24 March 2024

Incubation began last week at the Pitt peregrine nest. Carla and Ecco are now 6 or 7 days into The Big Sit.

To incubate their eggs and brood their chicks, birds open their warm feather coats by developing a brood patch for the breeding season. The brood patch is bare skin on their bellies that they place directly against the eggs to keep them warm. It has no feathers or down and lots of blood vessels close to the surface. When the bird is standing upright, surrounding feathers fall over the patch to cover it. If you had the bird in hand, as this bander holds a kestrel, blowing on the bird’s belly will move the surrounding feathers away so you can see the brood patch.

Both male and female peregrines have brood patches and both incubate the eggs. Instead of one big patch as on the kestrel, Birds of the World describes peregrines as: “Both sexes have paired lateral brood patches. Less well developed in male.”

To expose the brood patch and incubate the eggs, peregrines move the surrounding feathers out of the way by bobbing up-and-down and side-to-side. In this video Carla turns the eggs with her feet, then bobs to open her brood patch before she settles on the eggs.

Female peregrines incubate all night (with this interesting exception) but the amount of time the male incubates during the day depends on the couple’s preferences.

Some males love incubation duty, others not so much. Birds of the World sites several studies (paraphrased): “Based on studies in interior Alaska, males incubated about 33% of time. A study by Nelson suggested that for the Pacific Northwest male, incubation was 30–50% of the time. An extreme case in New Mexico was a male incubating as much as 87% of daylight period.”

Ecco loves to incubate so Carla and Ecco are still working it out. In this 20 March video Carla wails off camera “I want something to change!” Yup. She wants to incubate. Ecco eventually gets the message.

Peregrine eggs hatch 33-35 days after incubation begins but when did it start at the Cathedral of Learning?

Typically incubation starts after the next-to-last egg is laid — that would be Egg #3 on 19 March at 2am — but it looks like it may have begun on the 18th before that egg was laid.

Two Day-in-a-Minute videos illustrate the difference between incubating and not. This one on 17 March shows that the two eggs are often exposed.

On 19 March there are 3 eggs and incubation has definitely begun. Notice that Ecco is on the nest more than half the time on that day –> 54%. He’s the smaller bird and is present 390 minutes out of 720 mins in the video. No wonder Carla wailed at him on the 20th!

So incubation began on either the 18th or 19th of March. It is hard to tell about the 18th because it was cold that day (28°F to 36°F) and Carla and Ecco may have covered the eggs to protect them from freezing without opening their brood patches(*).

We’ll never know for sure whether the brood patch was open because we can’t see under the bird.

Carla and Ecco have 27 to 30 days to go for The Big Sit at Pitt. Watch them on the National Aviary Falconcam at Univ of Pittsburgh.

(photos and videos from the National Aviary Falconcam at Univ of Pittsburgh)

(*) EXPLAINING DELAYED INCUBATION: Some species, such as bald eagles, incubate immediately as soon as an egg is laid. Within these clutches the chicks hatch days apart from each other. Others species, such as peregrine falcons and ducks, want the clutch to hatch all at once so they delay incubation until the clutch is (nearly) complete. During freezing weather the eggs must be protected from freezing. Covering them without opening the brood patch is one way to regulate the start of incubation.

21 March 2024

Carla laid her fourth egg at the Cathedral of Learning at 10:25a this morning, 56.4 hours after Egg#3. Most of us didn’t realize it happened. Thanks to Laurie Kotchey’s sharp eyes and her comment on my blog, I knew to start looking for Egg#4 when I got home at 11:30a.

The video below shows the egg-laying moment, sped up to double-time, but you won’t see the egg itself because Carla is facing the camera. Instead, watch her behavior. She eventually stands tall, opens her beak and points it upward. Wait for the moment when she bows down and raises her tail as she lays the egg.

I believe this is Carla’s last egg for the year because she has already started incubation. More about incubation in an upcoming article.

Watch the Pitt peregrines on the National Aviary Falconcam at Univ of Pittsburgh.

(photo and video from the National Aviary Falconcam at Univ of Pittsburgh)

20 March 2024

Back in early February, Malcolm Kurtz stopped by East Liberty Presbyterian Church to photograph the resident peregrines. He found them carrying prey, perching on the steeple and hanging out together.

Malcolm first noticed the birds in December when “[he] saw an adult perched on the steeple from an overlook on Chatham’s main campus.” Good thing he followed up on it. The red aircraft hazard lights, which don’t look red from a distance, had fooled me so often that I stopped looking for raptors on the steeple. Malcolm’s photos show that a perched peregrine is about the same size as the lights but the bird is hard to see. If you’re near the steeple look carefully. How do peregrines manage to match every building they perch on?

While on site on 8 February Malcolm saw the female (at right) bring prey back to the church and eat it while the male looked on (at left). Notice that she is peachy compared to him.

Meanwhile Adam Knoerzer checks on the peregrines every day and has noticed they’ve changed their area of focus. On 14 March he recorded the male flying in with prey and, later, the pair flying together.

The peregrines have been spending a lot more time on the east face of the steeple.

This is the side of the steeple facing Highland Avenue. Around a month ago, I primarily spotted them on the opposite side of the steeple and south face, but they have tended to perch over on this face in the past week or two.

— email from Adam Knoerzer, 14 March 2024

• Green = floodlight where female likes to perch.
• Red = plucking perch where male prepares food for female.
• Blue = possible peregrine nest zone. Shows sticks leftover from old red-tailed hawk nest. Female often perches here at sundown. In first video below, male drops off food at this location.

Their change of venue probably reflects the lack of substrate anywhere else on the structure. This location is probably the only place that has an obstruction to prevent their eggs from rolling off the building.

If you want to see the East Liberty Presbyterian peregrines look from the Highland Avenue side first.

(credits are in the captions)

19 March 2024

This morning Carla laid her third egg of the 2024 season at 2:01am. Because her nest is visible on a timestamped camera, I can tell you she laid the 3rd egg 52.87 hours after Egg#2. (Egg#2 was 53.14 hours after Egg#1.)

Here’s a video of the egg-laying moment, sped up to double-time, which happens to make it obvious.

By 6:29am Carla had been off the eggs for 90 minutes (standing up). That’s a very long time to be off the eggs if she had already started incubation because they would cool dangerously in this morning’s freezing weather.

Peregrine incubation begins when the female has laid her next-to-last egg but it is always hard to tell when it truly starts if the weather is cold because the adults cover the eggs to keep them from freezing. When incubation truly begins, the parent exposes the brood patch and lays its bare skin against the eggs. Peregrines can vary how much skin is exposed thus delaying the actual start of incubation until the clutch is nearly complete.

Learn more about the parents’ roles in incubation here. By the way, the bird covering the eggs on recent mornings has been Ecco.

Watch the Pitt peregrines on the National Aviary Falconcam at Univ of Pittsburgh.

p.s. Happy Spring Equinox tonight: 19 March 2024 at 11:06pm.

(photos and video from the National Aviary Falconcam at Univ of Pittsburgh)