Eat like a bird?” Today all birds, and especially the little ones, are chowing down to stay alive.
This week I read about colonial nesting in Ornithology by Frank B. Gill. “About 13% of bird species, including most seabirds, nest in colonies. Colonial nesting evolves in response to a combination of two environmental conditions: (1) a shortage of nesting sites that are safe from predators and (2) abundant or unpredictable food that is distant from safe nest sites.”
The book mentions king penguin colonies; sometimes they’re huge. This one is on the Salisbury Plain of South Georgia, an island in a volcanic ridge that arcs from the southern tip of South America to the northern tip of Antarctica. (Click here to see where it is on Google Maps.)
There are lots of king penguins in the photo above, but zoom out below and the number is stunning. Half a million king penguins in one place!
Obviously the advantages of living like this outweigh the disadvantages of occasional social strife, epidemics, or the crash of the food supply.
Imagine being in a place where there are penguins as far as the eye can see!
(photos from Wikimedia Commons. Click on the images to see the originals. Today’s Tenth Page is inspired by page 330 of Ornithology by Frank B. Gill.)
The practice of giving plum jobs to your relatives is widely frowned upon but nepotism is a very successful survival strategy — so successful that some birds use it too.
Closely related to North America’s gray jay, Siberian jays (Perisoreus infaustus) live in the boreal forest of Northern Europe. Like other corvids in limited habitats they breed cooperatively. Each breeding pair has a suite of relatives who help guard the nest and feed the young. Often the kids stay with their parents even though they’re old enough to breed.
Studies in Sweden have shown that male Siberian jays who stay with their parents are much more successful than those who leave home because their fathers practice nepotism. The father jays protect their own sons and harass incoming males who try to join the group. The sons thrive and learn while they wait for a good territory to become available.
The exception proved the rule. Ekman and Griesser experimentally removed fathers and watched as they were replaced by despotic immigrant males who ejected the missing fathers’ sons. If dad’s not there to protect you, watch out!
Success through nepotism.
(photo from Wikimedia Commons. Click on the image to see the original. Today’s Tenth Page is inspired by page 390 of Ornithology by Frank B. Gill.)
Chances are these turkeys are brothers, working together to chase the police out of their territory.
Wild turkeys are very social birds whose flocks are often composed of siblings. This habit starts young when they’re all poults together and continues as adults.
Each sex within the flock develops a pecking order. Literally. Who has the right to peck someone else? The ladies figure out the hierarchy and tend to leave it at that without a lot of jostling. The guys, on the other hand, are always stirring things up. Which of them is most dominant? They fight about it. In this case they’re fighting a police car.
Turkeys are brothers in love and war. Groups of male turkeys strutting and displaying together are usually brothers, collaborating to attract the opposite sex. One of them is dominant and he’ll get to mate with the ladies. His brothers display but they don’t become fathers.
But don’t feel sorry for the lesser guys. Soon enough they’ll fight about it and a different male may achieve dominance in the band of brothers.
(photo from Wikimedia Commons of two male wild turkeys chasing a police car in Moorhead, Minnesota on April 29, 2013. Click on the image to see the original. Today’s Tenth Page is inspired by page 338 of Ornithology by Frank B. Gill.)
Though juvenile mortality is high, birds are amazingly long-lived if they survive to adulthood. What’s the key to their longevity?
In 2011 scientists at the National Evolutionary Synthesis Center in Durham, NC crunched 27 years of data on more than 1,200 birds to examine mate selection, fertility and aging. They used the rich data set on blue tits, a bird similar to our chickadees, studied on the island of Corsica since the late 1970’s. Aging was easiest to see among female blue tits because their fertility dropped if they lived long enough. They laid fewer eggs and laid them later in the season than females in their prime.
Interestingly the study found that females remained in their prime longer if they had good mates. Their fertility did not wane so soon, they aged more slowly. This was especially true for the ladies whose mates became fathers at an early age.
The good males were better helpers during the nesting season. They shared parenting duties and were solicitous for the females’ well-being. They brought food to their ladies and eased the burden of nest building, incubation and child rearing. The team’s scientists conjectured that the males who became fathers at an early age were not only more experienced at this but were also healthier.
The good mate scenario sounds a lot like Dorothy and E2’s relationship. Every nesting season we see E2 on camera bringing food to Dorothy and the kids, begging to take over incubation duties, and sometimes refusing to give them up. Even in the off season, those of us who watch this peregrine pair see E2 bring food to Dorothy throughout the year. What a guy!
p.s. A study published this year showed this principle is true for humans, too. Happily married couples live longer, healthier lives than their single counterparts. Thank you to my husband on our anniversary.
In one way this is very old news. In another way it’s sadly up-to-date.
In the early days of radar surveillance, scientists learned that those mysterious blobs on the screen in spring and fall were flocks of night-migrating birds. In 1965, as part of his graduate study at Louisiana State University, Dr. Sidney A. Gauthreaux, Jr. studied spring migration using radar images at Lake Charles and New Orleans along with his own on-the-ground counts as birds flew past his light beam or the moon.
Twenty years later, the news said that songbirds had declined. Gauthreaux wondered if this was evident on radar so he collected data from the same two sites and compared the images from good-weather migration nights in 1965-1967 to those in 1987-1989. In only 20 years he could see that the number of migrating songbirds had declined by 50%. Half the number of warblers, tanagers, hummingbirds, shorebirds, flycatchers and thrushes made the trip.
That was 24 years ago. It has only gotten worse. I don’t know of a recent radar comparison (was there one comparing the 1980’s to 2000’s?) but our ground-based counts show that birds such as the king rail, cerulean warbler and olive-sided flycatcher are in dangerous decline now. Just last month the eastern red knot was proposed for Endangered Species protection by US Fish and Wildlife.
Meanwhile, it seems ironic that so many people are becoming interested in birds while birds are becoming scarce, but it’s a good thing too. The more of us that care about birds, the more likely we’ll learn what they need and work to insure their future.
(screenshot of NOAA weather radar, 9 Oct 2013, 6:38am EDT. Click on the image to see the current radar page. Today’s Tenth Page is inspired by page 278 of Ornithology by Frank B. Gill.)
p.s. This NOAA image shows the radar stations that were part of Dr. Gauthreaux’s study. On Wednesday morning the weather concentrated migrants east of the Mississippi as they approached the Gulf Coast.