Saturday, June 17, 2006

Second fledge at Cathedral

Photo by Donna Browne --one day before fledging

From Donna's website this morning --

Saturday, June 17, 2006

FLASH! Youngest Fledges!

This morning at 10:20 am, Divine the Youngest fledged into the trees East of the nest and was bombarded by cat birds. Mom came with half a squirrel. More to come later...

PS Bruce Yolton called a few hours ago to tell me the news. There will be more on his website too, if he can manage to tear himself away from Morningside Heights.
Here's a link for Bruce:

Blakeman on the retrieved eggs

First to answer a question many readers have written in to ask: what did I mean when I wrote that when the eggs were examined they showed "no evidence of embryonic material "? The answer, quite simply, is that there was no sign within any of the eggs of a hawk chick developing, none whatsoever.

Now, here are some thoughts about this finding by John Blakeman, These are followed by a question I sent JB today, and his answer.

There can be only three explanations for the lack of any embryonic development in the eggs. They are:

1. Infertility.
2. Chemical Toxicity.
3. Egg Cooling.

Infertility. Would it be possible that Pale Male is now too old and no longer has viable sperm? Could be. We don't have any data that I know of concerning reduced spermatogenesis in older red-tails. The bird shows absolutely no other geriatric complication, and he copulated frequently and normally this year. I doubt that this is the cause. If he wasn't producing copious volumes of sperm, I doubt that he would have copulated so normally.

Chemical Toxicity. Lab results are awaiting. But I doubt this is the explanation, either. Any chemical toxicant powerful enough to kill the egg or embryo almost surely would have also zapped the adults, or at least appeared in their behaviors, which were quite normal. I'm betting that pesticides or pollutants won't be discovered in the eggs. On the other hand, we need to account likewise for the failure of the Trump Parc eggs this year, and perhaps some infrequent or uncommon poison got both of these clutches. The lab chemistry should affirm or deny this cause.

Egg Cooling. Lastly, if the eggs were cooled for any length of time in the first few days in the nest (after incubation begin in earnest), the microscopic zygotes would have died. Without other evidence, I'm leaning strongly for cooling to be the explanation. Yes, Lola sat diligently and normally, so prolonged cooling wasn't her fault. But if the eggs were in direct contact with the metal pigeon prongs in the cold of March, sufficient heat could have been conducted away from the eggs by these heat sinks. The metal prongs are attached to the metal nest cradle beneath the nest lining material. In the cold weather of late March, a few degrees of heat could have been continuously conducted down through the spikes and out of the eggs, no matter how tight the nest lining was.

But how might this have been different from the many previously successful nestings of Pale Male and his mates on earlier nests, all of which had pigeons spikes?

One explanation would be that for whatever reason, those developed nests were thicker, elevating the eggs entirely above the spikes, with the eggs shielded from the metal by sufficient sticks and nest lining material. Did the new nest cradle structure cause the birds to construct a more shallow nest, through which the spikes protruded? I believe that must be considered, especially if egg chemistry shows no toxins.

I hope that detailed telephoto pictures of the nest were taken when the eggs were retrieved. These might reveal any involvement of the pigeon spikes, particularly if they could be seen directly below or adjacent to the eggs. It will be recalled that one of my other prognostications was that the eggs might have been lethally pierced by the prongs toward the end of incubation, when egg shells are known to thin from the carbonic acid produced by the respiring bird in the egg. Of course, the retrieved eggs show that no such piercing occurred. The eggs also reveal that there were never any developing, respiring birds in the eggs, so the normal egg shell thinning couldn't have happened.

For those who might think me to be casting about in random directions for an explanation, perhaps I am. But that's how field biology must be done, awaiting final evidence and data. The lack of an on-site digital camera that would reveal all nest dimensions, structures, and activities mandates such informed speculations. At best, I can be only one third "correct." I could be wrong altogether, when some other, unknown lethal factor is discovered. But I hope all of this prompts others to examine the evidence and come up with their own explanations. We await a full report of both the lab findings and whatever detailed visual inspection of nest was conducted.

--John Blakeman

Postscript: My question to Blakeman and his answer:

John, a few months ago you wrote
"When Pale Male begins to age out, I think other things will first become evident. He's likely to be less active in hormone-driven nesting behaviors in January and February. He's likely to spend most of his reduced energies merely hunting, not in breaking off twigs and carrying them to the nest. He's less likely to ascend and engage in courtship dives"

Could you steer me to any literature on this idea-- ie that there is some connection between a bird's observed behavior and fertility?

Blakeman replied:
There is no literature on this. There is virtually no cogent articles on any of the attendant matters. No one any where has studied a persistent red-tail nest or pair. All of the studies are population ones, not of continued single nests or single pairs. In these studies, no one can possible know the age of full adults. Once again, this is why the Pale Male nest is so important. The exact age of the tiercel is known. His previous breeding successes are known. We know what he eats. We know (sort of) what he captures and feeds his mate and eyasses. More is known about Pale Male than any other single wild adult red-tail.
But I'm (as so often) I'm still speculating, based upon my personal experiences with single red-tails over many years, one bird I had for 13 years, and another for 16. I've known falconers who've had even older red-tails. There is one falconry account of a red-tail that lived, poorly, into its twenties. But the poor thing had arthritis, couldn't fly, and had trouble picking apart its food. It should have been put down. Instead, heroic measures were extended just to keep it alive after it lost all of its normal functions.
It's from these experiences that I proposed that if Pale Male was becoming impotent other behavioral anomalies would be seen. And none this year were seen. The fact that he copulated as frequently as before suggests to me that his hormones were still at normal levels. Copulation is driven by the same sex hormones that cause spermatogenesis, suggesting that if a hawk is copulating it also has viable sperm. The sperm are produced by the same hormones that prompt the copulation. The two reproductive elements are hormonally linked.


Friday, June 16, 2006

Pale Male & Lola's eggs: News

Red-tailed Hawk eggs
A preliminary report has come in from Ward Stone, the wildlife pathologist who was given the three retrieved eggs from the 927 Fifth Avenue nest last Tuesday. He found no evidence of embryonic material in any of the three eggs [which were intact when he received them.]

I received this information from a reliable source, but I haven't spoken to Ward directly. I'll try to do that to understand what conclusions may and may not be drawn from this finding. I'll also be getting in touch with a few other experts to try to find out what this might mean.

Meanwhile, the eggs will also be analyzed for a variety of pesticides, rodenticides, herbicides etc. The results of the toxicology series might be more illuminating.


Here's a picture, taken by Chris Lyons, of the white-chested Fordham fledgling. We started out thinking that the orange color on redtail nestlings' chests was something unusual. Now we're coming to realize that in reality the white chest is the rare one. We can't find any other white-chested immature redtail besides the one Fordham kid. [NB the other two Fordham chicks were orange-breasted.]

PS Still one to go at the Cathedral

Thursday, June 15, 2006

Not yet!


As of 7:30 this morning [Thursday, 9/15/06] one kid still in the nest at the Cathedral of St. John the Divine.

Click on the link above for latest picture by Ardith Bondi. I couldn't upload any images onto this page this morning. I was also warned that the parent site of this page [] will be out of service later this morning. Don't know when they'll be back. . .I hope by tomorrow.

Second Cathedral kid hangs back

One nestling to go -- 6/14/06
Photo by Ardith Bondi

Ardith Bondi usually joins the Early Birders on Wednesdays. She wasn't there yesterday morning. Here's why.

Hi Marie-

Sorry I missed your walk this morning, but I couldn't resist using the
morning light for photography at St. John the Divine.

I wonder if the second eyass finally got the courage to take the plunge. He was still up there at 1:30 when I left. He would go onto St. Andrews' head looking like he really wanted to go, flap a bit and then take a nose dive into the back of the nest (pretty funny). What a wuss... And he can afford to be because he keeps getting food deliveries.

See you soon,


Wednesday, June 14, 2006

Pale Male's a school mascot

Pale Male last March
Photo by Lincoln Karim

Just received the following e-mail, addressed to me and Lincoln:

Dear Marie and Lincoln,

After much planning and hard work, Nina Gunther-Segal has finally been successful in her bid to name Pale Male as the official PS6 School Mascot. She asked me to invite you both to the official ceremony, to take place on the steps of PS6 ...
Note: PS 6 is an excellent public elementary school on New York's upper East Side, located not far from Central Park and Pale Male & Lola's nest. [MW]

Principal Dan Feigelson, School Librarian Kim Bader and Nina have worked together on the project and will unveil a plaque which will be permanently affixed to the facade of the school building. Inspired by Lincoln's photography, the plaque depicts Pale Male with accompanying text by Nina -- a lasting testament to the importance and vitality of the Central Park "classroom".

Cathedral news

Photo by Bruce Yolton
First Cathedral fledgling resting on angel before [possibly] visiting sibling still on nest -- 6:30 pm, Monday 6/12/06

Second fledgling may have taken off by now.

The parents will continue to feed and educate these young hawks for at least three more weeks.

Tuesday, June 13, 2006

Pale Male and Lola's eggs retrieved

Photo in 2005 by Lincoln Karim
Many readers have been asking about what happened to the plan to retrieve the eggs from Pale Male and Lola's failed nest. Here's the story as I witnessed it this morning, and based on further information I received later:

At about 8:45 this morning Chris Nadareski of the DEC leaned over the roof of 927 Fifth Ave with a small net at the end of a very long wooden handle. He manipulated the instrument into the redtail nest and one by one successfully scooped up three intact eggs. They were to be taken this very day to Ward Stone, well known wildlife pathologist for the DEC whose lab is near Albany, New York. I was told that he would have a report on the eggs within a few days. I do know that some of the toxicology tests take a while, so I wouldn't hold my breath for news.

I'll post the results as soon as I know.

Squirrels as redtail prey

Central Park squirrel looking up at a red-tailed hawk
Photo by Cal Vornberger

Lika Levi of Scarsdale writes:


Reading about squirrels being a tough prey reminded me of a scene I witnessed a while ago in our backyard.

There are quite a few oak trees around here and quite a family of squirrels running around. One day, I now think I saw a RTH with a squirrel in its talons. These squirrels around here are mighty feisty... A couple of minutes later the RTH had to release and let the squirrel go... I could not believe my eyes, but I now understand the squirrel must have bitten the RTH... I have not seen this episode repeat itself yet here... but I think I have seen a RTH go after smaller prey around here.

Thanks for your interesting post.

Monday, June 12, 2006

Lyons answers Blakeman and They're in Kansas too

A red-tail fledgling in Kansas
Photo by Pat Floersch
[see her note after Chris Lyons' answer to John Blakeman, below]

From Chris Lyons:
Briefly responding to John Blakeman's response [see post directly below]--I agree the purpose of the orangey chest color isn't to make the chicks more visible--if anything, the pale-chested chick should be more visible. My theory, imperfect though it be, was that it makes them more ATTRACTIVE--just a little. That seeing and/or hearing all the chicks, who are often in different locations, and in any event are competing for the same food, the adults might be a little more inclined to feed an orangey-chested one, because the color stimulates their feeding response. I've seen no direct evidence of this on the nest, however.

One would have to spend a lot of time carefully documenting the feeding behavior of a lot of Red-Tail families with both types of eyasses to know if there was any substance at all to my speculation. The pale-chested chick on the Fordham nest has been very insistent about getting his share, and has shown a great deal of energy overall. Even if I'm right, a pale-chested chick probably wouldn't starve if there was plenty of food to go around. But getting a little more food in the weeks following fledging could make a difference with regards to who survives to full adulthood, and gets to breed.

As to the red tail, there are clearly many factors that go into successfully attracting a mate; hunting prowess, experience, overall vigor, ownership of a good territory, and a sense of humor never hurts. Kidding. I think. ;).

From Pat Floersch:
Hello Marie,

This is one of three baby red-tails living in an oak tree behind our house in Overland Park, Kansas. This is a suburb of Kansas City. All three eyasses have orangy chests as have the previous year's eyasses.

Having only seen this kind, I have been fascinated by the discussion on your website and the white chested one was really interesting with his orange chested brethren.

Sincerely, Pat Floersch

Blakeman shoots down theory and proposes new one

Cathedral Dad on Angel Gabriel
Photo by Cal Vornberger

Chris Lyon's conjectures on the recent appearance and helpfully-attractive function of the orange-breasted red-tail eyasses are interesting. This is good biological thinking, the start of all good scientific explanations. I'm glad he put forth his thoughts, prompting others to offer theirs.

And of course, here are mine.

First, I have to agree with Chris in thinking that this trait is more common (at least in the East) than I first thought. I've never seen one of these out here in Ohio, but a good falconer friend says that he has seen one this year on a local nest.

The trait is now obviously genetic, not diet-produced. And where present, it may be a dominant trait.

Chris's suggestion that this brighter breast plumage might attract adults to fly over and feed the new fledglings is reasonable. But my experience is that parents have very little difficulty finding newly-fledged eyasses to feed. When young red-tails leave the nest, they are almost always hungry. Therefore, they are prompted to fly after food-providing adults whenever and wherever they are seen.

At the start, before eyass flying skills are well developed, the young birds do have a tendency to sit on branches and vocalize for food. Because they can't fly (or land) very well, these inexperienced birds often get parked in among leafy branches where, indeed, they can be hard to find. A brighter breast would help disclose their location, for sure.

But so would the typical white breast, against the leafy green of the arboreal vegetation. Parents really have no difficulty in finding their young because when hungry, the new yearlings make a lot of noise. It's really the other way around. The question is not how do parents find their wondering offspring. It's how do the young hawks find their parents. The eyasses make a racket to attract their food-carrying parents, and they also flap their wings or fly after them.

By late June, the yearlings are fully on the wing and they tend to chase after the parents wherever they go. When parents retrieve food for the yearlings, they must be careful not to be physically attacked by their offspring. Consequently, parents usually try to remain distant from the young hawks, dropping food away from them.. The yearlings who follow their parents to hunting perches distract the hunting efforts and successes of the parents, so adults often try to fly off without their kids in tow or pursuit. For the first half of the summer, the hawk fledglings simply complicate the parental duties of the adults.

Sooner or later (usually later), the yearlings will begin to hunt on their own. But that's usually after Mom and Pop begin to discontinue daily food provisions. The adults appear to finally get so pestered by the begging calls and thieving pursuit flights of their young that they just fly off and stop feeding them altogether. Often, they turn the tide and fly at the young, driving them to the periphery of the territory. Reluctantly, the yearlings begin to understand that they will have to find and capture their own food. The cutting of raptor apron strings is not an elegant process. It is often downright uncivil, even moderately violent.

So in summary, I don't believe there is any real selective advantage with the orange breasts in allowing more successful feeding of new fledglings. Yearlings could be virtually invisible to their parents, but would still be found as the young fly eagerly to the discovered parents. It's not how do the adults find their young. It's how do the young find their food-providing parents.
This raises another plumage-related question never asked here, I believe. What function does the red-tail's red tail serve? It would be reasonable to presume that it allows identification of adults. First year birds don't have a red tail. All adults do. Therefore, it keeps the immatures out of the mating (pair bonding, not copulation) process.

But there are two complications with this explanation. First, there have been a number of cases where immature red-tails have pair bonded with adults at nests. I'm not certain if these have always produced eyasses, if immatures are capable of inseminating females or producing eggs. Nonetheless, it's clear that the red tail is not an absolute requirement for pair bonding to occur.
Secondly, I studied a pair of Ohio red-tails that produced a single, normal eyass. The father was a quite typical male. But the mother was an almost purely white "leukistic" or albino, without a red-tail. She had a few minor streaks of red in her tail, but in color she didn't look like a red-tailed hawk to anyone, hawk or human. Obviously, this pair formed and produced an eyass without any behavioral prompting of the red tail.

There are a number of buteo hawks (red-tails are in the genus Buteo) with red tails in the world. There is a species in South America that is very, very similar to the North American bird that we know and love so well. In Africa, there are at least two red-tailed buteo species. Why, then, the red tails? Who knows.

But they sure are beautiful, aren't they? Just how exciting would Pale Male be if his tail were a mere brown? Do red-tail females have an elevated sense of beauty and therefore tend to mate (and yes, copulate) with only the most elegant, best-colored males? Is the red tail just a raptorial form of high fashion and aesthetics? Are the aesthetic skills of female red-tails the ultimate source of our delight with the plumage of these fine birds?

--John Blakeman

Sunday, June 11, 2006

Divine news!

Proud Dad in Morningside Park, day before 1st fledge
Photo by Bruce Yolton

I spent the weekend in a country cabin with no telephone and no internet access [but lots of birds and moths]. Two phone messages waiting for me on my return , one from Bruce Yolton and one from Jimmy Lewis, filled me in on the exciting news: one of the Cathedral nestlings fledged today, at 2:20 pm. Another piece of news, in a message from Noreen, was about the Fordham hawklets. Though all three have fledged, when she went up to the campus today she found all three were back in the nest. Who said You can't go home again?