Saturday, April 28, 2007

More tests for bad chemicals? The discussion continues

Donna Brown sends in a question:

Would it be possible when an examination of the eggs take place that they be tested specifically for the pesticide that is pumped into the ground in the park to save the trees?[ MW: This was for the Japanese Long-horn Beetle, a terrible threat to Central Park's hardwood trees. In fact we could lose them ALL] I understand that the chemical was applied about the time that the eggs were laid in the last two years.
I understand from Bruce that quite a number of dead squirrels were found this year during that time, therefore it was in the hawk food chain. It may have nothing to do with it but perhaps worth a shot.
Could it be affecting the viability of eggs? If it is affecting fertility we aren't likely to find anything as it would have done it's temporary or permanent damage and then likely passed through their systems.

I sent off a quick reply and then sent Donna's question on to John Blakeman. Below, my reply and then Blakeman's:

I discussed it with Ward Stone last year. He thought it was highly unlikely--they would have shown physical effects of ingesting the stuff -- and also said it was expensive to test for it and he didn't have the budget for it. Etc.. etc. Of course we could pay for the test ourselves, or get NYCAS to fund it. I somehow doubt that any amount of chemical would "un-diploid" the eggs if they'd been fertilized . But what do I know. I'll ask Blakeman what he thinks.

Blakeman replied the same day. Studying his response, I would say that I don't see a real need to do this one extra, expensive test, especially with the possibility of false positives.:

Marie and Donna,
Donna, your concerns regarding a soil-injected tree pesticide are important. But as with the tests last year for conventional egg-destroying pesticides on the retrieved eggs, I don't really think the chemicals are likely to be a factor, for several reasons. First, pesticides that easily bioaccumulate or cause secondary predator poisonings are pretty much (not always, however) prohibited.
Secondly, if the pesticide was concentrated enough to kill the egg, both Pale Male and Lola should have exhibited their own poisoned behaviors. I've seen a number of red-tails that come into one of the three raptor rehab centers in my area, and this species really looks sick after ingesting anything untoward.
Had Pale Male consumed a poisoned squirrel, he would have, as the British falconers say, "gone off," showing himself to be really down and out, plainly sick. He would have failed to hunt or eat, perhaps for as long as a week or more. Winter red-tails can easily go 5 to 7 days without food, as they sometimes must after a winter snow storm that covers the landscape and hides voles and mice.
I diligently keyed up Lincoln Karim's daily photos, and continued to be astounded at the frequency of the twig-carrying. I'm absolutely certain that this happens much more frequently with the CP hawks than with my rural ones, and it reflects, I'm certain, the abundance of food they have in the park. Twig-carrying after the nest is well along, after the hen is sitting, is usually rather infrequent. With PM, the bird was hardly seen without a twig in the beak. If he were poisoned or didn't feel well, that's the first thing he'd give up.
And I'm certain that no poison could disrupt or destroy the chromosomes. The ploidy state of the egg cells should be clear. [Marie's emphasis]
For the right price (high), an analytical chemist could certainly detect any of the pesticide in the egg, given two conditions. First, he would need a sample of the product to run through an HPLC (high performance liquid chromatography) device. From this, he'd get a typical scan or plot for the product. He'd then send some fluids from the egg through the HPLC spectrophotometer and see if it could match the scan peaks. If only a few nanomoles were present, they'd show up.
But in fact, that might be a false positive, in that the chemical was found present in the egg but in such low concentrations it may have played no part its failure. HPLC spectrophotometry is stunningly perceptive, detecting the smallest concentrations of known chemicals.
Then there's this consideration. The pesticide may have been metabolized or chemically changed after ingestion, either to a more or less active form. All of that, of course, was supposed to have been thoroughly characterized before the pesticide was approved for sale.

John A. Blakeman