I heard my first wood thrush this year in Schenley Park on April 24 but the real influx didn’t occur until May 8. On that morning the wood thrush population in the park doubled overnight.
Each bird made the trip from eastern Honduras or Nicaragua in 13-15 days. Thanks to ongoing migration studies by Bridget Stutchbury’s University of York team, we now know where wood thrushes spend the winter, how long it takes to get here, and the routes that individual birds take.
Stutchbury pioneered the use of tiny geolocators, smaller than a penny, that record only two things: the universal date-time (UTC) and the amount of light. Crunch a year of data and you get sunrise, sunset and day length which reveal the bird’s location each day. To collect this data, the tagged bird had to return from migration (a 60% chance) and be re-trapped to remove the geolocator (90% success rate, skill required!).
Now that the team has tracked some individual wood thrushes for several years they’ve found that:
- Wood thrushes fly more than 300 miles a day on migration.
- In the fall, they may stopover in the southern U.S. or the Yucatan for one to four weeks before proceeding to their final destination.
- They dawdle in the fall but return two to six times faster in the spring because they barely stop at all.
- Wood thrushes who live near each other in Pennsylvania don’t scatter when they get to Central America. A single breeding population from Pennsylvania spends the winter in a narrow band of forest in eastern Honduras and Nicaragua. If that forest disappears, so will all those wood thrushes.
- Wood thrushes don’t use local weather cues to determine when to head north. Instead they have built in endogenous triggers similar to long-distance shorebirds. Some of their triggers are so accurate that individuals begin northward migration on the same day every year.
- Though wood thrushes tend to have a favorite departure date they don’t take the same route every year. The route depends on weather and fitness.
- First year birds tend to leave the wintering grounds later than those who’ve made the trip before.
So I’ll bet those early wood thrushes are the older, experienced birds who left Central America around April 10. Two weeks and more than 2,000 miles later they arrived in my neighborhood on the day the rest of the flock left the wintering grounds.
For more on these studies, click here for background on the 2010 report and here for their 2012 findings.
(photo by Steve Gosser)
Yesterday morning three peregrine chicks hopped all over the place at the Downtown Pittsburgh nest.
Thanks to Donna Memon for capturing this image at just the right moment!
UPDATE ON THURSDAY MAY 16:
Aha! I love to be proved wrong when the news is happy! There are FOUR chicks in the Downtown nest. Thanks to Nathalie Picard for alerting me. Here’s a screenshot:
(photos from the National Aviary falconcam at Point Park University)
The other day a mourning dove slammed into our bathroom window so hard it made me jump two rooms away. The impact left feathers stuck to the glass and scattered on the roof.
From our backyard feeders the window must look like a safe hole in the sky to escape the local Coopers hawk. But no. That dove probably died.
It wasn’t the first time the two upper windows on the back of our house have been hit but I hope it will be the last. I’ve ordered the thin bird tape shown above at American Bird Conservancy’s Bird Tape website.
I’m hoping for great results. The stripes have got to be better than the dusty outline of a dead dove on my window.
(photo from ABCbirdtape.org. Click on the image to visit the website.)
p.s. On a somber note, I read Lisa Ann Malandrino’s blog yesterday about the dead birds she found near her office in Jersey City on May 10. Window strikes in cities kill many, many birds on migration, a problem much larger than bird tape can solve. We need an organized effort in U.S. cities like the Fatal Light Awareness Program in Toronto, Ontario.
It used to be that wild animals avoided human contact but that’s not true in Pittsburgh anymore. We have hawks, wild turkeys, foxes and deer in the city. Not every animal can cope with city life but the individuals who can tolerate close human approach are doing quite well in our parks and cemeteries.
Sharon Leadbitter visits Allegheny Cemetery often and frequently saw this doe and fawn last summer. They weren’t tame but they learned that Sharon isn’t dangerous. This was reinforced for the fawn every time it met a human and Mom said “It’s ok.”
Fawns are born in May in Pennsylvania so by now this baby is an adult and it’s mother has a new fawn. I’ll bet this doe will let Sharon meet her new fawn, too.
And there will probably be four deer this year. This doe plus her new fawn, and this fawn (now an adult) plus her fawn. That’s how easy it is to end up with a lot of deer.
(photo by Sharon Leadbitter)
Ever since they returned from Peru last month the chimney swifts have been busy courting in the air.
You’ll often see a trio chittering loudly, flying fast, and turning sharply in unison. Studies have shown that the lead bird is usually a female and her followers are male. Their chases last more than five minutes, more time than I usually can spare to watch them.
After they form pairs the couples continue to fly together. Sometimes as they sail by the rear bird will raise his wings in a V. This happens more often after pair formation so scientists believe it’s part of pair bonding. I’ve seen pigeons do it too, without the “chitter.”
Chimney swifts have other amazing flight abilities. Did you know that…
- They fly almost constantly and only stop to roost or nest.
- They bathe on the wing by smacking their bellies against the water’s surface and shaking it off.
- If the opening is wide enough they can fly headfirst into a chimney and turn upright in mid air to cling to the chimney wall.
- They fly into narrow chimneys tail first.
- Their mean air speed is 29-30 miles per hour.
- They can fly at an altitude of 7,000 feet on the warm air rising ahead of a cold front.
It’s a joy to watch a bird that flies so well.
(photo by Jeff Davis)
Dorothy and her chick have been emblematic of mothers’ love this year. Above, Baby leans on Dorothy.
And here Dorothy watches over Baby as he sleeps.
Happy Mothers’ Day to all mothers, and especially to my own mom who reads this blog every day.
(photo from the National Aviary falconcam at University of Pittsburgh)
Violets with amazing colors are blooming now if you know where to look.
Dianne Machesney found these bird’s-foot violets (Viola pedata) at Sideling Hill just south of the Pennsylvania border in Maryland. They prefer dry, undisturbed soil so they don’t do well in gardens where the loamy, moist soil is turned over often.
Above, a close up of the flowers. Below, the entire bouquet shows the birds-foot shaped leaves.
Most of the flowers are one shade of blue. The two-toned blooms are extra special.
(photos by Dianne Machesney)
Matthew Richardson had a visitor on his balcony at Point Park University yesterday.
Who is that bird perched on the railing? Certainly not a robin!
The peregrine preened his back feathers and looked headless for a moment.
Then he stretched…
…and looked at Matthew.
Louie was taking a good long look.
Did you know that when peregrines look at you from a 40 degree angle they’re seeing you with their very best vision?
On Monday I met Chris Saladin who monitors peregrine falcons in Ohio. Chris and I have corresponded in email for years — and you see her photos on this blog — but we had never met. It was great to get to know her!
Chris and I stopped beneath the Ohio Turnpike bridge in Cuyahoga Valley National Park where Rocky and Lara nest. We chatted about peregrines while Rocky flew around and checked his cache zones. Then he perched up high and looked at us obliquely. I knew he was watching us but Chris said, “He’s seeing us really well right now.” From an angle? Here’s why.
Everyone’s eyes have their highest visual acuity at the fovea, the small depression on the retina that holds the highest concentration of receptors and nerves. In humans this is 4-8 degrees off center but in peregrines, it’s at a 40 degree angle from their straight-ahead vision. When they dive on prey they circle downward on a logarithmic path that keeps their highest vision on the prey below.
Chris told me that when a peregrine merely wants to look at you he doesn’t have to face you. When he looks straight on, watch out! Chris had just experienced this with Stammy (Dorothy’s son) in Youngstown after she visited his nest to check on his nestlings. Click here to see Stammy coming straight at Chris.
(photos by Matthew Richardson)
We tend to think that birds with precocial chicks have an easier time as parents than those whose nestlings are naked and blind at birth, but this isn’t necessarily so.
Ducklings can walk, swim and feed themselves shortly after they hatch but their mobility is problematic. They have no idea where to find food nor how to stay safe. All they know is “Stay with Mom!”
Mother leads them to feeding areas and shows them what to taste. The ducklings peck in the vicinity until they find good food.
Her hardest responsibility is protecting them from danger. Baby ducklings are tasty morsels for raptors, minks, cats, dogs, large fish and snapping turtles. If you watch a mallard family day to day you’ll notice the number of ducklings decreases over time. Mom does her best but danger lurks.
This mother mallard has had pretty good success so far. Out of 8 to 13 eggs she still has six chicks.
Until they can fly she has mothers’ work to do.
(photo from Wikimedia Commons. Click on the image to see the original. Today’s Tenth Page is inspired by page 483 of Ornithology by Frank B. Gill.)
Now that the falconcam is running and the peregrine chicks are mobile we’ve been trying to count white, fluffy heads. How many chicks are at the Downtown Pittsburgh peregrine nest?
A week ago Chris Rolinson, associate professor of photography and photojournalism at Point Park University, set up a time-lapse camera to take snapshots of the nest. Many hours later he retrieved the camera hoping for lots of peregrine activity, but they did not oblige. On the other hand, he captured a really clear shot of one of the parents, a chick, and a prey item at the ledge edge. Click on the image above for a larger view.
The falconcam also takes snapshots but it sways in the wind so most of its images are blurs of the facade. Yesterday there were three tantalizing photos.
Here a chick traveled closer to the nest opening. He looks pretty big.
And around one o’clock they lined up so we could count heads. In the marked up snapshot below there are three peregrine chicks facing us.
A few minutes earlier there may have been a fourth with his side to the camera and his face hidden by the wall. His nearest sibling appears to be looking at him. (Notice that his location is dark-colored in the image above.)
So how many chicks do Dori and Louie have? Certainly three, perhaps four.
Watch the Downtown Pittsburgh falconcam and tell me what you think.
p.s. We’re looking forward to more from Chris Rolinson when the chicks are more active.
(photo at top by Christopher Rolinson. Time-stamped photos are from the National Aviary falconcam at Point Park University)