Monday, May 09, 2005

Blakeman writes: our man still has it -- he's merely mature, not geriatric

An important question concerning Pale Male's age was raised:
Could Pale Male's age (around 14, I think) have anything to do with the eggs not hatching? As he is older for a red-tail hawk, will there come a time when the eggs he fertilizes are damaged in some way due to his age? I hesitated asking this question because I (and everybody else, I'm sure) don't want to think about how many years Pale Male may have left but it's been in the back of my mind. Again, thanks for sharing such a wonderful story.
Debbie Haroldsen
Debbie has raised a biologically relevant question. Aging males of most vertebrates produce sperm of reduced viability. But I doubt that this is presently a factor here. First, the pair was seen (gloriously) to copulate profusely before eggs were laid (at least before intense incubation was seen -- no views into the nest have been available). There is every reason to believe that the eggs were fertile and viable. They have been in the past, and there is no evidence that Pale Male's spermatozoa failed to successfully wiggle their ways to Lola's awaiting oocytes.
A 14- or 15-year old red-tail is merely mature, not geriatric. Pale Male continued to hunt, feed, nest-build, and conduct all of the other functions of his life with full alacrity. I see no evidence to suggest that our man doesn't have it any more. I believe there are a number of reports of birds of Pale Male's age reproducing successfully in the wild. I personally knew of a nest that was in continuous occupation (well, two nests, alternating between nearby woodlots) for over 25 years. Of course, I have no way of knowing if the a single male was the lone sire for that entire period. I doubt that one was. But nonetheless, there will likely on two or three males there, and they annually produced offspring.
When Pale Male begins to age out, I think other things will first become evident. He's likely to be less active in hormone-driven nesting behaviors in January and February. He's likely to spend most of his reduced energies merely hunting, not in breaking off twigs and carrying them to the nest. He's less likely to ascend and engage in courtship dives.
When these diminished behaviors appear, it would not be unreasonable to expect a challenge by a new, rising male, a two- or three-year old young adult looking for a prime territory and mate. With youthful testosterone concentrations driving the new bird's behaviors, Pale Male may face a challenge that he might -- someday -- elect not to defend.
It's possible that some January Pale Male will just disappear, with a new young male in his place. Our patriarch might even elect then to remain in Central Park, but take no role in mating, copulation, nesting, or brood-raising. He may retire from the duties of fatherhood and while away his remaining days merely hunting for himself.
But I wouldn't count on any of this happening soon. Our man has another three or four years, at least, I think, before age starts to slow him down. Right now, he's the High Patriarch of Central Park red-tails, with no observed diminution of his earned high repute. His spermatozoa still swim with vigor, I'm sure. Nothing else of his has diminished.
John A. Blakeman