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