The males pump their heads, raise their crests, toss their heads forward as if to unfurl their hoods, and waggle their heads side to side. “Look at my white crest!”
They also throw their heads back and point their beaks to the sky. As they bring their heads upright they say “Merg-merrrrrg!” Listen to the video. They sound like frogs!
So why does the hooded merganser have a hood? Relentless female selection. The ladies are so impressed by a good head toss that they pick the guys with the biggest, whitest hoods. The guys with little hoods never have kids.
This month while the ducks are stalled in Pennsylvania waiting for northern lakes to thaw, they spend their time courting. Some species merely chase the ladies. Others have elaborate displays. My favorite is the common goldeneye who tosses his head so far back it looks as if he’ll hurt his neck.
In this video two male goldeneyes (blue-black iridescent heads with white face patches) show off for two females (brown heads). The males raise or lower their head feathers to make their heads look round or flat. When they toss their heads their feathers are raised and their heads look enormous. The gesture is not enough. They also make a rattling peent, “Look at me!”
If the lady likes what she sees she swims with head and neck outstretched as if she’s dipping her neck in the water. This suggests her posture during copulation so if course it keeps the action going.
“Do that again,” she says, “Toss your head for me.”
In this video of the egg’s first on-camera appearance notice the reactions of ‘Ma’ and ‘Pa’ eagle…
The video begins with the mother eagle standing over her egg, waiting for it to dry. Her tail is spread and she’s holding her wings open to shelter the egg without touching it.
When the egg is dry, she gently rolls it with her beak and keeps her talons folded in as she steps near the egg. She is very careful.
Just before her mate arrives you can hear his “whee” call announcing his arrival.
Notice how much bigger the female is than her mate. This size difference is normal in birds of prey.
Both eagle parents rearrange the sticks, mosses and grasses in the nest. If you watch peregrine falconcams you’ll notice that peregrines don’t use sticks so there’s nothing to adjust. Watch closely and you’ll see peregrines rearrange the rocks.
Though the eagles are nesting on an extensive wooded hillside above the Monongahela River, the river banks hosts two active railroad tracks and a scrapyard. That’s why you hear mechanical and industrial sounds on the camera.
You can watch the eaglecam at several websites. My two favorites are PixController and the National Aviary. Click on a logo below to watch the Pittsburgh eaglecam. PixController’s has a link to the video archives.
As you saw last weekend there are still crowds of bald eagles gathered along North America’s rivers waiting for winter to end. They can’t go home and begin courting until the ice breaks up.
Meanwhile Pittsburgh’s eagles have a head start on the nesting season because our rivers don’t freeze over. The pair at Hays has already progressed to the finer points of nest construction. They finished the foundation (large sticks) and the bowl (small sticks) and are now working on the nest lining (soft grasses). Sometimes they bring a fish and have a snack at the nest. When the lining is complete, egg-laying won’t be far away.
When you watch the Pittsburgh Hays eaglecam you’ll notice how different eagles’ habits are from peregrines’ behavior. Peregrines don’t “build” a nest, they never use sticks or soft grasses, and they almost never eat at the nest unless they have young in it. This difference is driven by their food and habitat needs: bald eagles eat fish and nest in trees near water, peregrines hunt birds on the wing and nest on cliff ledges.
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.)
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.)
Why do peregrines nest on buildings and bridges instead of cliffs?
“Raptors imprint on their natal nest sites. Consequently, they choose a similar situation several years later when they reach maturity.”(1)
This explains why they’ve chosen to nest at the Tarentum Bridge, pictured above. The adult female, nicknamed Hope, was born on the Benjamin Harrison Bridge in Hopewell, Virginia. That bridge is such a dangerous place to fledge that Hope was hacked in the Shenandoah Mountains, but she remembered where she was born and picked a bridge when she chose a place to nest.
There are exceptions to the natal imprint rule. Though Dorothy’s daughter Maddy was born on the Cathedral of Learning, a 40-story Late-Gothic Revival building, she chose the I-480 Bridge in Valley View, Ohio. I can’t think of anything less like the Cathedral of Learning than this. (The nest is at a broken patch of concrete on the bridge support.)
The exceptions have saved at least one species from extinction.
Mauritius kestrels used to nest in tree cavities but monkeys were introduced to the island and ate the eggs and young. By the 1960′s the kestrels were down to two pairs — almost extinct — when one of the pairs decided to nest on a cliff ledge where the monkeys couldn’t reach them. That nest was successful, their youngsters nested on cliffs, and the species rebounded.
The exceptions benefit the rule.
(photo of Hope at the Tarentum Bridge (blue structure) by Sean Dicer. Photo of Maddy’s nest site at the I-480 Bridge at Valley View (busy highway) by Chad+Chris Saladin.
Today’s Tenth Page is inspired by and includes a quote(1) from page 444 of Ornithology by Frank B. Gill.)
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.
A week ago on May 23 Chris Rolinson set up his time-lapse camera at Point Park University’s Lawrence Hall to capture snapshots of the Downtown peregrines. My favorite is this one of Dori leaving the nest and Louie coming in. Awesome wing action! Look at the chicks watch and call.
Chris also created a video from the time-lapse snapshots. Click on the photo to watch a quick day in the life of six peregrines.