Saturday, April 16, 2005

The suspense is killing us!

Well, today was the due date. [Actually I thought it was yesterday.] But since we can't see into the nest, we can't be sure when incubation of eggs really began. By most calculations, today would be day 32 of a 28-32 day incubation period. The chicks should hatch today. But, some people say the incubation period is 28-34 days. And maybe PM & Lola hadn't started sitting on eggs when we thought they had. In any event, the suspense is almost palpable. High anticipation and anxiety reigns around here.

I'm off to the hawk bench now. Maybe something will have happened while I'm in the subway. Or maybe nothing...

R.I.P. Dash---from your friends in Central Park

Photo taken on 3/27/05 -- Dash is the male, above.
Lily continues to sit on eggs.

Here's a link to the webcam:

Very Sad News about the California Kestrels


Thought you might want to know...this evening at about 6:45, we saw a hawk (later determined to be a Sharp-shinned) on top of the nestbox for our kestrels. The male kestrel was inside, having just made a "change of shift" with the female. The male then left the nestbox, and within a second or two, the Sharp-shinned had snatched him by the tail, taking him to ground. The female kestrel was returning to the nestbox, and she became extremely agitated, dive-bombing the site (just out of our sight) where the hawk had taken the kestrel down, calling out and swooping down repeatedly. She made several flights between the nestbox and one of their hunting perches, each time making dive-bombs on the (unseen to us) Sharp-shinned. Of course, it was all to no avail. We waited about one-half hour, and then went to confirm the kill (we try very hard to employ a non-intervention philosophy...the sharpie has a family to feed as well). The Sharp-shinned was still on the ground, feeding on the last of the carcass, and she flew off as we approached, leaving only kestrel feathers on the ground.

We do not know at this time what the female kestrel will do. She is on the eggs tonight, but given that she still has approximately 2 weeks of incubation to go, she may well abandon the nest. If so, it's very possible that she will try to locate a new male with which to breed. Or, she could stay on the eggs and try to incubate and raise the chicks herself. Perhaps John B. would have some insight here?

In any event, although this was quite sad to witness, we do take comfort in that it was a natural event...we would have been considerably more distressed if either a) the male disappeared and we never found out why, or b) his death was caused by humans (shooting, collision with a car, poison, etc.).

For now, though, we're just waiting to see what will I said, we try to take a "hands-off" approach to wildlife (although it may be argued that by putting up a nestbox, we have already violate that ethic). We will definitely miss Dash...we're just hoping that Lilly survives by being smart enough to know that Sharp-shinneds are around. (BTW, if she abandons the nest, we will lower it and clean it out, and then re-erect it with pigeon spikes on top to prevent future ambush attacks like this).

Anyway, our thanks to all of those who have been following our kestrels from your website. Kestrelcam is still up and running, and we'll all just have to wait and see what Lilly has in mind. Who knows? Maybe she'll be able to continue on her own?


Blakeman: I'll answer questions soon

More really fine queries. But I'm catching up on lots of paperwork. . . I'll try to have responses in a day or two. The observations on hawk wing aerodynamics are important and interesting.
I drove past a local red-tail nest today on returning from a prairie design workshop, but didn't have time to even stop. Nonetheless, a parent was standing on the rim of the nest leaning over it. I'm certain that it was feeding a newly hatched eyass or two. Good stuff.
And I know everyone will become ecstatic when the 927 eggs hatch. These good questions may have to wait until things settle down, should an eyass appear this weekend. I'll try to get something in as soon as I can.
And I want to counter your rejoinder. But later.

John A. Blakeman

Friday, April 15, 2005

Notes from the Hawkbench and possibly the last report about the Screech-owls

Field Notes 4-14-2005

Sunset 7:35PM,
Temp. 50F,
Wind Chill 46F,
Wind E 12MPH,
Gusts 16-19MPH,
Humidity 78%
Mostly sunny and cold,
Prey Tally- pigeon,

Trump Parc Nest: Lincoln's friend with a view of the
site reports two eggs have rolled out of the nest.
4:35PM Arrival, Jr's nest looks much as it did
yesterday, no hawk in sight.
4:55PM Jr. with twig makes several passes in front of
nest. Jr. lands on the nest, stands looking at
4:56PM Mrs. takes off from S end of nest and down. Jr.
continues to survey territory.
5:00PM Jr. disappears into concave of nest, reappears
with head near wall, digs, pulls twigs with beak from
edge of nest toward center. (Jr. has the brow similar
to Pale Male that makes him look concerned all the
5:04PM Jr. disappears into nest.
5:23PM Hawk (Mrs.?) appears carrying twig and circles
construction on adjacent to nest roof three times.
More circling over Cottage Roof, third building from
Trump to he W.
5:25PM Tourists from Dallas ask about Hawks.
5:26PM No hawks seen in nest or in sky.
5:35PM Exit

The Hawk Bench Approx. 6:10PM
Hawkwatchers included among others, Katherine,
Elizabeth, Katherine, Ric, Clare. They reported with
some agitation that a bit earlier Pale Male had
brought a large pigeon for Lola's dinner and had
landed with it on the railing of the S false terrace
of Woody. A woman in that apartment had come to the
window and given it a great bang. Pale Male startled
and flew with the prey over to Linda. Where he stayed
for some minutes. He then took the prey to Lola on
the nest and according to Clare, Lola flew to a
bulding on 79th to eat, almost dropping the prey off
the perch but grabbing it back just in time. In the
meantime, Pale Male had left the nest (?) and it was
unattended for approx. 20 minutes at which time he

102nd St. Screech Owl Family

Owl hunters: Marie, Lee, Noreen, and Donna.
The Screech Owls were not in the oak where they had
roosted yesterday. Though all known roosts were
searched as was the Ravine, the Owls were not found.

Submitted: Donna Browne

Blakeman: "I've retreated from my former answer" re whether other hawks in CP are progeny

Below, Blakeman's new thoughts on the progeny question. At the end I add a small rejoinder of my own, just to keep the conversation going.

You know that I went on at length back in December about how all the other red-tails in the Central Park area weren't likely to be Pale Male progeny. I expounded on how the adults will drive off the young to protect the larger adult hunting territory. Secondly, I noted that an incursion of Pale Male kids would promote mating of close kindred hawks, resulting in genetic problems.
But from your many descriptions of pale colored birds, and other cogent observations you and others have made, I've retreated from my former answer of rather standard field biology, that the kids shouldn't be there. It looks like they are, for whatever reason(s) and in whatever densities.
Now the question. Did the new NYC ledge-nesting red-tails select those sites because they were raised in and fledged from the 927 ledge nest? Or, might there be another explanation?
I really don't think the birds are nesting on ledges because they were hatched on ledges. As I mentioned before, little eyasses are rather stupid and involve their minute, developing brains with vocalizing, feedings, flapping wings, and defecating. Frankly, until an eyass can fly, it doesn't know at all what’s supporting the nest – nor does it care.
Why, then, the recent preponderance of ledge nests? I'm guessing that it involves the multitude of people under the trees that would be the conventional sites of red-tail nests. Even in the West, where big trees are available, trees are used over ledges. Red-tails prefer trees when they are available.
I've never elaborated upon the inordinate tolerance of humans, dogs, and who knows what other animal and mechanical disturbances the Central Park red-tails have endured. Out here in rural areas, a sitting red-tail is likely to abandon the nest and eggs when a single human walks within 100 or 200 yards of the nest. In Central Park, people are walking right near perching and nest trees. For overnight perching, the birds have learned to accommodate the multitude of strange bipeds (people) strutting hither and thither below.
But when it was time to build a nest, I think the presence of dogs and people might have been a bit over the edge. Trying to get a few sticks to lodge in the small crotch of a tree 40 ft up is no easy task. It requires full attention to the multiple construction tasks inherent in getting a secure nest erected. I'm guessing that the birds simply chose nest sites remote from any human experience, and those were way up on the sides of tall buildings. Up there, they could poke and probe and thrust and re-arrange sticks without any diversions.
One of the first anomalies of the 927 nest I noticed was not that it was on the side of a “cliff.” I've seen wild Western red-tails do that. But it was the inordinate height of the selected nest site. The western nests I recall observing were seldom much taller than tall trees, usually in the 75 to 100 ft range. Many were lower. I never recall seeing a red-tail nest either so high, or so close to the canyon rim (here, the roof line).
But no one can deny that both the 927 nest and the Trump-Parc nest are about as far from humans as physically possible. I think that’s the factor, the desired remoteness from humans and dogs.
This might also involve a perceived nest predation threat on the part of these two-legged ground animals. Who, among red-tails, knows if humans couldn't just shinny up a park tree with a nest in it and take a pair of eggs for breakfast? Perhaps the hawks are building high, remote nests on ledges because it’s the only place in Manhattan where a sitting hawk can be confident that a human won't disturb its calm incubation. As urbanized and acclimated to The City as these hawks are, they may still retain a requirement for a bit of private remoteness, some wild solitude and security. The high ledges are the only places that provide these.
But as always, merely thoughts off the top of my head (reflected, however, from watching both wild and captive red-tails for 35 years or so).

John A. Blakeman

John: You note that the little eyasses are too stupid to take note of their ledge origins, and therefore are not likely to be drawn to ledge nests when they're ready to breed themselves. But would this be a matter of intelligence? Might it not involve instinct.?Just like the principle of philopatry brings phoebes and orioles back to their former nest locations by instinct, not intelligence, might there not be some instinctive drive on the part of these eyasses raised on a ledge to replicate their early experience?

New edition of Red-Tails in Love

Note: I'd put this on my Home Page, but for the moment I can't easily make changes on it. So I'll post occasional non-nature news items here.

Just noticed that is now featuring the new edition of Red-Tails in Love on the book's home page. So for now that's the best place to order it from. Clicking on the book icon to the right or on the Home Page will get you B & N. Below is the link for the book's home page on Amazon.

Thursday, April 14, 2005

Prothonotary Warbler!!!

Jackpot! There have been reports from Prospect Park and Forest Park of appearances by that much desired early warbler, the Prothonary, but not Central Park. Today's the day. It appears in Jack Meyer's daily report along with other early migrants, as well as with the not-to-be-scorned bird Regulars.

DATE: Thursday, 14 April 2005
LOCATION: Central Park
OBSERVERS:Jim Hazel (Buffalo visitor), Audry Weintrob, Patty Pike, Kathy von
Hartz, Mary Birchard, Marty Sohmer, Jack Meyer

Double-crested Cormorant (Several, lake.)
Northern Shoveler (A few, lake.)
Bufflehead (2, Turtle Pond.)
Cooper's Hawk (Tupelo tree.)
Mourning Dove
Red-bellied Woodpecker (Ramble.)
Yellow-bellied Sapsucker (2, Ramble.)
Downy Woodpecker (Ramble.)
Northern Flicker (A few.)
Eastern Phoebe (Tupelo Field.)
Blue Jay
Tree Swallow (Turtle Pond.)
Northern Rough-winged Swallow (Several, Turtle Pond.)
Barn Swallow (2 or 3, Turtle Pond.)
Black-capped Chickadee (Ramble.)
Tufted Titmouse (Several.)
White-breasted Nuthatch (Ramble.)
Brown Creeper (Ramble.)
Golden-crowned Kinglet (Ramble.)
Ruby-crowned Kinglet (Several.)
American Robin
Yellow-rumped Warbler (Several, Turtle Pond.)
Pine Warbler (Several.)
Palm Warbler (Several.)
Prothonotary Warbler (Male, moving Point-Willow Rock-Riviera-Bow Bridge,
Louisiana Waterthrush (Lower Lobe.)
Chipping Sparrow (Ramble.)
Song Sparrow (Several.)
White-throated Sparrow (Several.)
Dark-eyed Junco (A few.)
Northern Cardinal
Red-winged Blackbird
Common Grackle
Brown-headed Cowbird (Point.)
American Goldfinch (Several.)

Pale Male delivers Lola's Dinner - 4/12/05


For John Blakeman: An old Question I'm asking again, in a slightly new way

Dear John:

Here's Donna's question:

Do red-tails build nests similar to the ones they were fledged from?

Your answer didn't really address the underlying reason we are asking that question and asking it so persistently. There are a number of red-tailed hawk pairs attempting to build nests on buildings all around the periphery of Central Park. But this species of hawk -- Buteo jamaicensis -- is believed to be a tree nester [by and large] not a ledge nester like the Peregrine Falcon or the Kestrel,

Wouldn't it make intuitive sense to wonder whether all these birds trying to nest on buildings were themselves raised on a building nest. In other words, our question is:

What is the likelihood that all these hawks are Pale Male's offspring?


Field Notes 4-13-2005

Sunset 7:33PM
Temp. 49F
Windy and cold
Mostly sunny
Prey Tally-2 pigeons

All of today's times are approximate as my pocket log
with great talent, fell from my pocket and dived
neatly into the park sewer at 102nd. Astoundingly good
aim, I must say. No dread loss as all previous notes
had been transferred to the computer.

Mr. and Mrs. Junior at the Trump Parc...

3:50-4:30PM I viewed Junior's nest on the Trump Parc.
It was hard to get an exact count from Hawk Rock, but
the nest looks to be about 30 stories up. There are
now evergreen boughs amongst the deciduous twigs. This
greenery was not there on my last visit. At 4:20, just
a sliver of the top of a hawk head could be seen above
the nest, it remained there until my exit at 4:30PM.

Pale Male and Lola at 927...

4:55PM Arrival- Lola on the nest and Pale Male on the
Oreo Antenna. Pale Male stayed a good half hour and
then disappeared. Lola turned eggs, preened, alertly
scrutinized the landscape, and on occasion while
standing outside the concave, would look down at the
eggs and as Kentuarian pointed out, seemed to be
listening to them. Lola also did a good bit of
preening while down in the concave today, particularly
on the edges of her wings. Near 6:00PM Pale Male
cruised in and perched on Linda 4, where there was
still bright sun. Lincoln reports that Pale Male did
eventually bring Lola her dinner.
6:06PM Exit

6:20PM The Owls at The Pool...

On my arrival, though a bit earlier than usual, I
found it strange that there were no people with
binoculars viewing the pines. The final straw for
realization to hit was when I got within hearing
distance and realized that the pines were full of
little chittery birds. No question, the owls had
changed their bedchambers. About that time Chris and
Fig [A faithful owlwatcher and her well-behaved border collie]
arrived and we decided to try a Screech Hunt in
the Ravine. And we found them, high up in an oak not
far off the path. Unfortunately I was unable to
remain for Flyout.
7:15 exit.

Submitted- Donna Browne

Project Safe Flight- A Call for Volunteers

Dear Website Readers: I've been involved with Project Safeflight since its inception. For those of you who live in NYC, volunteer if you can. I'll keep the rest of you posted about this worthy project as it proceeds.

Project Safe Flight scientific research program : May 7 through May 14

Volunteers needed

New York City Audubon's Project Safe Flight (PSF) is looking for volunteers to help with a scientific research program in early May. The goal is to better understand when and why migratory birds collide with windows in New York City.

Experts estimate that nationwide, a billion birds are killed each year by colliding with windows. Nearly 4,000 collision victims have been found in NYC alone since PSF began monitoring buildings in 1997. Forty-two percent of the species identified, including half of PSF's top ten most frequently found birds, are experiencing population declines. As the popularity of glass as a building material continues to grow, so does the collision problem - and the urgency of finding solutions.

The research program will gather data to determine what weather conditions, building structures and lighting are most adversely affecting our migratory birds. The research protocol involves monitoring specific downtown bird-killer buildings over a 24-hour period for eight days during peak migration. Volunteers will spend one or more hours between May 7 and 14 walking a specific route in the Battery Park area. Volunteers will attend an orientation session on Monday, May 2, where they will learn about the study methodologies and obtain necessary materials.

Study results will be written up for publication in a peer-reviewed journal. New York City Audubon is partnering on this research with the City University of New York, the Linnaean Society and leading ornithologists, including Dr. John Faaborg (University of Missouri), Dr. Sidney Gauthreaux (Clemson University) and Dr. Daniel Klem (Muhlenberg College).

For more information or to volunteer, contact Charles Hofer at, or call New York City Audubon office at 212-691-7483.

Project Safe Flight has been a leading force in educating the public about bird collisions at windows since it was founded in 1997 by NYC Audubon member Rebekah Creshkoff.

Wednesday, April 13, 2005

Blakeman answers Donna about Stick Size

Pale Male &Lola on Nest - 4/12/05
Photo by Lincoln Karim
[Check out that big fat stick!]

Let me summarize your good questions submitted to me about nest sticks (or twigs).
1. Why are only little sticks being used in NYC?
Frankly, I'm not sure it's so, although I first suggested this. It was only an hypothesis I related to a perceived (but errant) notion that Central Park had no dead trees or limbs from which large sticks could have been broken off. Marie corrected me on this. NCY red-tails have dead limbs to break off, and they have twigs and limbs of all sizes to use from other trees, too. It’s no longer fair for me to suggest the NYC nests are fundamentally different from other red-tail nests.
Except, to refresh my memories of field studies long ago (1970s), I looked up the fine photos of red-tail nests in G. Ronald Austing’s seminal 1964 “The World of the Red-tailed Hawk.” Ron Austing, another Ohioan in the Cincinnati area, became entranced with red-tails like the rest of us. He was (and is) a remarkable wildlife photographer. And like myself, he engaged in falconry with red-tails. Ron’s book, although written for a general audience, is still a major work on the species. The photography is remarkable, including the numerous telephoto shots of nests taken from carefully erected towers Ron placed next to nest trees.
It’s from these photos that I believe the wild RT nests tend to have slightly larger sticks than Pale Male’s. When I compare the unexcelled nest telephotos of Lincoln Karim with Ron Austing's photo on p. 50, the Ohio twigs do look larger than the NYC material. So I still contend that rural wild nests are made of slightly larger sticks. But whether that accounts for anything on NYC buildings is still an open question.
2. Do red-tails build nests similar to the ones they were fledged from?
Seems as though they do. But from me, that’s a useless statement because I've only seen conventional tree nests (except for two summers of cliff-nest studies in northern Nevada, where I could no watch any progeny build nests.) I think the species builds its nests primarily on instinct and materials available, not on anything learned or seen as an eyass. Eyasses are plainly stupid. They just sit there, vocalize, eat, defecate, and try to learn to fly. They don't intelligently peruse the building materials and techniques used by Mom and Pop. I think it’s all instinct.
3.Just how big are the "larger sticks" the Western Red-tails use?
I don't know. I failed to record their size when I studied those nests. At the time, it seemed to be a useless bit of information. What difference did it make? (Now, I know that it might be important, but I have no info. An unrecognized, lost opportunity.)
4. We've only seen Pale Male and Lola break twigs off trees, in their case live ones. Do your RT's take their bigger dead sticks ONLY off trees or have you ever seen them forage on the ground for them?
Another question for which I haven't the slightest answer. Frankly, in all the times I've spent looking at red-tails in the wild, I've never seen one pick up a stick off the ground, or even snap one off a tree, living or dead. And not many others have either – except you folks in Central Park where everything is concentrated in a small area, with lots of observant eyes. For me, the vast majority of the nests we studied were nests already in place, ones being reused or refurbished. Consequently only a few top-dressing sticks and lining were being added. New nests were built by new pairs, but because we were watching the nests in an area of about 600 sq miles, a new nest could go up in two or three days before it was discovered. To this day, I don't know where Ohio red-tails procure their nest materials. I see them bringing stuff to the nest, but I didn't see them collect it. An Ohio nest typically has a territory about twice the size of all of Central Park, or more.
5. Seems there are a number of variables here. There is only a certain weight of stick that a given Red-tail can carry. Perhaps only a certain diameter of dead stick that a Hawk can break off due to beak gape.

No, red-tails can carry, should they want to, a stick of remarkable size and weight. They can carry a 3/4-lb. squirrel into a tree. Even a half-pound stick would be rather large. It’s neither a weight nor size thing. It’s a question of how effective a stick will be in the nest. Red-tails have a big mouth and even much larger feet.
I've always wondered if red-tails tend to select sticks that are rough, with lots of jagged projections so as to intertwine when placed in a heap. The missing factor in all of this may not be size or weight at all. It might be the roughness or frictional characteristics of the sticks that count the most. A nest made from densely-spiked hawthorn twigs isn't likely to go anywhere unless placed upon a glassy surface. So perhaps we all need to pay attention also to stick roughness. Remember, unlike robins, red-tails do not cement their nests together. They poke sticks together in only a rudimentary fashion. The pile has to stay together pretty much by itself.
6. In regards to weight, different diameters of stick would vary depending on species (density), on moisture content(deadness), and diameter. Therefore even a big stick that was more "dead" would weigh the same as a smaller fresh one and therefore conceivably blow off. Or is there truly something about diameter as opposed to weight that would make them work better in nest building?
Larger diameter sticks, even if lighter, have more surface area rubbing on the supporting substrate (on ledges), so it takes a bigger gust of wind to blown the nest off. But this may be a very small factor. This is a mechanical engineer’s question.
In retrospect, my reference to the successes of western cliff nests may not be valid, compared to the ledges used at Central Park. The buildings of New York are almost entirely of worked, even polished stone, with low frictional qualities. The western nest ledges were rough or coarse, providing a stronger grip.
Once again, good questions – and rather fabricated answers
Pipping is not so far off. How many will it be this year? The waiting is nearly done.
John A. Blakeman

Hawk Nest Suspense

Pale Male before a Crescent Moon --April 11, 2005

The Suspense is mounting at the Hawk Bench. The window of opportunity has definitely opened. For Red-tailed Hawks, the incubation period between egg laying and egg hatching is 28 to 34 days. By most calculations today [4/13/05] is day 30.

4/13/05 -- Yesterday's Bird Report

Below is yesterday's Bird Report. The migrants are coming in, warbler by warbler. This morning, between 7 and 9 a.m. The Early Birders saw a warbler not listed below, a Black&White Warbler. We ran into Starr Saphir and her large group. She reported seeing a Golden-winged Warbler this morning, at 6:55 a.m.

Another end of winter sign: Yesterday was the last day of feeder-filling until the fall,
But winter seems to be hanging on for dear life. It was freezingin the park this morning as it was yesterday. Out with the handwarmers again.

DATE: Tuesday, 12 April 2005 LOCATION: Central Park OBSERVERS:Kathy VonHartz, Marty Sohmer, Jack Meyer REPORTED BY: Jack Meyer

Double-crested Cormorant (Lake.) Northern Shoveler (Lake.) Mourning Dove Red-bellied Woodpecker (Ramble.) Downy Woodpecker (Ramble.) Northern Flicker (Several.) Blue Jay Tree Swallow (Turtle Pond.) Northern Rough-winged Swallow (Several, Turtle Pond.) Barn Swallow (Turtle Pond.) Black-capped Chickadee (Ramble.) Tufted Titmouse (Several.) White-breasted Nuthatch (Feeders.) Brown Creeper (Turtle Pond.) Golden-crowned Kinglet (A few, Turtle Pond.) Ruby-crowned Kinglet (Several.) Blue-gray Gnatcatcher (2 or 3, ramble.) Hermit Thrush (Several.) American Robin Yellow-rumped Warbler (Several, Turtle Pond.) Pine Warbler (Several, Turtle Pond & Bow Bridge.) Palm Warbler (Several, Polish Statue.) Louisiana Waterthrush (Swedish Cottage.) Chipping Sparrow (Turtle Pond.) Savannah Sparrow (Turtle Pond.) Song Sparrow (Several.) Swamp Sparrow (Shakespeare Garden.) White-throated Sparrow (Several.) Dark-eyed Junco (Several.) Northern Cardinal Red-winged Blackbird Common Grackle House Finch (Feeders.) American Goldfinch (Several.)

Report from the Hawk Bench

Field Notes 4-12-2005

Sunset 7:33,
Temp. 49F,
Wind Var 7-10,
Prey Tally-pigeon,

AM Report-None
Elizabeth Reports nest exchange aprox. 2:30PM
3:44PM Lola in nest, she stands and turns eggs,
preens, down.
3:52Pm Lola still down in nest but preening wings.
4:00PM Lola stares W.
4:01PM Lola stands and preens. She has a large broken
feather sticking up on back above wing. She resettles,
tail to bench.
4:04PM Lola shifts head to W.
4:25PM Lola down in nest, only thing seen is errant
feather sticking up.
4:29PM Lola, head up, looks W.
4:35PM Lola stands, turns eggs, digs with feet in
cavity, then settles back down.
5:30PM Lola submerged.
5:31PM Lola, head up, alert N.
5:43PM Lola looks W, very alert.
5:45PM Lola stands, looks W, preens, then head to N,
6:02PM Pale Male from N, several crosses in front of
927, lands N end of nest, brings good sized Blue Bar
pigeon for Lola. She then stands N nest, feet on
prey, takes bites. Pale Male is in cavity of nest but
does not settle onto eggs, watches Lola...and keeps
6:05PM Lola up with prey to N disappears treeline.
Pale Male slight digging, settles onto eggs, fluffs
his feathers over them.
7:25PM Lincoln reports 1 hour and 20 minute break for
Lola before she returns to nest.

102nd St. Screech Owl Flyout: 7:40PM.

Submitted: Donegal Browne

Tuesday, April 12, 2005

Blakeman's Answer to Response to Rejoinder: [posted on 4/10]

Under the heading "Oops, you're right" John Blakeman writes:


Once again your information has very perfectly deflated some more of my conjectural explanations, this time dealing with the putative roles of pigeon spikes and larger branches for nest construction. My ideas on these aren't valid anymore. It's so important to get real information from the field, not just the mind. I'm glad to have the spikes and sticks question resolved. Mine were good ideas, if I say so myself. But they were just that, ideas. You've provided authentic local information that resolves the questions (and answers) that I proposed. This is good.

I'm particularly delighted to hear that Central Park doesn't have (at least in The Ramble) conventional urban park management where dead trees are seen as a blight and are removed. Your promotion of enlightened management policies that emulate natural forest ecosystems -- where dead trees and branches play significant ecological roles -- is very encouraging. This makes these natural areas of Central Park ever more receptive to the wonderful wildlife being observed there. Good minds. Good management. Good results.


John A. Blakeman

Monday, April 11, 2005

Screech with band

Photo of Eastern Screech-owl adult, by LINCOLN KARIM
taken in the North Woods, just before flyout at about 7:40.

If you look carefully at the foot of the owl [who is scratching his face] you may be surprised to see a band. There is a story behind that band and I will tell it as soon as things quiet down around here. But here's a hint: these screech owls didn't just find their way naturally into Central Park the way Pale Male and Lola, for instance, did.

Blakeman answers Watson:More on the Hawk Size Muddle

I'll ask the question quite a few readers may be wondering about: What exactly are the vertebrate/invertebrate generalists? I suppose these are hawks that eat insects and worms as well as meadow voles---like screech owls. Am I right? Other species of hawks or owls in this category?

Marie and Steve,
Yes, I've read Dr. Tom Cade's work on this (many years ago), but I don't have it at hand, and I don't think it much resolved the "why" of reverse sexual dimorphism in raptors, although it tended to carefully quantify the "what" of the question. I'll leave it to someone else who has more closely followed modern research developments to give a contemporary explanation of reverse sexual dimorphism in raptors.
[For those new here, virtually all raptors, both in owls nocturnally and in all diurnal raptors, hawks, falcons, eagles, others, females are larger than males, and females do most of the incubating. Why this is so remains a contentious question. In most other avian species, males are larger, but not in raptors. Why? A big question.]
Steve, I understand (as I'm sure you do, too) the correlation coefficient numbers. The -0.209 is most interesting, indicating that for this group of raptors ("vertebrate/invertebrate generalists") there is actually a very slight negative correlation between female sex and size. Makes sense, as most hawks in this category are smallish species. The other two categories are pretty significant.
Remember, a 0.0 correlation datum means that one quantity is totally unconnected to some other. One event or trait or characteristic has absolutely no connection to the other one. In the case of a -1.0 correlation, one datum is absolutely, 100% oppositely connected to the other. When one thing happens or occurs, the other never, ever does. Conversely, a 1.0 correlation means that when one thing or event occurs, another one must also always occur.
So, the 0.4 correlations of the other two categories are very strong. But again, the specific "why" of these correlations is contentious. I hope a more knowledgeable viewer could bring us up to date on this. I appreciate, Steve, that you have taken the time to sift through some of the more modern papers on the subject. Sadly, since I'm not in a university town, I don't have access to modern ornithological journals, so I'm nothing of an expert on the topic. I'm aware of its difficulties, but not of any recent resolutions of the problem.
And I thank you for your kind attribution of my Ph.D. But sadly, it's figmentary. I'm just Mr. Blakeman, a retired advanced placement biology instructor, now doing native plants landscape designs and installations. I defer to authentic Doctors of Philosophy. My expertise derives mostly from extensive hands-on field studies of red-tails, not from properly attained higher degrees or published papers.
John A. Blakeman

Understand what's happening before the Big Event: Blakeman on egg development.

For everyone impatiently awaiting the hatching of this year's brood(s), let me make a few comments on what's happening in the eggs. (This is not any sort of treatise on the subject. Those have been written by the raptor researchers who perfected the captive breeding of peregrines, where copious numbers of eggs and eyasses were produced for placement in wild nests and release at hack boxes. But those are other stories.)
As observers have noted, the incubating adult will periodically rise above the eggs and carefully turn them with her bill. This keeps egg membranes and tissues from fusing together in inappropriate configurations. This is a crucial parental duty.
We are now late into the incubation period. In the first week or so, the embryo was tiny and consumed very little dissolved oxygen, and it produced very little waste carbon dioxide. But as the embryo matured, with completely functioning organ systems, the consumption of oxygen increased significantly, and the production of carbon dioxide increased commensurately . Carbon dioxide dissolved in blood and tissue fluids renders them acid, and increased acidity (decreased pH) warps ("denatures") proteins, especially delicately-configured enzymes, which control virtually all biochemical reactions. There is a delicate balance between oxygen consumption and carbon dioxide production. And excess of the later is certain death.
Once out of the egg, the little eyass can breath freely just like we do. But while in the egg, things are gaseously rather tight. By the third and forth week, it's getting critical in there, as ever more oxygen must diffuse into the egg, and equivalent quantities of carbon dioxide must exit. Where? There is no breathing hole.
When laid, the egg shell is thick and strong, but later, the shell chemically begins to thin out and become microscopically more porous as the embryo develops, allowing increasing volumes of gases to pass through. By now, gases are passing rapidly through the porous egg shell itself, and also across the membranes beneath.
This shell thinning will be crucial, as the little eyass would not be able to puncture the egg were it to retain its initial thickness and strength. As most know, the little eyass has an "egg tooth," a small projection on the tip or top of the beak that is used to puncture the egg. This process, called pipping, takes about 24 hours or more, and it allows the lungs to slowly become accustomed to the increased oxygen of the open atmosphere. But more importantly, it allows the lungs to slowly adapt to the drying of real air. Inside the egg there is 100% humidity, and to be thrust quickly into open air causes the eyass's lungs to rapidly dehydrate.
So don't be alarmed if ever a camera is placed above the nest and an egg is seen to be broken, but the little eyass doesn't emerge. It shouldn't, until at least 24 hours after the egg tooth makes its first, tentative puncture. We needn't wish for haste here, our mammalian, parental instincts notwithstanding. Incubation and hatching will proceed at their slow, ancestral pace. It's all controlled by humidity and gas concentrations within the egg.
Today, changes within the eggs are happening at a rapid rate. Much of the egg "white," a concentration of proteins provided by the mother's single fallopian tube during egg development, is being converted into muscles, skin, and feathers. The egg's "yolk,' a supply of energy-dense fats, is also being depleted as the eyass grows. The white provides the body-building materials, and the yolk provides the energy to power it all. At the end, only the little hawk and a thinned egg shell will be left, and then it will be time to start the pipping process.
In short, the eggs aren't sitting there just being warmed. Some remarkable, hidden physiology is taking place. We'll be seeing the results of this not long from now.
I'm beginning to get some anticipatory excitement. Who could decide to disregard all of this? I've watched it now for over 35 years, and it's still always a thrill. I'm glad so many in New York City will be able to once again watch the appearance and development of young red-tailed hawks . It's good for everyone to have some visible, personal connections to things in nature, and what could be more noble and inspiring than watching another family of red-tailed hawks be produced? What a privilege this is. I thank all of those in Central Park who are watching and describing these events for all of us.
John A. Blakeman

Correlation coefficient Explained!

In a posting yesterday (More [and more technical] Info) I challenged Steve Watson to explain the term "correlation coefficient" so that everyone would understand. He's done it! At least I think I finally understand it.

Hi, Marie,

A correlation coefficient simply indicates whether or not there is a relationship between two datasets. In this case I used the simplest one, denoted r, which indicates whether or not there is a *linear* relationship. A value of 1 would indicate a perfect linear relationship, while a value of -1 would indicate a perfect linear relationship with negative slope (as one value goes higher, the other goes lower). 0 indicates no linear relationship at all. The closer the value is to 1 or -1, the more closely the two datasets show a linear relationship.

The thing to watch out for is that this only indicates the presence or absence of a linear relationship...the two datasets could be related in many other ways (non-linear polynomial, for example) and this test would not show that.

Also, it's of utmost importance to remember the phrase "correlation does not imply causation"! This was just a test to see if such a simple relationship *might* exist.

Notes from the Hawk Bench and a screech-owl note

Notes From The Bench 4/10/2005

Sunset 7:30PM,
Temp. 73F,
Wind variable 7-10MPH,
Humidity 22%,
Prey Tally- None seen,

Early Report: Nest exchange approx. 11AM. Bill
reports Pale Male perched on the Carlyle from approx.
2:15 to 3:15PM.

3:59PM Hawk on nest, head to wall,E, tail to bench, W.
Only small portion of tail visible. Report from the
bench said it was Lola but...? Stubby the Drake
Mallard is in residence in the Boat Pond. He now
knows his name and comes when called for peanuts.
4:17PM Hawk has not moved a feather, same position as
4:30PM Lola arrives on the N end of nest. (It was
PALE MALE tending the nest Not Lola.) Pale Male stands
and takes a beak full of dry needles/grass(?) from
rear edge of nest and places in concave.
4:31PM Pale Male up and off nest. Lola leans over and
turns eggs. Pale Male does ascending circles above
Linda until out of sight. Lola settles into nest,
facing W, very alert.
4:34PM Pale Male seen landing by Sam on rear of
4:47PM Lola head up, looks N.
4:50PM Pale Male perched Oreo antenna.
4:51PM Lola looking W.
5:00PM Pale Male up and to W.
5:05PM Much sun on nest, Lola facing E, tail to nest.
5:26PM Pale Male perched Carlyle, Lamp 1.
6:00PM Lola head N, Pale Male perched Carlyle Lamp 4.
Tourist brings debilitated Ruby-crowned Kinglet to
bench. Noreen calls Vivian the rehabber. Kinglet to
be delivered by tourist to Vivian.
6:20PM Exit

102nd Street Screech Owl Flyout-staggered from 7:33PM
to 7:39PM. Young owls practicing adult call. Though
still do begging wing flaps when fed by parent owl.

Submitted-Donegal Browne

An Amusing Article

By Martin Crutsinger
Associated Press
April 8, 2005

By Martin Crutsinger
Associated Press
April 8, 2005

WASHINGTON - The Secret Service, which has the job of guarding the
and other dignitaries, now has a new temporary duty ‹ protecting a mother
duck and her nine eggs.

The duck, a brown mallard with white markings, has had several names
suggested by Treasury Department people, including "Quacks Reform,"
"T-Bill," and "Duck Cheney." It has built a nest in a mulch pile right at
the main entrance to the Treasury Department on Pennsylvania Avenue.

The Secret Service's uniformed division, which provides protection for the
White House and Treasury building, has set up metal guard rails to protect
the nest, which has attracted the notice of tourists on their way to see
White House.

The duck has been provided with a water bowl and seems oblivious to all the
attention, sitting calmly on its nest on top of the mulch pile that
surrounds one of the new trees planted along Pennsylvania Avenue as part of
a renovation project.

Treasury Secretary John Snow stopped to pay his respects this week on the
way back from a congressional hearing, Treasury spokesman Rob Nichols said

"He had been briefed on the duck and he stopped to pay a visit," said

The eggs are expected to hatch the last week of April at which time the
will be relocated nearer water. But until then, the duck will occupy some
Washington's prime real estate.

"Foreign leaders, members of Congress, everybody who visits Treasury has to
pass by the duck," Nichols said.

WASHINGTON - The Secret Service, which has the job of guarding the
and other dignitaries, now has a new temporary duty ‹ protecting a mother
duck and her nine eggs.

The duck, a brown mallard with white markings, has had several names
suggested by Treasury Department people, including "Quacks Reform,"
"T-Bill," and "Duck Cheney." It has built a nest in a mulch pile right at
the main entrance to the Treasury Department on Pennsylvania Avenue.

The Secret Service's uniformed division, which provides protection for the
White House and Treasury building, has set up metal guard rails to protect
the nest, which has attracted the notice of tourists on their way to see
White House.

The duck has been provided with a water bowl and seems oblivious to all the
attention, sitting calmly on its nest on top of the mulch pile that
surrounds one of the new trees planted along Pennsylvania Avenue as part of
a renovation project.

Treasury Secretary John Snow stopped to pay his respects this week on the
way back from a congressional hearing, Treasury spokesman Rob Nichols said

"He had been briefed on the duck and he stopped to pay a visit," said

The eggs are expected to hatch the last week of April at which time the
will be relocated nearer water. But until then, the duck will occupy some
Washington's prime real estate.

"Foreign leaders, members of Congress, everybody who visits Treasury has to
pass by the duck," Nichols said.

Sunday, April 10, 2005

Field Notes from the Hawk Bench --and a quick note about the screech owls

Field Notes From The Bench
Saturday, 4/09/2005

photo by Lincoln Karim 6April05
Screech-owl after Flyout

Sunset 7:29PM,
Temp. 64F,
Wind ESE 7-12MPH,
Gusts to 20MPH,
Prey Tally-Blue Bar Pigeon

Early Report-Commissioner Kelly watches the Hawks.
Ric gives him a photograph. The Boat Pond water is
still remarkably blue.
5:02PM Pale Male on lamp 1, Carlyle roof. Lola
sitting nest.
5:03PM Lola stands, beak to concave of nest, some
small digging.
5:05PM Lola settles into nest, tail to bench.
5:08PM Lola shifts head to bench, alert to W.
5:09PM Lola, head full up, eyes due W., Pale Male Lamp
1 Carlyle.
5:22PM Pale Male still lamp 2. Lola still looks W, now
through nest twigs.
5:28PM Pale Male gone. Mallard count:4
5:32PM Lola disappears into nest.
5:36PM Lola stands up, preens chest, shoulders,
5:38PM Lola down.
5:52PM Lola alert to W.
6:19PM Lola's head completely visible, looking S.
6:28PM Pale Male lands left nest, half Blue Bar pigeon
to Lola. Lola takes several bites tail to bench,
while Pale Male alert, then she's up, taking her
pigeon, flies N disappears into trees and past Oreo.
6:32PM Pale Male surveys nest, turns eggs, digs,
settles in tail to N, head to S.
6:42PM Lola returns, gets Pale Male off eggs. ?
6:43PM Pale Male up.
6:45PM Lola settles in.
6:51PM Pale Male perched top railing Green Shade
6:55PM Sun off nest.
7:05PM Golden Light Fifth Ave.
Screech Owl family flyout, 7:42PM

Submitted-Donegal Browne

Blakeman's Response to my 4/9 rejoinder, and my new response.

In response to my comment at the end of Blakemans letter published here under the heading of Blakeman on the proliferation of CP Redtails the raptor expert wrote:

Yes, I've discounted an essential role for the nest-supporting pigeon spikes. I've done this because Western red-tails frequently and successfully nest on bare rock ledges that offer no innate protection from winds and other nest-destroying natural forces. I still tend to believe that until a pair learns to properly line a nest, eggs can cool.
But this will be a wrong explanation when a New York ledge nest gets simply blown away. And your accurate noting of the older age of some of the other failed CP parents negates my contention. If I had to bet on which explanation holds, I think it's yours.
Here's a thought that just came to mind. Are NYC red-tail nests atypical because there are no dead trees from which larger branches can be snapped off and used to construct heavier nests? Looking back, it seems to me that the 927 nest has been constructed of twigs, the diameter of a pencil or less. I seem to recall that wild rural nest have a much larger component of sticks that approach the diameter of one's little finger or larger, real sticks not twigs.. Larger branches can't be snapped off a living, healthy tree by a red-tail. But large, heavy sticks can be easily broken off dead trees, where the bark is already falling away and the wood is brittle.
So here's another unique NYC factor to consider. Has good urban forestry, the removal of all dead standing trees, forced the birds to construct nests with smaller twigs from living branches, which are much less heavy than the larger sticks and branches used in rural nests? If this is so, the pigeon spikes become essential in keeping the twig nest from blowing away. It may be that NYC red-tail nests are not as heavy as wild rural ones because bigger, heavier branches that could be snapped off simply aren't available in Central Park.
Does the absence of dead trees indirectly dictate that NYC red-tails must nest on ledges with supporting pigeon spikes?
And here's a good one. Are pigeon spikes themselves the fundamental reason RTs have been able to invade and persist in NYC? Over the years, have a few errant red-tails attempted to construct building-ledge nests that quickly blew away, leaving the birds stranded (and unnoticed)? Was the introduction of stainless steel pigeon spikes sometime in the 1970s or 80s (I presume) the deciding factor in recent nest successes? Were pigeon spikes the thingamabob that did the job?
After leaf-out in May, look around Central Park and see if there are any dead trees from which larger branches could be snapped off next winter. This could be a major factor in our story. Western ledge nests don't get blown away, and I think they are made of much larger sticks. These may not be available in New York.
John A. Blakeman

Marie's answer:

Dear John,

We've got to get you to visit Central Park! We keep providing more info that you would see for yourself if you just took a walk in the Ramble.

In regard to the absence of dead trees: I'd say that there are plenty of dead trees in the park's woodlands. With the guidance of the Woodlands Advisory Board, of which I am a long-time member, the Ramble, the North Woods, and other small wooded areas are maintained for usefulness to wildlife as well as for public aesthetics. Thus many dead trees are left in place as nesting places for woodpeckers, chickadees etc., just so long as they don't pose a safety hazard to the public. Dead limbs hanging over public pathways are removed , of course. But there are brushpiles around, and many large limbs on the ground in the park's woodlands. There is a deliberate policy to avoid a manicured, horticultural look in these parts of the park.

As for the anti-pigeon spikes as an important factor: I only know of a single site where anti-pigeon spikes have led to a nesting success: Pale Male's ledge at 927 Fifth. I haven't seen any spikes anywhere else. That is the likely reason why all the other attempts of nest-building on various ledges on the periphery of the park have failed, year after year. No spikes.

I often thought that the doctors at Mt. Sinai Hospital should have installed spikes on the ledge where a pair of hawks made nesting attempts three years in a row. I know the doctors were intrigued by the hawks and wrote about them in some hospital newsletter. But those hawks only succeeded last year, when they finally wised up and built a nest in a tree due west of Sinai. [Of course we're not absolutely sure the Mt. Sinai pair are the same hawks as the one who nested in the tree in mid-park around 97th St. But the male we called Pale Male III was a very light-headed bird, and my own hunch is that it was the same pair.]

More [and more technical] info about Reverse Sexual Dimorphism from Steve Watson to John Blakeman

Steve Watson, the Kestrelcam correspondent, sends in some results from his research into the reverse sexual dimorphism enigma -- that is, why female raptors are bigger than males of the various species. He intended his letter for Blakeman, but since he sent it along, I am posting it for those readers who studied statistics somewhere along the line.

Here's a challenge for Watson: for those who haven't taken a course in statistics, can you explain in ordinary language what a correlation coefficient is? [After all, I just explained in ordinary language what reverse sexual dimorphism is!] At least interpret the numbers in the final paragraph

Hi, Marie,

... here's some more info [about reverse sexual dimorphism in raptors]: .

In my research on kestrels (and specifically, dimorphism in their eggs), I found an article which summarized some average weights for males and females, by species, and their ratios, broken down by foraging type. This partially responded to my question about increasing dimorphism ratio as a function of increasing body mass, but the results appear less than conclusive to me (although, frankly, I'm not a statistician, so I'll defer proper analysis to the experts). Anyway, I've attached a chart I made from the data, just thought it might be of interest to John and perhaps others. The paper is Anderson, J. et al., Prey Size Influences Female Competitive Dominance in Nestling American Kestrels (Falco Sparverius), Ecology 74(2), 1993, pp. 367-376. The table summarizes Cade (1982) and Kemp (1987), all of which with I'm sure Dr. Blakeman is familiar.

As a bit of additional info for John, I did a quick correlation coefficient on these three groups (correlating female mass to sex ratio) and got -.209, .419 and .426 for vertebrate/invertebrate generalists, vertebrate generalists and bird/bat specialists, respectively.