Sunday, June 08, 2008

More on Pale Male and Lola's eggs: Glenn Phillips's question, and John Blakeman's answer

December 7, 2004--the day Pale Male's nest was removed
Photo courtesy of

Note received from Glenn Phillips, executive director of the NYC Audubon:
Marie - I've gotten a number of comments from people who seem to think that courtship and copulation are connected in some way to fertility. EVERY scientist I've talked to - some of the most respected names in ornithology - have told me that there is no correlation. (One notable non-raptor example: vasectomized Canada Geese males will defend territory, court and copulate... But there were many similar cases - of course no one gave a vasectomy to a raptor, but known infertile males routinely courted and copulated.) I was wondering if you had some source for information that contradicts what these folks have told me.... -Glenn

My reaction to Glenn's letter is this:

The issue here is not whether infertile male hawks can still copulate. The evidence of the vasectomized hawks clearly demonstrates that there is no correlation here. In the case of Pale Male's nest failures, making this seem like the primary question is a red herring.

The issue is whether a healthy hawk who has had ten successful nest outcomes and who is showing no signs whatsoever of bad health or diminished vigor [as evidenced by normal copulation behavior] can be judged to be INFERTILE BECAUSE HE IS TOO OLD when his nesting effort fails during the 11th season.

A more important question to ask would be whether there is any evidence to show that a hawk's fertility decreases as he ages. As you'll see below, [in the note by John Blakeman] there is some evidence showing that it does not.

Meanwhile, if one major change to Pale Male's nest structure occurred at the start of that 11th season, isn't it far more likely that the failure can be attributed to that change [the stainless steel cradle] rather than to the sudden onset of age-related infertility?

This is why it is so important to retrieve the eggs and ascertain whether they were properly fertilized. Only that would set the issue to rest.

John Blakeman notes, on that subject:

Infertile birds can and do copulate. Copulation, per se, does not assure or indicate absolute fertility .Fertility depends upon the quality of the involved gametes, the eggs or sperm cells, not the presence or frequency of the sex act.

But if Pale Male’s gametes are somehow now defective or insufficient, he is likely to express other, concomitant behavioral or physiological problems. He shows none.
A seminal (good word) question asks if more aged raptors can produce ample gametes, or does gamete quality or viability decline with advanced (but otherwise healthy) age? I believe that the record from captive raptor breeding indicates that viable sperm is produced throughout a tiercel’s life, that gamete viability remains throughout life.

In the case of the 927 pair, just what are the chances that sperm viability happened to decline in the years immediately following the installation of the nest support cradle? Is it mere happenstance that sperm quality, and therefore reproduction, coincidentally terminated during the year of the cradle’s installation?

Actually, that question is moot. The only real question of significance that remains is, were this year’s eggs haploid or diploid. If haploid, [unfertilized] the reproductive future of the 927 pair can be written off. If diploid, causes for hatching failure need to be further pursued.
A definitive answer, positive or negative, will allow a more rational public nderstanding of what might be seen up there next breeding season. If the eggs are unfertilized, the only answer would be that Pale Male’s gametes aren't up to the task anymore. His reproductive years are behind him
But if the eggs were diploid, [fertilized] there can remain the hope that future hatchings and fledgings might yet occur at 927 Fifth Ave. John Blakeman