Both studies correlated the annual mean summer temperature of the species’ breeding range and reached the same conclusion: As the climate heats up, birds are getting smaller.
We should expect this.
There’s a biological rule of thumb called Bergmann’s Rule which states that, within a species, populations living in colder climates have larger body size than those in warmer climates. Bergmann’s explanation is that large animals have a lower surface-area-to-volume ratio so they lose heat more slowly in cold climates while small animals have a higher surface-to-volume ratio and can cool off faster when it’s hot.
Song sparrows (Melospiza melodia) provide a good example of Bergmann’s rule because they range across North America from Alaska to Newfoundland and south to Mexico. I saw their variability up close in the Carnegie Museum of Natural History’s Section of Birds in December 2016. My photo below shows sparrows collected in Alaska in the top row, sparrows from Pennsylvania on the bottom.
Here’s a closeup placed side by side (below):
On the left, two song sparrows collected in Pennsylvania: Pittsburgh (leftmost) and Geneva Marsh.
On the right, song sparrows collected in Alaska’s Aleutian Islands at Unalaska (leftmost) and Sanak.
Alaskan song sparrows are so large that they have to be placed sideways in the tray!
Smaller size is normal where it’s warmer.
It isn’t bad news for birds and it tells us two additional things:
Birds’ bodies have been registering climate change long before we humans noticed or admitted it.
Here are two seaside bird cams to watch while we wait for Pittsburgh’s eagles and peregrines to lay eggs in the coming months.
Above, a northern royal albatross (Diomedea sanfordi) couple nests on camera at Taiaroa Head Nature Reserve in New Zealand. The pair have lots of combined experience — he’s 21 years old, she’s 25 — so they know their egg, laid in Nov 2019, is due to hatch at the end of this month (January 2020).
Since New Zealand is 18 hours ahead of Pittsburgh it’s best to watch from noon to midnight Eastern Time if you want to see the birds in daylight. This is a perfect schedule if want to kickback at the end of the day. See the northern royal albatrosses at their nest on Cornell Lab’s Royal Albatross bird cam.
Just one time zone ahead of Pittsburgh, the female Bermuda cahow (Pterodroma cahow) rejoined her mate at their nest on Nonesuch Island, Bermuda on 10 January 2020. Almost immediately she laid her single egg. Watch their reunion in this short video.
The amazing photo below of an eagle’s claw and a human hand left me wondering, Who is this bird and why are his claws so big? Today I’ll tell you a bit of his life story.
Shaped like a giant goshawk with a feather crest, the crowned eagle (Stephanoaetus coronatus) lives in the riparian forests of sub-Saharan Africa where it eats monkeys, small forest antelopes (duikers), “mouse-deer” (chevrotains) and “rock rabbits” (rock hyrax). Click on the links to see photos of these unusual animals.
Crowned eagles weigh only 6-10 pounds, smaller than bald eagles, yet they routinely capture mammals twice as heavy as they are. Reports say they can fly with prey that outweighs them, but they normally rip it apart on the ground and cache pieces in the trees. For this lifestyle they need large talons.
For thousands of years people have known that certain sand dunes make a low humming sound, the musical note of G, E or F. It occurs when the sand is moving but you can force the sound if you slide downhill. Why does it hum?
A decade ago scientists at CalTech studied two humming sand dunes in California to answer that question. They found that for the sand to sing, the grains have to be all the same size, the dune must have a slope greater than 30 degrees and be over 120 feet tall, and the sand must be dried under the desert’s summer sun. It was very hot work.
The humming sound occurs naturally when the sand moves but that doesn’t happen on a predictable schedule so the CalTech team forced the sound. Dr. Melany Hunt explained,
Usually we would trigger it by having a number of people slide down the dune in unison. We always called it ‘Science by the seat of our pants.’
This month’s trip to Cape Cod provided me with a brief change of scene and a brief change of birds. On October 18 and 19, local photographer Bob Kroeger showed me many of his favorite birding spots. Here are some of the birds we saw, with thanks to Bob for the photos.
Sanderlings (Calidris alba) never come to Pittsburgh but they spend the winter at Cape Cod. It was fun to see them poking the sand with their beaks and bathing at the water’s edge at Corporation Beach.
Ruddy turnstones (Arenaria interpres) are an extremely rare bird in Pittsburgh that also winters at Cape Cod. They aren’t ruddy in the fall, but their legs are still orange.
Great blue herons (Ardea herodias) were plentiful in the marshes. They’re huge in flight!
We found one or two blackpoll warblers (Setophaga striata) at nearly every place we stopped. This one at Long Pasture still has hints of black on his face and the telltale yellow feet. They are on their way to Brazil.
We found a flock of 25 palm warblers (Setophaga palmarum) at Cape Cod Organic Farm, all of them the duller western birds. In mild winters palm warblers stay on the Cape.
Most plentiful by far were the “myrtle” yellow-rumped warblers (Setophaga coronata) who’ve come to stay for the season. The winter birds look dull but in Bob’s closeup below you can see his feather details.
Best only-at-the-sea birds: At Wellfleet Bay on the 21st I saw distant flocks of 200 brant (Branta bernicla) and 60 common eider (Somateria mollissima).
Best mammal : A coyote crossing the road near Monomoy.
Craziest bird: A wild turkey running non-stop around a parked car in Harwich, like this. I’m waiting for the day I see this in Pittsburgh. 😉
Travel is a tonic for seeing the world in new ways. This month my husband and I spent a week with his sister at Cape Cod where we had new weather, new scenery and new looks at plants I might have seen at home.
Our timing was pretty good. We missed the October 12 nor’easter but were on hand for the October 17 “bomb cyclone.” We didn’t lose power, but it was still very windy on the 18th when I visited Fort Hill, pictured above.
Birds were hard to find that day so I noticed plants such as this European spindle-tree (Euonymous europaeus) with puffy, pink, four-sided fruits.
The puffballs are actually a casing that holds orange fruit within. This ornamental has probably been planted in Pittsburgh, though I’ve never noticed it.
My favorite discovery was a hole in a leaf.
Who ate it? Perhaps this caterpillar did. I found him elsewhere on the plant.
And finally, the sun touched translucent red berries and made them glow at Bell’s Neck.
The small plants have a single leaf midway up the stem (lefthand photo) and were growing among pine needles. Please leave a comment to tell me what they are.
p.s. Thank you to Kerry Givens who identified the red berries as a Canada mayflower and the caterpillar as a Turbulent Phosphila moth.
(photos by Kate St. John except where noted in the captions; click the captions to see the originals)
The intense wildfires in Alaska this summer are different than those we’re used to in the Lower 48. These were sparked by unusual weather, they’re harder to put out because the soil is burning, and they’re causing their own feedback loop.
When lightning starts a fire in the boreal forest or tundra it doesn’t just burn trees and shrubs. It also burns below the surface because the soil is like peat moss. These “underground” fires are extremely hard to put out.
And finally, the fires cause their own feedback loop. They’re generated by unusually hot weather and their byproducts — smoke and CO2 — result in more hot weather. The smoke deposits black soot on polar ice which makes it melt faster (warming the area) and the CO2 contributes to climate change. As the climate gets hotter it spawns more arctic fires.
This 13 August video from NASA tells more about the arctic wildfires and how they’ll affect us — both now and later.
Late last month observers discovered a small green pond at the bottom of Halema’uma’u Crater at Kilauea volcano. Water inside the crater is rather amazing since Kilauea is the active volcano on the Big Island of Hawai’i that erupted violently in 2018, destroying parts of Leilani Estates, Highway 132, Vacationland and Kapoho.
Geologists wondered if the green spot was a rock or algae so they flew over the crater several times looking for a telltale reflection to indicate it was water. Yes, it’s wet.
Bristle-thighed curlews are so rare and hard to find that they’ve been called the birders’ Holy Grail. The word “Tahiti” in their scientific name, Numenius tahitiensis, tells us why. These birds are Pacific Islanders. Their remote breeding location in Alaska was not discovered until 1948.
Adult bristle-thighed curlews spend only two months on their breeding grounds at the central Seward Peninsula and Yukon Delta. They arrive in late May and begin nesting almost immediately.
When the eggs hatch in June, the chicks are precocial and soon walk off the nest.
At 3+ weeks old they learn to fly but they aren’t independent yet. At 5 weeks their parents leave them with a few caretaker adults and depart for the staging grounds at the Bering Sea.
There they fatten up for the first leg of their journey home — a non-stop 2,500 mile flight to Laysan, Midway Atoll in the Hawaiian islands. For some curlews the final destination is much further, as shown on the map below. (Red spots are breeding range, white arrow is first stop, blue circles are wintering locations.)
Young curlews follow the adults a few weeks later. They won’t return to Alaska until they’re three to four years old.
This year I happened to visit Hawaii and Alaska on the same schedule as the bristle-thighed curlews. My Life Bird curlew was a fly-by at Kahuku Golf Course, Kauai on February 28, photographed here by Michael McNulty. Then I saw curlews on their breeding grounds near Nome, Alaska in June.
Every year the curlews travel from Hawaii to Alaska. With a worldwide population of only 7,000 birds and sea level rise due to flood their home islands, this amazing bird is vulnerable to extinction.
p.s. Bristle-thighed curlews are closely related to whimbrels, whom they resemble. We saw and heard both species in western Alaska.