Friday, May 18, 2007

My previous letters to DEC and their replies

On 5/10/2007 4:33 PM I wrote Barbara Loucks and Chris Nadareski of the DEC:
Dear Barbara and Chris,

I understand from a conversation with Ward Stone two days ago
that you have agreed to undertake the removal of this years's eggs from
the nest at 927 Fifth Avenue. I'm writing to assure you that this idea
has the complete support of the Central Park hawkwatching community.
I've also spoken to Ygal Gelb at NYCAudubon, and know that they too,
are eager to have this happen.

Based on hawkwatchers' records, incubation began this year on
March 11th. That's the day Lola began spending nights on the nest and
when exchanges began. But even assuming that this is not a precise
date, and incubation began a week later, there is no chance that the
eggs will still hatch. Meanwhile, we are afraid that there is a chance
that if the eggs are not retrieved soon they might again prove to be
too decayed to provide answers to our questions about the causes of the
three-year nest failure. .

The fact that Pale Male is fifteen years old certainly makes it
possible that his fertility has been the major factor in the nest
failure. I know there are people convinced that this is the case.
Nevertheless, the nest's success until precisely the moment the new
structure was put up on the 12th floor ledge, though perhaps completely
coincidental, does raise questions and does require that doubts about
fertility be once and for all resolved. This, of course, will be easy
to accomplish if the eggs are retrieved and the egg material is
microscopically analyzed before it is too decayed.

Meanwhile, let me mention that I and the Central Park community
understand that
retrieving the eggs with the redtail pair still in residence will not be an easy job. Please don't think that we take
your willingness to undertake it lightly. We are relieved and grateful
that you are willing and able to retrieve the eggs. This letter is only
to encourage you to do it as soon as possible so that it will not, once
again, leave us without conclusive answers to our questions.

Yours most sincerely,

Marie Winn

PS In regard to the fertility question, I might also mention that last
year I spoke at length
about redtail fertility with Ward Stone, Len Soucy, and Cal Sandfort of the Peregrine Fund's Center for Birds of Prey in Boise Idaho . I found that all three felt somewhat doubtful that a 13- or 14-year-old red-tailed hawk would prove to be infertile
after being
seen that year copulating with undiminished vigor and frequency,
especially when these observers could compare his behavior with that of
previous, successful years.

After weeks of waiting this letter seemed to lead to real results. Here is Barbara Loucks' reply:
    Yes, we will be collecting the eggs this Wednesday. We have a very busy day planned but will squeeze it in in the am.  

To address a few of your other comments, you imply that if the eggs are gathered quickly enough that it will be easy to accomplish that "doubts about fertility be once and for all resolved ". I have to disagree. All it will tell us is the condition of these eggs. We may never know why they have failed the last few years, just as we generally don't know why other raptor nests fail in the wild.

While we may be curious, and would love to know, and are disappointed when young are not produced, there may never be "conclusive answers" about this particular situation. If a new, younger male were to show up or a new female, and they were immediately successful, that might lead one to draw conclusions (that may or may not be correct). If these eggs once again contain no embryos, we can also speculate. Since Pale Male isn't banded, he could be older than 15, even much older.

I would also disagree with your comments concerning frequency and vigor of copulation indicating fertil
ity. It does not guarantee successful fertilization /hatching. From the pictures I have seen on the web this spring, I think the nest looks good again, a lot of sticks. We'll let you know what we find.

I replied to that letter as follows:

Thanks for your answer. I appreciate your time and patience here. Three more points:

1. We do know how old Pale Male is quite exactly, because when he was first seen in Central Park in 1991 he was a browntail. [Hawk experts have noted the uncommon though not unprecedented fact that he bonded with a female and built a nest before he gained adulthood.] According to Ward, it is likely that his first two nests on Fifth Avenue [1993 & 1994] failed because of immaturity. [Ward analyzed decaying egg material from PM's 1994 nest. His report was the same as in 2006 -- no embryonic material visible] Pale Male's third breeding attempt, in 1995, yielded two chicks. Every subsequent nesting year was successful [total = 23 chicks] until the year after the nest was removed--2005.]

2. I was given to understand by Cal Sandfort and by Ward Stone that a simple test of the egg material will reveal unequivocally whether the egg was fertilized. [I'll include a copy of a paragraph from my interview with Dr. Sandfort at the end of this note.] A microscope study will reveal only haploid cells if the egg was unfertilized. The presence of diploid cells indicates fertilization, whether there is any embryonic material visible or not. If the eggs were fertilized and then chilled in the earliest stages, for example, there would be no visible traces of embryonic material. But there would be diploid cells to be seen under a microscope. I understand that once the eggs are in an advanced state of decay, however, this test becomes difficult if not impossible to accomplish. This is why speed is of an essence now.

3. Re "the nest looks good" :The problem may not be the actual "cradle" structure. It may be a combination of the cradle and the anti-pigeon spikes that were included inside the cradle. The spikes were critically important when they were the only thing anchoring the sticks to the ledge. When the nest was removed once before, in 1993, the spikes were left in place, and the hawks easily rebuilt the nest in 1994. But in 2004 the spikes included in the cradle may have been anti-productive, either by impeding egg rotation, or by somehow conducting cold to the eggs. In retrospect
it might have been better not to include them. The cradle now was sufficient to contain the sticks. Of course I remember well that the hawkwatchers were fixated on the importance of the spikes -- being shocked when they were removed along with the nest in December 2004. Everybody then wanted the spikes included in the cradle. And of course I know this is all speculative. would simplify everything if we could establish whether the eggs were fertilized or not. For if they were NOT, there we have a very simple answer for why the nest has been failing for the last three years..

From 2006 interview with Dr. Cal Sandfort of The Peregrine Fund's Center for Birds of Prey, Boise, Idaho

C.S. "If the embryo died between 1 and 4 days after it was laid, if you opened it up you wouldn't be able to see anything. There wouldn't be enough embryonic tissue, blood vessels and so forth to amount to anything you could see visually."

M.W.: Well,, could you still find out about those 1-4 days is some way?

"Yes, there's a stain. ... you can stain the blastodisk -- the initial embryonic material -- the way you stain bacteria on slides, and in that way you can determine fertility even before you have very much embryonic development. An infertile egg does not stain. There's no blastodisk there to stain"

Here is another viewpoint, from a biologist [John Blakeman] I've been corresponding with.

Unfortunately, the study of the retrieved eggs last year [2006], as I understand it, was only able to do a gross anatomical examination, no cellular or tissue studies. This did not determine the "ploidy" of the eggs. If the cells were diploid, they would have had a complete, double set of chromosomes, half from Pale Male and Half from Lola. If the cells were haploid, having chromosomes from only Lola, they would have been definitive evidence of Pale Male's impotence.

I'm not convinced that the lack of gross embryonic structures in last year's eggs indicated haploidy, non-fertilization. The eggs sat on the nest un-refrigerated for weeks before being retrieved. The delicate embryonic tissues could have enzymatically degraded, even without bacterial contamination. There are biochemical tests that could have been used to determine the former presence of an embryo. If the eggs were cooled from the start of incubation, the microscopic embryo would have never developed and couldn't be seen upon gross examination.
He added:

Other than staining the blastodisk, another way may involve DNA analysis. After things have degraded, this may be the only way to do this.

PS to Barbara from Marie -- I know DNA analysis and perhaps other methods of microscopic analysis may be expensive. I believe there are funds available, from interested Pale Male fans, to cover these expenses.

Dear readers -- that's the correspondence. You have my latest letter and Loucks' final answer on the preceding post. I don't think there's anything else I can do.