Any parent can tell you that raising kids is hard work and even harder if there are multiple infants the same age. (Think triplets!)
Most birds experience this multiple effect every time they nest. In fact, the work is so exhausting that having “extra” kids beyond their normal clutch size decreases the parents’ life expectancy in some species.
This was shown in studies of common kestrels in Europe in the 1980s.
A team led by Cor Dijkstra artificially lowered and raised brood sizes of common kestrels by removing eggs from some nests and adding them to others. Kestrel parents whose brood size of five remained normal or was reduced to three experienced the typical winter mortality of 29%. On the flip side, adults whose broods were augmented were much more likely to die the next winter. 60% of the kestrels who raised two extra chicks were dead by the following March.
For thousands and thousands of years the clutch size of the common kestrel has been honed by the deaths of those who raised too many. The birds settled on the number five. More than that can kill them!
(photo of common kestrel nest in Germany from Wikimedia Commons. Click on the image to see the original.
Today’s Tenth Page is inspired by page 521 of Ornithology by Frank B. Gill.)
So many of us have been watching the bald eagles’ nest in Pittsburgh’s Hays neighborhood that we’ve begun to think of them as “our” eagles.
Last Saturday, June 29, was a big day for the young eaglet. After weeks of flapping she lifted off. Tom Moeller photographed her flying for the very first time.
Above she takes off from the area of the nest. Below she crosses over to fly toward her father’s perch. She is huge!
The entire photo series of her first flight is here on Tom Moeller’s Picasa site.
Do you want to watch Pittsburgh’s eagles on the Fourth of July? Join the Audubon Society of Western PA at the observation area on the Great Allegheny Passage Bike Trail on July 4 from 10:00 am until 1:00 pm. They’ll have binoculars and spotting scopes on hand for you to see the eagles. Check their Facebook page for more information.
Click here for a map showing how to get there. –> Park near the Glenwood Bridge at Sandcastle’s back lot and walk less than half a mile on the bike trail.
It was hot and breezy last Saturday when Glenn Przyborski went down to the Great Allegheny Passage bike trail to see the bald eagles’ nest at Hays.
Glenn is a cinematographer so of course he took his camera and a really good scope. His resulting video is a gorgeous, intimate look at the bald eagle family and their nestling who’s due to fledge near the end of this month.
Just because the red-tailed hawks didn’t nest this year on the Panther Hollow Bridge doesn’t mean they didn’t nest at all. This year they’re over by the golf course, a short flight from the bridge but conceptually far for us land mammals who must walk or drive around the Phipps Run valley.
Gregg Diskin photographed the family at their nest this weekend. One of the two babies is already stretching his wings. Click on the image above to see more baby pictures.
A few weeks ago Gregg also photographed one of the adults gathering food … really weird food … pizza.
I remember seeing that pizza at the Westinghouse picnic shelter as I walked to work one morning. The picnickers had carefully put the pizza in the garbage but the raccoons had pulled it out and scattered it. Lots of it! I put it in the garbage again.
The hawk found the pizza long before I did. I’m amazed he picked up a slice and carried it to a light pole.
The Pittsburgh Parks Conservancy’s wetland restoration at Schenley pond has gone so well that a red-winged blackbird has decided to nest there.
Though I haven’t seen his mate there must be a nest because he defends the area from all potential threats. Yesterday morning I was pleased to see a second vote for the wetland when he had to chase off the competition — another male red-winged blackbird.
Shortly thereafter one of the resident red-tailed hawks flew in to perch on a dead snag. Mr. Red-wing was on him right away!
Though I didn’t record this video, it shows exactly what happened. The blackbird perched above the hawk, shouting and flashing his red epaulettes. He repeatedly dive-bombed the hawk and pecked its back.
At first I thought the red-tail would ignore the red-wing but he could not be ignored. The hawk whined and flew to shelter under the roadbed of the Panther Hollow Bridge.
Persistence pays off. In the match-up between Red Wing and Red Tail the blackbird wins.
(video on YouTube from Illinois’ Lake County Forest Preserve District)
p.s. The red-tailed hawk in this video is a juvenile so he whines a lot more than the adult at Schenley Park yesterday.
With orange eyes, fluffy down, and an enormous beak this baby made her media debut yesterday.
She’s the only Eurasian eagle owl to be born in an AZA accredited zoo in the last five years. Hatched on March 13, she lives at the National Aviary where her very versatile mom is an education bird, an exhibit bird and now a breeding bird.
Right now this baby is halfway grown up. She’s cute but gawky, proudly displaying her tawny down. I love her eyelashes. Look at those feet!
You can see her for yourself at the National Aviary starting today, April 10, through May 24. Since she’s just a baby she’ll stay behind the scenes most of the time and come out just twice a day — at 11:45am and 2:15pm.
Watch her grow and change in the next six weeks. By May 24 she’ll look like this.
A new study on the future of climate change in arctic Alaska spells bad news for gyrfalcons in the U.S.
By 2050 the mean annual temperature in northernmost Alaska is expected to rise 3.10C (5.560F). This will usher in a host of changes to ice, coastlines, tundra, plants and animals. What will happen to the area’s breeding birds?
Scientists from the Wildlife Conservation Society, assisted by experts on each species, assessed the future of 54 of arctic Alaska’s breeding birds. The goal was to prepare wildlife and land managers for climate change and ultimately develop plans to mitigate the effects if possible.
The study found that two species, gyrfalcons and common eiders, are highly vulnerable to the anticipated warming and likely to experience dangerous declines. Seven others are moderately vulnerable: brant, Steller’s eider, pomerine jaeger, yellow-billed loon, buff-breasted sandpiper, red phalarope and ruddy turnstone.
Gyrfalcons are specialists and climate change is going to be rough on their niche.
They nest on coastal cliffs in microclimates that are a rare commodity in northern Alaska. South-facing cliffs may become too hot, limiting the number of suitable nest sites.
At the start of breeding gyrfalcons eat ptarmigan almost exclusively. When ptarmigan populations are low gyrfalcons won’t breed at all. When climate change affects ptarmigans it will hurt gyrfalcons.
The gyrfalcon’s hunting style relies on open tundra but as the arctic warms shrubs will grow in formerly open land.
Spring storms are expected to increase. Unfortunately this will cause nest failure for gyrfalcons who require dry weather to hatch their eggs.
With all these cards stacked against them gyrfalcon numbers are expected to drop considerably from today’s 250 breeding pairs.
But the report has a silver lining. There will be more seed eaters: savannah sparrows, Lapland longspurs, white-crowned sparrows, American tree-sparrows and common redpolls.
Much as I like redpolls, I don’t want to trade them for gyrfalcons.
(photo from Wikimedia Commons. Click on the caption to see the original.)
p.s. The report was careful to point out that the study only applies to arctic Alaska, not to all breeding ranges. The photo above was taken in western Greenland.
Here’s something you don’t see every day: two adult Coopers hawks perched near each other.
Coopers hawks are notoriously solitary birds. In winter we may see one hunting near our feeders, but never two. They don’t like others nearby. They chase them off or leave.
But now it’s breeding season and they have to find a mate.
Steve Valasek saw these two at Rio Rancho, New Mexico.
Last week after continuous red-tail dive-bombing and harassment the eagles relinquished the nest to the hawks. There was a brief period of calm, then the eagles fought back.
On Sunday Steve Gosser captured their battle and posted it on Facebook’s Bald Eagles in Western Pennsylvania page. In a few hours his photo was shared more than 460 times.
Harmar Bald Eagle carrying nesting material (photo by Steve Gosser)
11 March 2013:
Bald eagles are the talk of the town in Pittsburgh right now.
This month a nesting pair attracted attention at the Allegheny River in Harmar Township. Steve Gosser photographed of one of them carrying nesting material yesterday.
Last month a bald eagle nest was confirmed at the Monongahela River in Pittsburgh’s Hays Woods. Tom Moeller captured the pair in a morning conversation on March 5.
Bald eagle pair at Hays, Pittsburgh, 2013 (photo by Tom Moeller)
The bald eagle’s return to Pittsburgh was a long time coming. Their population crashed because of DDT and they’d been gone for decades because of water pollution. In the 1970s the U.S. banned DDT and passed the Clean Water Act. In the meantime Allegheny County’s economy changed away from heavy industry. The law and the economy together improved our water quality so that fish, the bald eagles’ favorite food, returned in good numbers.
The Hays Woods site in the City of Pittsburgh is a case in point. Eagles could not have nested there until a whole host of economic and environmental changes occurred. I know the challenges the site has faced. It has taken 30 years.
Thirty years ago (1983) the Homestead steel mill closed due to economic issues. Only a mile upstream from the eagles’ nest, that closure brought better air and water quality to Hays. Fish increased in the Monongahela River.
Fifteen years ago (1998) LTV closed the Hazelwood coke plant across the river, another economic decision. Air quality improved and the river returned to its normal temperature. Fish increased because the plant no longer dumped hot water into the Mon.
Ten years ago (2003) a developer planned to strip mine and valley-fill Hays Woods to build a race track and casino. The Save Hays Woods Coalition formed to fight this plan and protect the 635-acre site.
Three years ago (2010) legal wrangling over the strip mine finally came to an end.
Every bald eagle nest in western Pennsylvania has a story of recovery. Thanks to the bittersweet end of heavy industry, dedicated environmental heroes, and the resilience of nature our national bird is back in town.
(photo of Harmar eagle with nesting material by Steve Gosser, photo of Hays eagle pair by Tom Moeller)
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