Tuesday, April 18, 2006

Is Pale Male's age a problem? Blakeman responds

Pale Male is at least 15 years old. How do we know? Because when he was first seen in Central Park in the winter of 1991 he was an immature hawk; his tail had not turned red. He could have been no older than two years old that winter.

Fifteen is not young in redtail years. Though there are records of individual Red-tailed Hawks living past 30, the average life span of the species is under five years. So could it be that Pale Male is too old now? Is that why the eggs are not hatching? [Hope is not gone, but it is slowly beginning to fade.]

I sent the question to John Blakeman. Here is his reply:

Pale Male too old? Nope, I don't think so. He's in his mid to late teens, isn't he? Many falconers' red-tails are several years older and still hunt with skill and alacrity. Many captive red-tails (if they aren't overfed, which most captive, non-falconry red-tails are) live well into their late teens and early twenties.
Pale Male is still flying around Central Park and hunting with absolutely no visible reduction in his skills. How could I know this, without ever having been to NYC or Central Park? When Pale Male begins to fade, everyone who knows and has seen him in action in CP will recognize his diminished powers.
The first thing he would give up would be nest building and the tending of his mate. If he were reduced in any survival capacities, he'd stop expending any energies for his mate and concentrate solely on hunting and feeding for himself. He's continuing to hunt and nest- and mate-tend as before. He's not worn out.
Come on. How many times was Pale Male seen in otherwise compromising behaviors this year? Pale Male still has it -- and Lola, I'm sure, got it. He may be a bit white-headed, but when Lola gave the signal, he responded.
Of course, Pale Male's reign will eventually come to an end, some years in the future we all hope. What then? In the wild, a "floater," a circulating new young adult looking for a mate is likely to jump right in and fill the reproductive void. In the wild, pairs that lose a mate can find a new suitor at the edge of the territory sometimes within hours of the death of a local resident. Within a day or so it can take up the duties of the fallen hawk.
So I'm not so concerned that the loss of Pale Male will be the loss of the 927 red-tailed hawk nestings. This might be a problem only if both birds were to succumb at the same time, leaving an entire territory vacant, with no surviving bird to lure in a new mate.
And of course, upon the appearance of a new breeding mate, the question will arise of its ancestry. Would or could the new breeder, the new mate, be an offspring of Pale Male? Yes it could, but we biologists would much prefer a new, totally unrelated bird, to reduce inbreeding problems.
But let's wait for those problems to arise. For another year, Pale Male is with us doing his noble things. Let's revel. The future will take care of itself nicely. Nature makes its provisions.

John A. Blakeman
I wanted to be sure I understoo0d Blakeman's answer, so I wrote back:

The issue here is fertility, not hunting skill. Could one assume the two go together? Any data anywhere about male hawk fertility and whether it diminishes with age?

Blakeman replied:

Yes, hunting skills and fertility are directly related (in males). Spermatogenesis, the production of sperm and semen, relates directly to general health, not to age. In captive breeding programs old male hawks remain fertile usually until they begin to decline and die.
My greater concern would be the onset of other, general geriatric conditions which usually are manifested with reduced powers of flight and killing skills (arthritis and some microbial diseases). As long as these are not evident, we needn't concern ourselves with Pale Male's siring powers. He's continuing to eat well, to fly well, and has engaged in a full season of copulatory adventures with his mate. He's transferred his genes, I'm sure.
Female hawks, however, can indeed egg themselves out. Egg production is metabolically taxing. Spermatogenesis isn't. Reduced egg production at age is known in both captive breeding peregrines and Harris' hawks - but only when the birds have been "double-clutched," where fertile eggs are removed after being laid to induce additional eggs. It's clear from these studies that older captive females that have numerous eggs removed can get "egged out." But I know of no evidence of males ever getting "spermed out."
Our man is entering his golden years, but in full vigor and power.
--John Blakeman