Friday, July 21, 2006

Pale Male and Lola's eggs

First, a chronology for 2006:

Incubation began about March 5
Eggs should have hatched no later than April 15
Hawks finally abandon nest--May 26
Three intact eggs retrieved by Chris Nadareski ,
NY State DEC via roof of 927 Fifth --June 13
Eggs taken to DEC lab in Albany
to be examined by Ward Stone, wildlife pathologist-- June 13
I received a verbal report: They examined all three eggs and there were no signs of embryonic material --June 15
Final report received and released by New
York City Audubon --------------------------July 14

What I know and don't know about Pale Male & Lola's eggs

I received two mailings on July 14. One was a print-out of the toxicology report everyone had been waiting for. The other was the NYC Audubon press release. I posted the release on the same day I received it: July 14th [You might want to have another look at it].

I will try to copy and paste the toxicology report at the end of this posting. But in summary, I did not see anything in the actual report that was not stated in the press release. That is, there was no toxicological smoking gun found in the numerous tests the egg material was subjected to that would explain this year's nest failure..

I was eager to see a detailed report on the fertility status of the eggs. This would resolve some of the main questions. But there was no such detailed report. The Audubon press release simply repeated the same message I had heard two days after the eggs were retrieved: "The examination revealed no sign of embryonic development in the eggs."

What does this mean?

During the period between April 15 and the time the eggs were retrieved there were numerous theories proposed about the nest failure. Many of them focused on the anti-pigeon spikes that have always formed the base of the nest. Supposedly towards the end of incubation, when the egg shells begins to thin, the spikes penetrated the shell and the undeveloped chicks died.

But on June 13 Chris Nadareski, who retrieved the eggs, found that all three of them were INTACT. That took care of the prime suspect. Among the remaining theories were these:

1. Pale Male is now 15 years old. He is too old to fertilize Lola's eggs. That's why the eggs didn't hatch. They were unfertilized.

2. The eggs were fertilized, but something went wrong during incubation, perhaps chilling, which prevented the embryos from developing. This would cast suspicion on the new "cradle" structure put up in January, 2005, to allow the hawks to rebuild the nest .

***a. This could have happened at the very beginning of incubation, when there were many bitterly cold days. If that were the case, there wouldn't be much embryonic development to be seen when the eggs were examined.

***b. Or it could have happened at any time later during the incubation period, in which case there would be chick embryos in the eggs.

3. The hawks ingested some toxin, rat poison from a baited rat, for instance, or some organochlorine from a poisoned pigeon. This did not directly damage them, but it affected the egg development and could possibly be found in toxicology tests.

4. Bad weather : Too much rain, . Or some other weather factor.

5. Something else.

Theory #3 was eliminated by the toxicology tests.

Theory 2b was eliminated by the first exam, showing no visible embryonic material.

Theries 4 and 5 are essentially unaswerable. They would always be in the realm of conjecture.

But Theories 1 and 2a seem to me to be closely related. If Pale Male had not fertilized the eggs , shouldn't there be some way of testing the eggs to find out? After all, as the press release stated, the examination of the eggs done on that first day only indicated that "the eggs never passed the early stages of development." This does not answer the question of Pale Male's fertility. Nor does it eliminate the possibility that something about the "cradle" was a factor in the nest failure, perhaps by conducting cold to the eggs from the very start of incubation. That might have caused them to stop developing when the embryos were still microscopic.

My first call was to my old friend Len Soucy, the founder and head of the Raptor Trust in Millington, NJ. He's always the first call. As usual he was most helpful. "I'm not an expert on embryology," he said, but I can steer you to someone who is. He gave me the number of the Peregrine Fund's Center for Birds of Prey, in Boise Idaho, and there I was connected with Cal Sandfort, one of their biologists.

My talk with the Idaho Hawk Expert

I laid out the problem. But before he answered my specific question about a test to find out if the PM & Lola's eggs had been fertilized, he answered a few general questions about fertility in Red-tailed Hawks I think are relevant here:

When I asked if he thought a 15-year-old hawk might be too old he said "I know redtails can be long-lived. We have peregrines here that can fertilize eggs when they're 17, 18, 19 years old.

I told him that Pale Male & Lola were seen copulating many times in the late winter, and asked if there were any correlation between copulation and fertility. He said
"Generally if they're copulating and they've produced fertile eggs in the past, typically they'll produce fertile eggs until the male gets old and pooped out, so to speak."

When I asked him about the possibility that the eggs were chilled early on in incubation he answered:
"Eggs are really durable. You can darn near freeze eggs early in incubation with no problem. You can chill them almost any time during incubation--until late incubation, without much poblem. They're more susceptible to heat."

Then we moved on to the question of detecting early embryonic development in an egg.

"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."

Well, I persisted, could you still find out about those 1-4 days is some way?

"Yes, he said, there's a stain. I'll have to find the paper on this. I'm sure we have it in our library. [He hasn't sent it yet] Anyway, 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"

And then he added words that would prove to be fatal to my pursuit:

"I don't know how fresh the egg has to be in order to stain it successfully. If an egg sat around a couple of months it may not work."

I think you see clearly what's coming. I didn't want to leave you in too much suspense. Still, there's more information to come.

Tomorrow: my interview with Ward Stone, the wildlife pathologist.
and the toxicology report [if I can transfer it here]