Friday, February 25, 2005

"SOMETHING IS STUCK..."

Re "SOMETHING IS STUCK..."
No, it's parts of pigeon (food) stuck to his beak...Lincoln

A reader of this web site, Marilyn Fifer, sent John Blakeman some reports about various recent raptor matters, among them, the red-footed falcon appearance on Martha's Vinyard last summer, the Bald Eagle re-introduction effort at Inwood Park last year, and an incident of red-tail-peregrine-falcon interaction and predation. He sent me a copy of his response to her. It is below:


Marilyn,

I'm familiar with the red-footed falcon incident on Martha's vineyard. Just plainly weird -- including the inordinate efforts of "listers" to try and count the specimen. Amazing what storm winds blow in.

I was not aware of the NYC bald eagle restoration project. The population of BEs is exploding everywhere. We have over a 100 nests and over 300 bald eagles in Ohio. What's been discovered as the limiting factor, one that may keep the birds from nesting on or near Manhattan, is the availability of large nest trees. If those aren't there, the birds simply can't and won't nest.

They will, however, become remarkably tolerant of human disturbance. We had a pair here nest in someone's back yard, produced three eaglets, all of which dropped down on to the backyard trampoline and began jumping up and down on it. We have photos to prove.

And any peregrine that wants to kill a red-tail, probably can, if the hawk is struck up in the air. The peregrine moves like a powerful fighter plane. The red-tail like a muscular bomber. But a red-tail will absolutely attempt to steal a falcon eyass on the nest. Easy pickings if the parent falcons aren't around to defend.

Thanks much.

Sincerely,

John A. Blakeman

A COMMENT FROM JOHN BLAKEMAN and

Within an hour of posting the photo and exchange of e-mails below. concerning Pale Male's beak condition, I received two responses; the first was a most informative and welcome discussion of redtail table manners from John Blakeman. The other, an emotional comment that echoed my own reaction to the photo, from Linda Most of Tallahassee, Florida.

Marie,

One added note about the "stuff" on Pale Male's beak while feeding. Lincoln was absolutely correct, it's just harmless remnants of the pigeon he's consuming.

As I think I mentioned previously, hawks don't eat with much decorum. They'd be tossed out of all New York restaurants. Feathers or fur, skin, blood, and other disagreeable body parts are just tossed in all directions. And they try to consume as much in one bite as possible. It's really gross to watch a red-tail consume it's favored food (out in rural areas), the ubiquitous meadow vole. If it's not in a hurry, it will pull the rodent apart in several large pieces. But if in haste, it will try to swallow the animal in its entirety. One gulp gets the vole into the mouth, and a second, seemingly labored one, gets the vole all the way down.

Where were the mothers of these birds when the should have been teaching good table manners? Well, they were out looking for more food to feed the ravenous eyasses growing up on the nest. And when there are two or three, as has been the case of the 927 nest, the youngsters can get a bit possessive about the food dropped on to the nest. Fine culinary deportment is just not a part of a red-tail's behavioral repertoire.

So if any hawk watchers get to see a bird feed, as in Lincoln's superb photo (Aren't they all just spectacular?), don't be alarmed at the wild messiness of it all.

But at the end, our raptorial friends do exhibit a final gesture of cleanliness. Almost universally the hawk will do two things after feeding. The first is to "feak," to carefully wipe her beak back and forth on the branch she's sitting on. This wipes off all the food leavings, except for some blood stains which might remain. One of the first things I always look at when trapping a wild red-tail is to examine the beak and talons for whatever remnants of a recent meal might be present. Often times, some vole or rabbit hairs are lodged between the toes, or are found adhering to a feather. But the birds, especially adults, are pretty fastidious after eating.

The last thing the bird does after eating and feaking, is to "rouse." After stropping its beak clean, feaking, the bird then straightens up and shakes its entire body, just like a wet dog after it crawls out of the pond. This rousing (a falconer's term) re-settles the feathers into their natural places. The bird then feels satisfied and contented. We falconers know that if we don't see our birds rousing from time to time, especially after a meal, something is wrong. Rousing indicates a happy hawk.

Pale Male surely feaked and roused after his fine pigeon repast. Life is good for him in Central Park and at 927 Park Ave. He rouses often.

Sincerely,

John A. Blakeman

Thursday, February 24, 2005

JOHN BLAKEMAN ANSWERS SOME GOOD QUESTIONS

Marie,

Here are my answers, however incomplete, to the wonderful ones from Donna Browne. Donna obviously has some experience and thinks like a good field biologist. Here are her questions.

Donna:
“Does anyone (Blakeman?) know how prevalent Pale Male's genetic coloration is or whether it is gender linked?”

JB:
I've watched and trapped a pile of red-tails in 35 years, and I think I've seen just one or two with light-colored heads. In northern Ohio, I'm certain that the coloration isn't common. But it’s interesting to note that eastern populations or races of the red-tail tend to be lighter-colored, western ones darker. So this may be a local genetic tendency. Someone from the Hawk Mountain, or better, Cape May, New Jersey, hawk migration stations could better answer this.

Donna:
“I find it interesting that the Pale Male progeny of Pale coloration, at least the ones I've heard about, are male.”

JB:
As to the color being sex-associated, I have no real information on that, either. But I'm betting that it’s not sex related. I know of no other sexual dimorphism (differences between the sexes) in red-tails that are color based. It’s all size, as far as I know. Sure would be interesting to find out, though. Let’s look for a blond-feathered female.

Donna:
"Does one gender have more of a tendency to range? Did I not read that a female RT not only takes into account the male himself but also his nest site and territory in making her choice?”

JB:
For this, I personally think there is no doubt that females mate not just with the male himself, but with all the territorial accouterments he brings to her attention, including good perch sites, abundant prey, absence of “significant others” (competing adjacent hawks) and all the other things good mothers consider. No, it’s not just sex (we males do have a hard time figuring that out). As I think I mentioned before, the paired hawks are as much mated to their territories as they are to each other.

Reminder from Marie: Don't forget that when John Blakeman uses the word "mate" he is not referring to the sex act. Scroll down for a discussion of "mate" vs. "copulate"

Donna:
“Does it make sense that once a male has a nice nest site and territory that he would range less far than a female who's looking for a male with a nice nest site. Therefore would more of the female RT's in the park be non-related. OR...As half siblings have been known to procreate successfully in other species, and Pale Male has had four mates...?”

JB:
Wow. I like this thinking. It does make absolute sense that young males should not disperse as far as females. Once a male claims a territory and starts circling in the air (raptorial strutting, as it were) to attract an on-the-look female, he certainly isn't going drift off. He’s going to stay right in the area he claims and do all he can to attract passing females..He’s not going to leave his claimed territory to try to bring in any distant female. He can only attract passing or wandering females. He will stay put.

But the questions for our Central Park birds is a) really where have they spent their first fall and winter, and b) have they then come back to their natal area? Without banding data, it’s impossible to tell. The core issue, again, may revolve around prey availability. If the fledged young learned in the summer that CP just has piles of available food, they will never forget that, and when hungry, may attempt to return, even at the threat of being driven off again by mom and pop.

Where do all the CP fledglings disperse to? Just up the river a bit, or do they drift off to all parts of the northeast or elsewhere? One thing falconers know is that first-year birds have a very strong migratory urge. Those of us flying new-trapped first-year red-tails have to be particularly watchful of weather when hunting our birds in late September and early October. Depending on the personality and training of the particular bird, a falconer may not be advised to fly his hawk on a crystal clear, warm, slightly windy day in late September. A red-tail just loves to spiral up in the thermals or such weather, and in just two or three minutes she can be at 500 or a thousand feet. In most cases, the falconer can lure her back down with a tidbit of fresh meat on the raised fist. But from time to time the hawk just sets her wings and starts to drift southward, never to be seen again. Experienced falconry birds being flown in subsequent years seldom, if ever do this. First year red-tails do have a strong autumnal migratory urge. The CP offspring may spend their winters in Georgia or Florida (like a some humans).

Donna:
"There are so many questions and none can be answered about the Central Park Red-tails until we figure out a way to tell them apart without banding them. They currently trust us; we can't blow that. Wait. They can now gender test birds using a feather. I wonder if that is actual DNA testing or testing for testosterone? "

JB:
Once again, exceptional thinking. I'm not an expert on this, but I do believe if someone were to collect a feather that was surely seen to fall from a known bird’s body, DNA or chromosome characterization may be possible. But the problem is that first-year birds don't drop any feathers until the spring after they fledged. That doesn't do us any good, as they may be anywhere east of the Mississippi then.

Trapping and banding is the only good solution, but this won't be possible (or advisable) in NYC. Be assured that when properly done, it does not disrupt the hawk’s “trust.” What it does do is make the bird almost impossible to ever trap again. Hawks remember remarkable details of how they capture food, and trapping always entices their approach with food. When trapped, they will never in a decade ever forget what brought them to the trap. Only when a previously trapped bird is starving will it ever approach a moused trap again. And again, raptor traps use no steel or springs, and cause no harm, pain, or injury to the hawk whatsoever. But trapping in Central Park is utterly out of the question.

There is only one other ID method that could be considered. Lincoln Karim’s remarkable photos of the red-tailed hawks of Central Park are, without doubt, the finest photographs of this species in the wild. I am continually awed. Here’s a photographic ID consideration, if possible.

We can't much tell birds by their feathers, except as to general patterns and colors. Between the immature and adult feathers, between the first and second years, there is far too much variation to connect a second year bird with a previously known bird on the nest.. But there is one structural feature that doesn't vary from molt to molt. It’s the bird’s “scale print,” the individually unique pattern of the scales of the legs. An extreme close up of these when a hawk is perched can allow identification any time later in the bird’s life – if another telescopic macro shot of the same leg could be taken. It’s a daunting task, but one that should be considered. Let’s think how this might be facilitated.

Mary Lewis's Question:
And now for a final fine question that was forwarded to me. Mary Lewis learned that Canada geese, during incubation, warm up their naked feet to help keep the eggs warm. She wondered if there was any evidence for this in our red-tails. In late March it’s pretty cold up way up there in the wind.

But no, I don't think heat transfer out of the legs or feet of the hawk has any significant warming effects. Here’s why. First, unlike a goose, a hawk’s foot doesn't have much surface area. And when they begin to sit, they fold up their feet into closed fists. Sitting hawks, especially our giant red-tails, are particularly attentive to this. They are very careful to fold the talons back under the toes, so as not to inadvertently poke a delicate egg while sitting or standing on the nest. If anyone gets to watch a sitting exchange, when one hawk rises to allow the mate to take over incubation, watch the deliberate delicacy with which both birds move their legs and feet. They will place their legs in the nest next to the eggs, but not necessarily in direct contact with them. It’s the transferred warmth of the naked abdominal brood patch that does the job.

Sincerely,

John A. Blakeman

Tuesday, February 22, 2005

Destruction of Suburban Woodlands

Marilyn Fifer sent the following letter, which I forwarded to John Blakeman. He sent a reply, which follows the letter.


Dear Ms Winn:

...Recently, you and John Blakeman discussed an increase of the urban RTH population; however the issue of encroachment by development /destruction of suburban woodlands had not been represented as a cause and effect. This loss of habitat /food supply forces the RTH to search for new territory. NYC may be to hawks what the Americas were to Columbus.

My husband and I are aware of raptor population in (Northern) Queens, Nassau and Bronx county. The newest resident in our neighborhood is a red tail who considers the Ft. Totten woodlands as part of his territory. While driving on the parkways/expressways in Nassau county, we are on 'hawk patrol' looking for raptors perched on top of lamp posts or trees. We have espied red tails (including a mated pair) and what appear to be Cooper's and/or Sharp-Shinned hawks. We are members of the WCS and visit the Bronx Zoo every weekend. A few red tails consider the zoo's 265 acres as part of their territory.

They're out there!

Thank you for your wonderful web site, and a thank you to John Blakeman for sharing his wealth of knowledge with us.

Best wishes,
Marilyn Fifer



Dear Marie and Marilyn,

The destruction of suburban woodlands and forests is not a significant population stress for red-tails for the following reason. RTs simply can't and don't live in extensively forested areas. The big birds absolutely require large, open hunting areas. Any area that is much more than 50% forest is not ideal. Too little meadow rodent habitat, and too many trees, around which the red-tail has difficulty flying when hunting.

In presettlement times, before European destruction of the great forests of the East (including my Ohio), red-tailed hawks were very rare, living only on the edge of a few forest openings. In Ohio, about 4% of the state was open prairies (as was much of Long Island). The red-tail lived only on the edges of these large grasslands. Tens of thousands of square miles of closed forests had no red-tails. (And heavily-wooded central Pennsylvania to this day has few nesting red-tails.)

In short, there are more red-tails today than ever before. In early times, the birds were rare in the East because most of it was dense forest. When the forests were converted to meadows and pastures, the red-tail population quickly expanded into these new areas (much as the species has in NYC recently). But because everyone had free-ranging chickens, and hungry immature red-tails would kill these easy delights, the hawks were shot.

Only recently has the shooting and trapping of hawks essentially ended. The only major human killers of red-tails today are motor vehicles, and then usually only clumsy immatures out on initial summer hunting adventures.

The thought that moderns continue to destroy wildlife habitat, thereby forcing the extirpated animals into marginal or urban areas seems reasonable. But whether it's white-tailed deer, or our red-tailed hawks, this virtually never happens.

First, how long does it take to convert a rural district to shopping malls and housing developments? It's not the 3-5 years deer commonly live out their lives, nor even the 10-15 years adult red-tails live. And with both deer and red-tails, most offspring never live through their first years.

The thought that suburban development drives animals into marginal habitats seems reasonable, but it's wrong for this reason. The concept presumes that out in nature there is a generally fixed number of animals.When the areas they live in are destroyed, the animals no longer have a place to live and must try to survive in remaining, degraded habitats.

But nature never has fixed numbers of animals. The size of animal populations is always a result of the amount of available habitat. If that declines (as it does with development) the number of animals simply declines. The animals don't move somewhere else. They die. If new habitats are created (or found, as with Central Park), populations will expand there. Massive development has certainly led to a decline of many species, and sprawl reduces locally-available habitat. But by itself, development and sprawl haven't forced animals to take up residence elsewhere. Most of the displaced animals, whether voles or red-tailed hawks, have simply died off. Our Central Park hawks haven't moved there because someone built a new mall over in Jersey. That mall, by itself, is one thousandth the area needed by a wild rural pair. Even a new 100-acre housing development isn't a massive portion of a pair's territory. Urban sprawl is decidedly detrimental to wildlife populations, but primarily because they destroy habitat, not that they drive away wildlife residents.

Marilyn, I'm afraid that you've acquired the same habit the rest of us have, who frequently travel hawk-populated roadways. Red-tails just love to sit on utility poles and other perches overlooking highway rights-of-way. These grassy swards are prime habitat for meadow voles, and red-tails are habitual hunters in these areas. They tend to take the same hunting perches at the same time of day for extended periods, often several weeks or more. For me, it's just such a pleasure to see perched red-tails along highways. They make travel a bit more interesting. My wife and I just returned Saturday afternoon from a Cleveland Playhouse show 50 miles away. We counted five red-tail nests and close to a dozen birds perched nearby. Shouldn't we feel sorry for the hundreds of other motorists who passed by without seeing any of these regal birds? Glad to hear that others are seeing local red-tails in the greater New York area. I like your term, "Hawk Patrol." I'll continue my patrols.

Sincerely,

John A. Blakeman

Monday, February 21, 2005

A VERY PERSUASIVE RESPONSE FROM JOHN BLAKEMAN TO MY HYPOTHESIS ABOUT PALE MALE'S PROGENY

Marie,

Here are my requested thoughts from your very interesting post.

First, don't anyone apologize or diminish any of their own thoughts or explanations on this. I may be some kind of red-tail “expert,” but everyone should question, or at least remain open, about most of what I contend. If I had time, or were writing a book on the matter, I'd delineate what I perceive to be “fact,“ as opposed to my evidence-based prognostications. Most of what I post is pretty sound material (in my mind and experience), and I would be able to defend those notions with abundant evidence. Other thoughts are just those, mere thoughts.

I'm taking the liberty here to lay out all of my thoughts publicly, allowing everyone to follow the development of my personal explanations for the Central Park red-tailed hawk saga. In strict science, all of this should remain obscured, to be revealed only upon the publication of a paper. But here, we are carrying on a must delightful public discourse, and all thoughts should be out on this expanding table of ideas. Again, don't anyone be reluctant to offer his or her thoughts and observations.

I still contend that most of the red-tails fledged at 927 Park Ave never attained adulthood. Why do I believe that? Because that’s the case with every studied population of immature red-tails. The banding data overwhelmingly support this, and I've watched any number of mid-summer red-tails get pushed out of their natal territories in July and August. I've trapped these birds for banding, and they are extremely weak, approaching starvation.

The following explanation would be far too long to entirely describe, but let me just touch on the survival challenges that must be met by a young red-tail who, for the first time, is no longer being fed by mom and pop. The first challenge for a youngster first on her own is to actually find food. Yes, red-tails have remarkable eyesight. Innately, they can focus and peer telescopically with great resolution. That’s all fine. But they actually have no innate or instinctive capabilities to actually find where food exists. They have to learn where and when mice, voles, rats, and other potential prey can be both seen and captured. This can take weeks to learn.

Next, the inexperienced hawks have to learn how to capture the prey. This might seem to be the least of their problems, given their strong talons and wings. But no one more than falconers knows how clumsy and inexpert immature summer red-tails can be in actually grabbing food. The hawk has all the equipment, the talons, the strong legs, the powerful wings, and telescopic eyes.. But until all of these are perfectly coordinated, hunting efforts are profoundly inept. I've seen this awkwardness in many summer-trapped falconry hawks. Many of these, I'm sure, would have starved had I not trapped them and started to train them to hunt successfully on their own. While in this falconry training, I provided the food they could not capture on their own.

Lastly, a kicked-out August or September young red-tail has to also find a vacant habitat where it can perch, hunt, and roost. In August and September, adults don't want any young birds in their territories because for the first time all summer, prey becomes harder to find. But late summer, there aren't anymore young robins, rabbits, or other abundant, easy-to-catch prey. In May and June, the days are long (lots of hours to hunt), and vulnerable prey are abundant. None of that’s the case in August and September, when the majority of young red-tails perish.

So, I still firmly believe that the majority of the eyasses sired by Pale Male never attained adulthood. They never lived long enough to molt out a red tail in their second summers.

But right here, I'd better inject an alternate explanation about the possibility that the pale-headed red-tails seen in Central Park might be 927 progeny. Elsewhere, I elaborated on why these birds are not likely to be so, based upon general red-tail biology and evolutionary tendencies. I still think this is the more likely explanation, that the new birds’ parents are not Pale Male, Lola, or any Pale Male’s other consorts.

But if Central Park today can support three nesting pairs, along with the recently-observed five immatures – 11 hawks that have to each capture and consume about 120 grams of flesh every day – then, perhaps, Pale Male and Lola haven't been very astute in driving off their youngsters. If Central Park has a continuing abundance of food, perhaps, then, the young weren't driven off. I continue to believe that most still died from hunting inexperience. But I have to now admit that there is a greater possibility that at least some of the other Central Park red-tails might be 927 offspring.

For those who might see this as a wonderful, romantic turn, I assure you it’s not. The constraints of genetic non-variability or uniformity would still be detrimental, especially if the Central Park red-tailed hawk population were to begin to inbreed. If that’s so, if most of the CP red-tails descend from a single parent (the great sire Pale Male), things could get very ugly in just a generation or two. The first thing to go wrong would probably be behavior fitness. Inbred hawks would be less likely to learn to effectively and safely hunt. Secondly, they most likely would not go through all the nuanced rituals of pair-bonding, nesting, and the successful rearing of offspring. Getting all of this just so is a remarkable ballet, one that everyone is watching once again. It doesn't take much to upset the successful but delicate interactions between both mated adults and their offspring. By nature, these birds are quick, muscular killers. All of the mating, copulating, incubating, and rearing behaviors of nesting pairs is contrary to the birds’ innate, day to day nature. I fear that inbreeding would easily disrupt this delicate balance between the restraints of pairing and the killing instincts of normal, day to day life.

It’s easy, even convenient, to believe that all of what were are seeing is the real nature of the red-tailed hawk. The birds appear to be loving, devoted mates and parents. These they are, of course. But how many have seen a red-tail actually hunt down and brutally kill a rat or pigeon or squirrel? To see this close at hand, as I have so many times when my falconry red-tails have taken cottontail rabbits, is to fully understand that these birds are carnivorous predators. They are, by nature, killers, ever bit as much as the lions of the African plains or the brown bears of Alaska.

On another point, I don't believe Pale Male is an evolutionary breakthrough. He’s nested for over a decade; a nice achievement, but one shared by thousands of other red-tails. His nesting record is quite typical for the species. On the other hand, he certainly has learned to succeed in the unique environment. But this, alone, is not so remarkable because the species itself has learned to live in so many habitats. The red-tailed hawk lives and successfully breeds in virtually every habitat (except closed forests) from the edge of the Arctic all the way to the Mexican desert. In the West, it nests on cliff sides structurally not much different from 927 Park Ave. Pale Male’s ability to adapt to NYC and Central Park, I believe, merely reflects the general adaptability of his species.

Once again, banding of the offspring, to allow accurate identification, would bring real light to this question.

Let’s hear the thoughts of others.

Sincerely,


John A. Blakeman

JOHN BLAKEMAN ON PREENING AND ECTOPARASITES

Marie,

Lisa’s remarks on the role of the “essential oils” emanating from the pine needles are significant. I thought about her comments, and this came to me.

Red-tails that aren't incubating spend up to an hour or more most mornings preening. In doing so, they transfer oil from a gland on their rump to the feathers of the body. Hawk watchers can often see this. The bird pokes her bill down into the feathers of her upper rump, where she gets a microscopic layer of the feather oil on the beak. She then strops the oil-laden beak on feathers all over her body.

This daily feather maintenance is absolutely essential. Remember, on the wettest, windiest days, our red-tails aren't passing the time inside any dry shelter. They are stuck out there in all of the worst weather, and if their feathers aren't properly oiled, rain will soak through and quickly kill the hawk by hypothermia. Daily preening is not for beauty.

Like most birds, our hawks are similar to turtles, in that they carry their houses with them where ever they go. Their houses, of course, are the feathers, which keep heat in and water out.

How might pine needles be involved in all of this? Lisa’s thoughts are particularly cogent. A sitting, incubating red-tail does, indeed, preen, but she can't spend an hour on her feet doing this. She’s pretty much bed- or nest-ridden. She still has to get the oil from her oil gland out over her feathers. But because she has to spend most of her time with her naked belly skin (the brood patch) tucked right up to the developing eggs, preening time and effort becomes a bit problematic.

Here is where the pine needles might enter. When red-tails preen, they not only spread protective feather oils, but they also comb out with their beaks very tiny feather lice. These very tiny bugs actually eat hawk body or contour feathers. The feather lice prefer to eat the white, un-pigmented portions of the brown body feathers. Preening greatly limits the damage feather lice can cause. The aromatic emanations of pine needles might restrict the feather lice while sitting on the nest.. Therefore, the sitting red-tail can apportion her meager preening time to only spreading feather oil. With the pine needles, she perhaps needn't spend much time combing out the feather lice. The pine needles may drive the lice away.

Red-tails have another arthropod ectoparasite, the hippoboscid fly. I have never found one of these large, slow, flattened flies on a healthy adult.. But virtually every immature bird has them. These things are the size of large house fly, but are very flattened. They don't fly very fast, but they move between the layers of feathers with great alacrity. These things live on blood they suck from their hawk hosts, and can be a real problem when the young red-tail begins to decline due to poor health or starvation. A healthy, experienced adult learns how to grab and kill the bugs with their beaks. But the newly-fledged youngsters don't recognize the pest, and they can run rather profligately between the feather layers. A single dose of parrot ectoparasite spray kills the hippoboscids in my captive birds. They never come back. The aromatic gases or odors coming off the pine needles may drive the hippoboscids off the incubating parents. They surely don't have much time to be poking around with their bills chasing these feather flies while still trying to maintain proper temperatures in the eggs beneath.

This would be a wonderful experimental study by an undergraduate ornithology student. Devise some trials where pine needles are placed next to cultures of feather lice and hippoboscids and record their reactions. This may solve the “Why evergreen sprigs?” question. Good thinking Lisa, something I hadn't considered.

One last note. For those watching the birds up close, check to see if the bird you are watching has evidence of feather lice. On first year birds, every single one of them does. Look on the brown contour feathers of the back. You will see that the margins of these are quite irregular, as though they've been eaten away. They have been. The feather lice eat away the white parts, leaving a very irregular brown edge.

Then look at the same feathers on any adult. You are likely to see some irregularity, but much of the whitish margins of these feathers will be unconsumed. The adults stay ahead of the feather lice. The youngsters aren't good at it. This is often an indicator of a hawk’s general health. Those in poor health or nutrition are badly feather eaten. Survivors have the lice, but with markedly reduced damage.

And for anyone concerned that these little arthropods might have jumped off my captive birds and infested my person, don't be alarmed. These very tiny bugs are absolutely confined to buteonine hawks. They couldn't even survive on the feathers of a pigeon or robin, let alone on human hair. The feather lice of my beloved red-tails pose no danger to me or anyone else. They stay on the hawk, or die.

Sincerely,

John A. Blakeman

Sunday, February 20, 2005

My Daring Hypothesis: A Question For John Blakeman

There is a "plethora" of red-tailed hawks in Central Park and environs these days. I can't resist offering a somewhat audacious thought of my own:

Pale Male has been breeding successfully since 1995. Each of the 3 offspring of that first nest would have been ready to breed themselves by, let's say, 1998, and THOSE birds could have produced Pale Male grandkids by 2001. Then there are the three offspring of the 1996 nest, who could have each had young by 1999, and so on and so on. Meanwhile Pale Male and his mates have been producing eyasses year after year -- a total of 23 who lived to fledge.A mathematician would have to figure out how many possible Pale Male children, grandchildren, etc. there could be by now. Since it is a geometric progression, I'd bet that number is huge!

John Blakeman has previously written of the 23 offspring:"I'm certain that the majority died in their first summer." That was written on Dec.26., almost 2 months ago.[For this and other references to past Blakeman letters, scroll down on the LATEST NEWS page.] I wonder if his thinking has changed about this since then, as he has come to recognize that the NYC redtail explosion represents a possibly different reality than the situation he is most familiar with -- the rural and suburban redtail.

Obviously, I am not a biologist. Nevertheless I have a strong hunch -- partly stimulated by the timing of the local proliferation of redtails, partly by the fact that so many of the local hawks are making attempts to nest on building ledges rather than trees[unsuccessfully, so far, because of absence of spikes anywhere but at 927 Fifth]-- a strong hunch, as I say, that there is a connection between Pale Male and these proliferating NYC redtails. As I wrote to John Blakeman before, how extremely odd that before PM arrived in Central Park there were NO resident redtails in Manhattan. Now they're a dime a dozen.

I'd buy the no-more-boys-in-the suburbs-shooting-redtails hypothesis John proposed in a letter on Feb. 6, 2005, except that an alternate hypothesis makes more sense to me. I'm about to propose it, knowing well that I'm going way out on a limb, and that I really am unqualified to make scientific hypotheses at all! But perhaps it will stimulate an interesting answer, so here goes.

Is it possible that Pale Male is, in fact, some sort of evolutionary breakthrough? While Blakeman has written about the intelligence of hawks as compared to the Corvids or parrot families, [that is, that hawks are not the sharpest crayons in the avian box] perhaps Pale Male is actually a smarter redtail?

He has succeeded at building and maintaining for 11 years a pretty unique nest. He has managed for all that time not to eat a poisoned rat or pigeon, nor to collide with a truck on the highway, nor to fall prey to any of the various slings and arrows of outrageous fortune that others of his kind run into.

Maybe he has passed on this gene to a bunch of others who are managing to survive that perilous first year better than redtails did before, discovering new prey sources, perhaps. [Blakeman has speculated earlier, in a letter not posted, that pigeons might be an important factor here]. Anyhow, I've run this idea up the flagpole. Long may it wave.





Lincoln Karim
Pale Male with sprig of evergreen in bottom photo
[(See Blakeman comment below]Marie,

The intelligent question was asked [by Karen Anne Kolling], “What do they line the nest with?” As the nest approaches full structural size, lining will be an important next step.

Right now, the nest is almost surely just a moderately intertwined pile of sticks. But this would not be able to retain the heat needed to incubate the eggs. Many first-time red-tail nests fail to get properly lined, and cool March winds blow right through the structures. Needless to say, the eggs laid in these insufficient nests fail to hatch. I've seen this quite often, frequently in marginal habitats, almost surely by newly-mated pairs that haven't learned yet how to properly prepare a successful nest. Pale Male’s first efforts may have been of this nature.

The nest lining has to be wind-tight. When watching either of the pair settle down on to the eggs to incubate, notice the deliberate manner in which this is done. What you can't see is that as the bird gently wiggles down onto the eggs, the parent is putting the naked skin of its abdomen right on to the eggs themselves. These bare patches can't be seen when the birds are flying, as they are under the outer body feathers. But before incubation the inner down feathers of the abdomen are lost, creating the “brood patch.” The brood patch seems to be larger on females than males.

So, while the birds are sitting on eggs, the adult’s body warmth is being transmitted directly into the egg. If the lining of the nest isn't tight, too much of that heat escapes and the embryo or unhatched chick (it’s not an eyass until it hatches) won't develop properly.

What, then, is the lining made of? It varies greatly, depending on what the birds have available. It’s usually some light, fluffy, fibrous plant material. The thin flakings of wild grape vine is used, as is the light, shedding bark of smaller dead tree limbs, providing little sheets of paper-like material that can be pressed together in the nest. Out here in rural Ohio, last season’s dead corn leaves are commonly used.

The birds will simply look for whatever is locally available. Most importantly, the material must be able to be tucked and compressed. Clumps of dead grass stems are often used. A fist-full of partially decayed (but dry) leaves works. It would be interesting to document the preferred lining materials of Pale Male and Lola. What does the vegetation of Central Park have to offer?

If they haven't yet, some time soon the pair is likely to start bringing sprigs of evergreens to the nest. No one has ever figured out exactly why this is done. A well-needled tip of a pine branch is brought to the nest and either tucked into it on the side, or sometimes arranged at the edge of the rim. The birds have a strong compulsion to do this, and out here in rural northern Ohio where evergreens of any sort are uncommon, we know that some birds have to fly several miles to find a valued pine or spruce tree. The best explanation is that the evergreen sprigs tend to repel feather lice and other invertebrate vermin – except that eyasses in their first weeks often are pestered by a number of bugs nonetheless. The green-sprigs-at-the-nest story is still an unexplained one.

This is an experienced, successful pair. They aren't doing anything new that they haven't done so very successfully before. Getting the apartment ready for the new brood of eyasses becomes important once again. Watch to see when lining material begins to appear at the nestsite. That’s rather equivalent to the buying of the bassinet and other accoutrements that human moms do when they know that live-giving things are about to happen.

As a falconer who gets to watch my red-tails hunt and kill, where I see close at hand their remarkable power, speed, and predatory determination, to watch their markedly converse behaviors of gentleness and care at the nest is always a striking contrast. At the nest, I still find red-tails almost totally out of character. I'll have some more comments on that when incubation starts. But to watch a red-tail at the nest is a special privilege, seeing it behave in considered ways seen nowhere else.

And New Yorkers can just go to the right spot in Central Park, ask to take a peek through a spotting scope, or just look up there with a pair of binoculars to see this remarkable spectacle. Although I've seen it here in the wild many times, I'm still a bit envious. You can see it both with ease and at length. Very special. Very special.

Sincerely,

John A. Blakeman

Why are there 5 Redtails at the Azalea Pond? Isn't that Pale Male's Territory?

Marie,

You forwarded a nice note from Sally and Peter Johnson where they noted five red-tails apparently associating together, or at least tolerating each other. None of these were Pale Male and Lola. The Johnson's noted that all of these birds were "juveniles," (exactly the same term for "immatures," birds in their first year).

This is unusual, of course. (But that’s true for so much of the rest of the Central Park red-tail saga.) Here’s my take on this.

Although the 927 nest is under daily construction, it’s still deep winter. Sex hormones are starting to flow, prompting the copulation and nest building being observed. But so far, there is no impending food shortage for any of the Central Park hawks. As I so often point out, food is everything for a hawk. If food is abundant and available, territorial imperatives recede. If resident hawks perceive that ample food is close at hand, they will be rather accommodating of intruders in the fall and winter. Prime red-tail habitats, areas with lots of prey, often have large fall and winter groups of hawks. In the winter, in prime areas, red-tails can be almost social, just as the Johnson's described in their email forwarded to me.

Presently, Pale Male and Lola have access to essentially unlimited prey animals. From this, they are expressing virtually no territorial defenses. Don't for a second think that our resident pair is inadvertently unaware of each of the other red-tails in Central Park. They see every wing flap of these youngsters and keep track of where they fly, perch, and hunt. Our experienced adults know and keep track of the entire red-tail scoreboard.

For now, the young hawks are hunting and eating in CP just like our celebrity pair. But let’s see how long this continues. All is well just now. Presently, there is a general raptorial rapprochement regarding hunting and perching venues. There is plenty to go around.

But things are likely to change significantly when Lola becomes gravid, when her first egg begins to form. Egg formation requires a large amount of calcium, proteins and lipids, which are all absorbed from the mother’s body tissues. Very quickly, the female’s outlook on life changes. I've watched this in the female red-tail in my captive breeding trials. When eggs begin to form, the female takes on a serious, even morbid attitude. Life instantly gets very, very serious.

Food becomes very important, and competition from interloping youngsters is likely to met with stern behavioral warnings to leave. Pale Male will perceive the new hunting and territorial regime, one that precludes un-needed competition from other nearby hawks.

The inordinate winter abundance of red-tails in Central Park is not likely to persist. For now, food is abundant. But when our resident adults begin to perceive that things could start to get tough, first to produce a pair or trio of eggs, then to help feed Lola during incubation, and finally, when eyasses have to be fed for 16 hours each day, our birds are likely to become downright intolerant.

Once again, the entire CP red-tail phenomenon revolves around the abundance of prey animals. If there is lots of food, there will be lots of hawks. When food begins to become harder to procure because of competition, the adults will either drive off the interlopers, or have a reduced brood size. If five or so immature red-tails remain and compete with Pale Male and Lola, only one or two eyasses may be produced this year. At worst, none would be. It could be an empty nest year.

It’s possible that the following could occur. What happens if the five immature winter hawks simply disregard the behavioral admonishments of the adults to scram, to leave the area? Would that be possible? Could be. Booting out one or two incursive intruders is a reasonable task for an experienced resident pair. But perhaps the five youngsters perceive that the pair of old fogey adults simply can't cover enough space to keep them out. As an adult chases after one youngster, another simply flies over to the abandoned space that the adult just left. If the immatures are impudently unresponsive (unlike your kids and mine, who perfectly responded to our adult admonitions), the entire process could devolve into something of an unproductive flying circus. Do we have now a gang of juvenile delinquents that might disrupt the normal conventions of red-tale domesticity? Let’s see what happens.

Again, I've never seen anything like this in the rural wild. This is all new. Nothing is decidedly settled. And should, perchance, this year’s brood size be reduced or altogether absent, don't fret. Let’s honestly prepare ourselves for what might become a biological reality, that the annual production of three-eyass broods is unsustainable and atypical.

As long as Pale Male and Lola had no hunting and prey competition, when they were the only game in town (or the Park), everything went their way. But that may no longer be the case. The rats and pigeon prey base may now have to be divided with, or shared among, some other Central Park hawks. At some point, a CP red-tail saturation point must be reached. Originally, I would have projected that a single pair exploiting the entire Park was saturation. I was wrong. There have been as many as three Central Park resident pairs in recent years, and now there are the added winter immature population. (After all, this is New York City. Residents of every species live closely packed together in high density.)

Let’s watch what develops. I'm betting that the intruding youngsters will be driven out and few or none will be seen in March and April. But a quite alternate scenario might develop, with unexpected, even untoward results for our pair.

And most of us just thought we were merely watching the uneventful lives of a single pair of red-tailed hawks. Nature is seldom so neat and tidy. Things in the wild are usually a continuing interplay of multiple forces and factors, just as are being seen with Pale Male and Lola. Isn't this as good as the plot of a great novel, the thematic development of a great symphony, or a walk through a great art exhibition?

Sincerely,

John A. Blakeman