Is a flock of 15,000 crows a burden or an opportunity? At the University of Washington, Bothell it's an opportunity for a groundbreaking study on crow communication.
Every year from fall to spring, 15,000 crows gather on campus on the way to their roost in the North Creek Wetlands. These gatherings are their noisiest time of day.
Crows are intelligent so chances are good that they're saying something meaningful -- but no one knows what it is.
Last year UW Bothell biologist Douglas Wacker and acoustics expert Shima Abadi decided to team up and find out. Working with a group of students, they tested audio equipment and the crows' reactions to it. They also wrote software to find the most interesting parts of the crow conversations so researchers don't have to wade through hours of recorded caws to find the best parts.
Setting up the equipment was not as simple as you'd think. Crows are wary of changes in their surroundings so audio equipment was introduced carefully on the rooftop of Discovery Hall, a building where the crows congregate. By the time this photo was taken, the crows were cool with four audio rigs on the roof.
This winter Wacker, Abadi and their team of students will learn more about crow communication and pair it with video to determine who's saying what.
Tonight is the night of the Supermoon, a full moon at perigee that looks 14% bigger and 30% brighter than normal.
What will you see by moonlight on Pitt's campus tonight, clustered at the treetops like large black leaves?
Thousands of crows.
Despite the weird scarecrow sounds played from the buildings, Pittsburgh's winter crow flock continues to roost in the mature trees surrounding the Cathedral of Learning and Heinz Chapel.
On Friday I tried to count them by the light of the moon. They were clustered in 30 trees and on the roof of Carnegie Museum. The densest trees held 300 crows.
Could there really be 9,000 crows in the area of Forbes, Fifth, Bellefield and Bigelow Avenues? Maybe I over counted. Last year I estimated 230 crows per tree making this total 6,900 crows on December 1 at 6:15pm.
What is their fascination with the University of Pittsburgh? It isn't the buildings. It isn't the lawn. It's the well lit trees.
Crows prefer to roost where they can see danger coming. The campus is well lit for our protection. The crows like it, too.
Alumni Hall is a good vantage point for watching crows and the moon rise next to Heinz Chapel.
Stop by this evening to see it all by the light of the supermoon.
This week pedestrians near the Cathedral of Learning are hearing weird scary bird sounds after sunset. Yale Cohen recorded them on Wednesday and asked, "What is this?"
The recording sounds like a bird in distress followed by rapid peregrine "kakking." It's an audio scarecrow.
Pittsburgh's winter crow flock has decided to roost in Oakland bringing at least 4,000 crows into the trees on campus. Every morning the sidewalks are a gooey smelly mess. Here's what the Fifth Avenue sidewalk looked like on November 14 (photo by Claire Staples).
In 2013 the recordings worked, The Crows Moved, but this time they haven't gone so far. Michelle Kienholz texted me on Wednesday:
Pitt aggressive bird sounds screaming out at different locations in sequence. Crows settling elsewhere but still on campus.
I've found crow evidence below the London plane trees by Carnegie Library, the Pittsburgh Public Schools office and St. Nicholas Cathedral. The crows have moved -- but only across the street.
They've already figured out the scarecrow. It's annoyingly loud but not scary.
p.s. Why does the flock like to roost at Pitt? Look how well lit the area is at night (photo at top)! Crows like to sleep in tall trees where the lights are on.
(credits: Cathedral of Learning at night from Wikimedia Commons; click on the image to see the original. Messy sidewalk by Claire Staples. Audio recording by Yale Cohen)
The black silhouettes in this tree near the Cathedral of Learning are not leaves. They're crows.
Pittsburgh's crow population has swelled since the weather turned cold last weekend. On Monday I counted 4,000 flying into Oakland from the south, pausing on the roof of Carnegie Museum before heading to their final destination.
I couldn't even see the crows arriving from east, west and north but distant trees at Schenley Farms were coated with crows and hundreds, perhaps thousands, gathered on the rooftops north of Fifth Avenue. My cellphone barely captured a look at them as night was falling.
Where did they roost? I didn't stay long enough to find out, but they left their evidence behind.
On Tuesday Claire Staples sent me photos from St. Paul's Cathedral on Fifth Avenue. The crows left a mess on the wall and sidewalk below the stately London plane trees.
For now the crows are roosting near Fifth Ave and Craig Street but that will change. They're wearing out their welcome.
Tuesday evening (October 23) Michelle Kienholz sent me the photo below of a huge flock of crows flying over Schenley Park toward CMU at 6pm. See those specks above the horizon? Hundreds of them!
Yes, it's late October and the crows are back in Pittsburgh for the winter. This is just the beginning of the flock. More will follow.
In the next few weeks the crows will move their roost several times until they settle on a favorite safe place. Meanwhile, you'll see them at dawn and dusk flying down the Allegheny River valley and through Oakland.
In this video from India, see the house crows (Corvus splendens) use their slotted wings to stay aloft in the strong wind. Someone off camera is tossing bread in the air. The crows hover and flap to catch it.
Slotted wings save energy as the crow flies.
It looks like fun.
p.s. Test your skills at identifying birds in flight. Find a pigeon (or three) that parachutes in to join the flock. How can you tell it's a pigeon? Pigeons have pointed wings.
It doesn't make sense but if your wings are the right shape flapping saves energy.
Birds and airplanes must constantly overcome drag to stay aloft. One source of induced drag occurs during lift when swirls of air, called vortices, roll off the wingtips. This small plane generates a huge wingtip vortex, forcing it to burn more fuel as it flies.
Large soaring birds, such as turkey vultures, reduce drag in two ways. Their wingtip feathers form slots that break the single vortex into smaller ones (small is good!), and they turn their wingtips up as they soar.
Southwest Airlines turns up its wingtips, too, to save fuel.
But what about smaller birds that flap all the time? Are they doomed to inefficient, labor-intensive flight? A new study from Sweden says no.
Biologists at Lund University studied jackdaws (Corvus monedula), a corvid smaller than the American crow. Using mist and multiple cameras they found that the birds' slotted feathers, specifically designed for flapping flight, also break up the vortex into multiple swirls. See them rolling off the wings in the study photo at top.
Now that we know slots are efficient for both flapping and soaring, what prompted their development? The study's authors "propose the hypothesis that slotted wings evolved initially to improve performance in powered (i.e. flapping) flight."
In fact, flapping saves so much energy that author Anders Hedenström suggests, "We could potentially build more efficient drones to fly with active wingbeats. Within a ten-year period, we could see drones which have the morphology of a jackdaw."