Speaking of owls, as I did on Thursday, here’s a portrait of one of the world’s largest owls, the Eurasian eagle-owl.
Bigger than a snowy owl he is slightly outweighed by the endangered Blakiston’s fish-owl of Asia and has a slightly shorter wing span than the great gray owl.
Despite these technicalities he is virtually the world’s largest owl. With females weighing up to 9.3 pounds they are bigger than our great horned owl (up to 5.7 pounds), the eastern screech-owl (weighing up to 1/2 pound), and the northern saw-whet owl (weighing only as much as 1/3 pound). The two smaller owls are dinner for the great horned owl. Imagine what a Eurasian eagle-owl eats!
To get an idea of owl sizes, visit the National Aviary to see the eagle-owl and others up close.
(photo from Wikimedia Commons. Click on the image to see the original)
If you haven’t been watching PixController’s eastern screech-owl webcams you’ll want to start now.
Back in October when I first wrote about the webcams, eastern screech-owls were just starting their winter-roost season. The birds hadn’t chosen preferred boxes and a squirrel was time-sharing in one of them.
Since then two owls have sorted out who roosts where. They’re definitely aware of each other because they sometimes visit each others’ roosts or eat each others’ cached food.
This week they’ve been busy in Owl Boxes #2, #6 and #7. On Tuesday night the owl nicknamed “Allie” caught and cached a mourning dove in Owl Box #2. Last night she came back to eat it. The motion detection cameras keep track of the owls so you don’t have to stay up all night. Click here to see recent archives of owl activity.
Now that Winter is ending, things are about to get very interesting. Eastern screech-owls nest in March. Will they nest in one of the boxes?
Click here or on the image above to watch PixController’s Eastern Screech-owl Live Webcams. You can also follow PixController on Facebook where Bill Powers posts the day’s best photos from his many webcam installations.
If you have to sit outdoors in winter, you’re bound to get snowed on.
Last month during a particularly wet snowfall, Gregg Diskin found this red-tailed hawk perched in Schenley Park. The bird was trying to stay warm and dry but it was a challenge. His feathers were wet and his feet were getting cold.
See how he’s tucked one foot into his breast feathers? It looks like he’s holding his coat closed. Brrrrr!
Fortunately feathers are very good insulation. You don’t realize how well they work until the hawk scratches his head.
We’re not the only ones who celebrate love this month. February is raptor courtship time.
Last year on Valentine’s Day the Decorah Eagles nestcam captured the bald eagles, “Mom and Dad”, vocalizing and mating.
This year the eagles have built a second nest that’s closer to the fish hatchery and not on camera! At this point it’s unclear which nest the eagles will use, but they’ll certainly disappoint their 60,500 followers if they choose the off camera site.
Pittsburgh’s “falconuts” experienced that disappointment a year ago when Dori and Louie chose a new nest site Downtown. Unfortunately it looks like the peregrines aren’t coming home to the Gulf Tower so we’re going to have another year of off-camera love birds.
Max, a dog who finds owls + an owl in the background at top left (photo by Jennifer Hartman, Univ of Washington)
6 February 2013
How do you survey a population of owls that are afraid to make noise? Dogs to the rescue!
In 1990 northern spotted owls were listed as Threatened under the Endangered Species Act. Since then their population has been surveyed year after year, but despite changes in logging practices northern spotted owls continue to decline 3.7% per year.
Part of the problem could be that some owls have fallen silent and are impossible to count. The typical survey method is to play an owl recording and listen for the owl to respond. But barred owls have infiltrated the old growth forest, displaced northern spotted owls, and sometimes killed them. Some northern spotted owls would rather not respond when the tapes are played. They don’t want to give themselves away.
So how do you count these owls?
Researchers at the University of Washington trained two dogs, Max and Shrek, to identify owl pellets by species! Amazingly, the dogs can smell the difference in regurgitated mouse bones from a barred owl versus a northern spotted owl.
The team takes the dogs out for a spin in the forest. They don’t use recordings at all. The dogs sniff for pellets below owl roosts and are so good at identifying the species that they have a 30% better success rate at finding northern spotted owls than the recordings do.
Here’s Max triumphant. See the northern spotted owl in the tree above him?
How do owls turn their heads this far without killing themselves?
Trauma experts know that when humans turn their heads too far or too fast the arteries to the head are stretched or torn, cutting off the blood supply or producing blood clots that can kill.
Why doesn’t this happen to owls? A team at Johns Hopkins decided to find out.
Led by medical illustrator Fabian de Kok-Mercado, they used imaging technology on barred, snowy and great horned owls who had died of natural causes. The researchers found four adaptations that make the owls’ wide range of movement possible:
As in humans, the major arteries that feed the brain go through bony holes in the vertebrae but in owls these holes are 10 times larger than the arteries, allowing them to move within the hole without pinching.
The owls’ vertebral artery enters the neck higher up than in other birds — in the 12th vertebrae rather than the 14th. This provides more slack.
When an owl turns its head the arteries at the base of the head balloon to take in more blood. In humans the arteries get smaller and smaller.
Owls also have small vessel connections between the carotid and vertebral arteries so if one path is blocked the other still works.
A simple turn of the head that’s so hazardous to us is all in a day’s work for an owl.
Peregrine fans, does this photo remind you of someone?
This scene is from Baringo Cliffs, Kenya where a lanner falcon attacked a Verreaux’s eagle and forced it to flip upside down to defend itself.
Lanners are about the size of peregrines and they hate eagles just as much as our peregrines do.
The photographer, Steve Garvie, describes it this way:
“A pair of Lanner Falcons were nesting at one end of the cliffs and this massive female Verreaux’s Eagle drifted into their airspace. The female Lanner took to the air and quickly gained height then she flapped twice twisted onto her side then plunged in a deep stoop striking the circling eagle on the back of the head. The female eagle got a sore one and as the Lanner approached again she flipped upside down and clearly indicated there would be no second chance!”
Half a world away on June 6, 2012, Pitt’s famous peregrine Dorothy saw a bald eagle approach her “cliff” at the Cathedral of Learning. She too flapped a couple of times and then attacked. The bald eagle flipped upside down but it didn’t matter. Dorothy won.
Eagles, whether Verreaux’s or Bald, can’t fly upside down for long. Though Garvie doesn’t say it, I’m sure the lanner drove the eagle away just as Dorothy did at Pitt.
Great gray owls (Strix nebulosa) live in coniferous forests and taiga of the North. Their year-round range extends into upper Minnesota where this one was filmed in March.
In the video you’ll see two clips of the owl avoiding detection by two other species: a bald eagle and a raven.
Don Weiss photographed this dark-morph rough-legged hawk at Miller’s pond in Crawford County last weekend. In winter it’s a reliable place to find this typically northern bird.
As winter approaches our local wildlife looks for safe, dry places to take shelter from the cold. Eastern screech-owls use hollow trees, dense foliage and holes in upright structures.
Last year Bill Powers of PixController set up an eastern screech-owl roosting study with five owl boxes in a dry wetland in Westmoreland County. Each box is equipped with a small infrared video camera and small microphone wired back to a server that detects motion and streams video.
When it turned cold last weekend, Bill’s cameras detected motion as an owl checked out two of the boxes at dawn on Saturday.
Here’s the owl staring up at the infrared camera in Box #1 where he eventually roosted. There’s no color because the light is infrared.
Knowing which box to watch, Bill put up a blind on Saturday and took the owl’s picture when he emerged at dusk. He’s the handsome screech-owl in full color above.
Last night I tuned in at 9:00pm. There were no owls but I found a squirrel in Box #4, rearranging his tail and wrapping it around his body to cover his nose.
Won’t he be surprised if an owl shows up this morning!
Visit Bill’s PixController Screech Owl website to watch the cameras. Click here for more information on the camera setup and a map of the cam locations.
