This morning just after dawn I saw a peregrine fly by my window carrying prey to the Cathedral of Learning. I’m sure it was Ecco bringing breakfast to Carla. The pair is “in tune” as if it was nesting season. Ecco supplies Carla’s food and they bow at the nest several times a day, but I know there will be no eggs at the Cathedral of Learning this year. It’s too late to raise a peregrine family.
Today on Throwback Thursday I looked back seven years to find that the blog was All Peregrines All The Time in 2016. In this trip down memory lane, you might remember a few of these incidents from that June.
A moment of repose: Peregrine fledgling C1, 16 June 2016 (photo by Peter Bell)
One week later a banded female peregrine showed up on camera at the Cathedral of Learning nest. It was Magnum from the Neville Island I-79 Bridge territory where she had already fledged two young. (Click here or on the video screenshot for the story.)
A few days later Magnum left Oakland, Hope and Terzo paired again, and their fledgling grew up and left town.
This year, by contrast, is very quiet. Fingers crossed for a good season next year.
Sunrise on the summer solstice, Pittsburgh, 21 June 2023 (photo by Kate St. John)
Wednesday 21 June 2023
Two days ago we learned how humans are changing the tilt of the Earth(*). Today we celebrate the most important Tilted Earth Day in the northern hemisphere when the summer solstice occurs at 10:57am EDT and gives us the longest day.
Three years ago meteorologist Bill Kelly made this video at WJLA in Washington, DC explaining how the Earth’s tilt is the key to the solstice. Only one fact has changed: The solstice is on a different date and time. Sunrise, sunset, and day length are the same in DC today as they were on the solstice in 2020.
In Pittsburgh today the sun rose at 5:49am, we’ll have 15 hours, 3 minutes and 50 seconds of daylight, and the sun will set at 8:53pm. Thanks to the tilted Earth.
(*) p.s. How much have humans changed the tilt of the Earth? The study highlighted in Monday’s blog calculated that we’ve already moved it 80 cm (31.5?) in just 17 years (1993-2010). Click here to read more.
(photo and video credits: Click on the captions to see the originals)
Occasionally during the May-to-August storm season, the National Weather Service warns of flash flooding because of potential “training thunderstorms.”
Training thunderstorms? Are they getting in shape for a big competition? Are they practicing to be better thunderstorms? Are they learning from older, wiser storms?
No. “Training” in this case means the storms are lined up in a row, moving one after the other like railcars in a train. The Philadelphia Area Weather Book describes it:
Most of the year, thunderstorms, steered by speedy winds a few miles above the ground, move along quickly enough so that flooding is not a problem. But those high-altitude winds are typically much weaker in summer and, at times, nearly calm. When this happens, thunderstorms can sit over the same spot for hours. Even if the steering winds are not that lazy, flooding can still occur if the winds blow parallel to a line of storms. When that happens, one thunderstorm after another passes over the same location like railroad cars in a train passing over a track. Appropriately meteorologists call this process training.
When radar-watching meteorologists saw this phenomenon they turned the concept of “moving like a train” into an adjective describing thunderstorm behavior. The new use of an old word did not catch on. Though it’s been around at least 30 years it’s not in the dictionary.
Compared to the size of our planet we humans aren’t particularly large but with billions of us pumping groundwater we have changed the tilt of the Earth. Slightly.
The angle of Earth’s axial tilt varies over a period of 26,000 years (precession) from 22.1 to 24.5 degrees, but within that it wobbles due to sloshing liquids like molten lava, ocean currents, and massive air currents such as hurricanes.
This very short video shows the North Pole wandering as the axis wobbles.
Earth’s spin axis wobbles, its North Pole tracing out a roughly 10-meter-wide circle every year or so. The center of this wobble also drifts over the long term; lately, it has been tilting in the direction of Iceland by about 9 centimeters per year. …
Now, scientists have found that a significant amount of the polar drift results from human activity: pumping groundwater for drinking and irrigation.
To find out what affected Earth’s axial tilt, Clark R. Wilson at the University of Texas at Austin and his colleagues built a model of polar wander factoring in all the sloshing over time, including changes to surface water. But the model was missing something.
When the researchers also put in 2150 gigatons of groundwater that hydrologic models estimate were pumped between 1993 and 2010, the predicted polar motion aligned much more closely with observations. Wilson and his colleagues conclude that the redistribution of that water weight to the world’s oceans has caused Earth’s poles to shift nearly 80 centimeters during that time, reported Thursday in Geophysical Research Letters.
The GRACE satellites detected groundwater changes that produced this map. Notice how groundwater dropped in the U.S. Southeast and the Central Valley of California.
When I began watching peregrine falcons 22 years ago, peregrines were endangered and our smallest falcon, the American kestrel, was doing just fine, but the tables have turned. Peregrines have fully recovered from extinction in eastern North America while kestrels have lost half their population and face an uncertain future. The New York Times described their plight this week in The Mystery of the Vanishing Kestrels: What’s Happening to This Flashy Falcon? Can we save this beautiful bird before it’s gone?
American kestrels are versatile birds. At home in grasslands, meadows, deserts, cities and suburbs, they eat grasshoppers, crickets, large flying insects, beetles, lizards, small rodents and small birds.
Kestrels nest in cavities in buildings, trees, cliffs and nestboxes but more than half of their sites are unoccupied now in eastern North America. I’ve seen the decline first hand in Pittsburgh. A decade ago there were two kestrel nests within a few blocks of Downtown’s Third Avenue peregrines. Now there are none.
Dr. John Smallwood, a professor of biology at Montclair State University interviewed in the New York Times article, has monitored 100 kestrel nestboxes in New Jersey for nearly 30 years. The number of occupied nests at his sites peaked at 61 in 2002 and has dropped ever since.
What’s going wrong for kestrels? Are they out-competed for prey? Are they ingesting poison? What’s happening on their wintering grounds? Are insect declines affecting kestrels? Are neonicotinoid pesticides a factor? And what about the bigger questions of habitat and climate change?
Many kestrel experts think it’s a combination of causes. Dr. Smallwood agrees, but he still has a top suspect. “If I’m only allowed one word: grasshoppers.”
The one parameter that seems to be declining over time, researchers say, is survival of young birds in the summer.
… the thinking is that those juveniles may be more dependent on insect prey because it’s easier to catch.
Meanwhile a nationwide study funded by the USGS and the U.S. Fish and Wildlife Service is looking into the American kestrel’s mysterious decline. I hope they find the answer soon.
In North America we call our smallest falcon a “kestrel” (Falco sparverius) because it resembles the well known Eurasian or common kestrel (Falco tinnunculus) in Europe. Both are cavity nesters that use holes in cliffs, trees or buildings.
Wildlife artist and blogger Robert E Fuller (@RobertEFuller) has live nest cameras at his farm in Yorkshire, England including two on common kestrel nests. When he tweeted this video three days ago the eggs in Jeff and Jenny’s nest were about to hatch. Yesterday the first three hatched. Today the chicks are growing fast and the last egg awaits.
Now that it’s insect season we’re back to swatting flies, but are we successful? Mostly not. Flies are masters at avoiding swats for a couple of reasons.
First, they have much faster perception and reaction times than we do. Back in 2008 researchers at Caltech used high speed, high definition video to record the movements of fruit flies avoiding a swat threat. Amazingly, flies can react to an approaching swatter within 100 milliseconds.
Second, the flies’ middle legs are key to their escape. When a fly sees a threat it re-positions its body, sets its long middle legs in the right location, and pushes off from them.
The photo series below from the Caltech study shows a fruit fly perceiving a threat from the front (right side of photos) with red dots indicating the original location of the fly’s middle legs. At 215 milliseconds the fly has its middle legs in launch position. When it jumps at 287 milliseconds (the last possible moment) it’s using its middle legs.
Fly science hasn’t changed that much since the first discovery 15 years ago but the explanation of fly reaction time has gotten better as shown in this video.
We humans move, see, and think slowly compared to a fly but if we can anticipate where the fly will jump and aim for that spot we stand a chance of nabbing it.
Once a year, from late June until August, Canada geese spend six weeks molting all their wing feathers. This means they can’t fly in July, nor even in late June.
On a walk at Herrs Island yesterday I saw many Canada geese swimming in the river and a few of their primary feathers — the “fingertip” feathers — scattered on shore. At first I wondered if a goose had been attacked and then I realized the feathers were a sign of their synchronous molt. Here’s a snapshot from a similar discovery made by Rebecca Johnson in 2020. (Click on the snapshot to see her video on YouTube.)
Even if you don’t see discarded wing feathers you can tell a Canada goose is molting because its white rump is visible above the dark tail. It’s really noticeable from above.
In late June and July when they cannot fly Canada geese are safe only in water. You’ll see them feeding just a short walk from a large body of water and notably absent from landlocked places.
When they can fly again, their tails will look like this when their wings are closed.
