Wednesday, May 18, 2011

Drama in the sky above the Franklin Institute

One of the Hawkwatch blog readers (Erik) shared a comment about the excitement he witnessed with our haggards high in the sky above the Franklin Institute last week:

"I was across the street from the nest today (Mother's Day) observing with my father. We spotted the formel on top of the green circle on the far building across from the nest - the building with weird 80's designs on it. She took off and we lost her. 

Then we saw the tiercel with the formel and at least three other red-tails - a juvenile and some adults - which all began to kettle up above the corner of the Franklin Institute above the nest. We both thought this was interesting behavior as we had never seen such a kettle in an urban environment. 

Then the formel gave a loud "kee-awww." That's when we spotted the peregrine falcon way up above. It folded up and dove right on the tiercel who grappled talons for a brief moment. This happened three more times before the peregrine got bored and flew off. The other red-tails left as well and the pair hunted down two rats which they began feeding to the trio of eyasses who were completely unaware of the drama which had unfolded above them. What a day! 

My father and I used to band raptors for fish and wildlife down at Kiptopeeke in Delaware. Are the Franklin birds banded? We couldn't see from the parking area. As for the other red-tails there was a juvenile (maybe second year?) and two other mature birds. The peregrine/red-tail dog fight took place a couple hundred feet up so it was tough to get a solid look at the falcon."

I shared this report with John Blakeman, and as always, he generously shared his knowledge in explaining what was happening:

"The stooping (diving) behavior of the Peregrine is quite normal. There is obviously a Peregrine aerie [nest] within a few miles of the Institute Red-tail nest. Peregrines try to warn any intruding raptor by diving at it, as in this case.
But the Red-tail was in no real danger. The Red-tail sees any falcon flying above, and although it can't fly as fast as the falcon, it can instantly turn over in the air and offer six sharp, long talons as the smaller falcon approaches. The hawk will not be physically attacked by the falcon unless it gets close to the falcon's nest.
But a Peregrine will attack and kill big raptors. When Peregrines began re-nesting on bluffs along the upper Mississippi River in recent years, Great-horned Owls commonly preyed upon the falcon eyasses. At the start, the owls had no fear of the much smaller falcons, and the falcons had no experience with the giant, predatory owls.
But that has changed. The falcons eventually learned to attack the owls whenever seen. The big owl is even less maneuverable than a Red-tail, and the falcons learned to kill these birds whenever seen anywhere near a falcon aerie. The owls weren't dumb. They've learned that it's no longer wise to try to fly anywhere near a falcon aerie. Now, Peregrine eyasses successfully fledge from Midwestern falcon nests. The falcons have learned to attack the owls, and the owls have learned to stay clear of falcon territories.
That's the scenario with the Peregrine stooping at the Franklin Institute Red-tail. It's to keep the hawk away from the falcon nest, which it will avoid. The hawk and falcon will have some aerial encounters, but both will be safe. For the Peregrine, the stoops are impressive shots across the bow, to keep the hawk at distance.
The presence of the other Red-tails, perhaps some immatures (with their brown tails), is a bit more problematic. Are these last year's fledged Franklin Institute eyasses? No way to know. They might be; or they could be some straggling migrants heading slowly back north.
This is exactly why urban Red-tail eyasses need to be banded, preferably with colored bands, so their geographical fate can be determined. Up in Manhattan, there is the (unfounded) presumption that most or all of the urban Red-tails nesting there are direct progeny of the famous tiercel patriarch Pale Male. We still don't know if new urban Red-tail nests and territories are occupied by a continuing stream of migrants from adjacent rural areas, or by hawks hatched in the urban areas themselves.
Obviously, at the start, there was an incursion of rural Red-tails into urban areas. Pale Male was one of the first of these, of course.
But today, where do the nesting urban Red-tails come from, from other urban Red-tail nests, or do most of the new nesters come in from the countryside? Without band and detailed plumage identification (exceptionally difficult), this will be a continuing biological mystery."

--John Blakeman


  1. Wow! Such a soap opera! Another chapter for your eyeass diaries!

  2. This is actually good news, to me. It's the first I've heard of peregrines nesting in Philly in several years. We used to have a pair that lived on the City Hall tower in the 1990s. When renovations began, it disturbed the birds and they moved to the Bell Atlantic (now Verizon) tower. There was even a closed-circuit camera on the nest that could be viewed in the lobby. (This was in the days before streaming video on the internet was available.)

    But the last I heard of those birds was in 2001. They didn't return to that nest site after that summer, and from then until now I hadn't heard of any Peregrines being in the city. I'm glad they're around. Though I hope that they and our red-tailed hawk family give another a wide berth!

  3. This is the 2nd year in a row with Peregrines nesting in Philly. This year they are on City Hall. I think they were on a different building the year before. In fact there was just an article posted on

  4. Wow, can't believe I read this post this morning and got to see the same thing later in the day. I work at the Hopsital of the Universityof Penn and we've had a pair of nesting hawks here for years. I'm not sure how many but at least 5-6. I've often wondered if the Franklin Institute redtails are descendents of our birds. They love to perch on the top of one of the buildings right across from my office. Its called the Irvine Auditorium and has a tall spire with many perch-worthy extensions.They also sometimes chill out on the weather vane. My first sign of spring each year happens in February when the pair start "getting busy." Anyway, today I looked out the window and saw a falcone dive bombing one of our haggards ! What a coincidence or is this the same falcone trying to be tough with all the city hawks ?

  5. Every time I think I couldn't be more happy being a Philly resident, something like this story just adds to it. This is absolutely amazing! I saw a wildlife program on a PBS channel showing a male Peregrine launching himself from a cliff nest with eyasses in it, to "warn" a Red-tail that got too close in the same way that you described, Erik, but without the back-up forces that our Red-Tail haggards had. Thank you for sharing your story.

  6. so wonderful we can share what we see in the sky and view the closer result on cam...then have those in the know explain this behavior to us.
    Thank You So much for all the effort.....

  7. Years ago, I used to work across the street from HUP, and I remember seeing those red-tails on a regular basis. I'm glad to hear they're still there.

    I also noticed that the songbirds in the vicinity of HUP *did not like* when medical helicopters came zooming in to land on the roof of HUP or CHOP. I guess they always had one eye on the sky above because of the legit danger of predation from hawks, so they reacted with alarm when a big helicopter suddenly appeared overhead.