Tuesday, May 09, 2006

Trump Parc update and Blakeman answer to reader's question

Pale Male Junior soaring over Central Park South - 5/6/06
Photo by Lincoln Karim

This dispatch just in from our informant whose window looks directly down into Junior and Charlotte's nest

Just to bring you up to date, the female is still on the nest, and she is sitting on one egg.
Nothing new.

Next, a related question from website reader Paul Pollets :

Hi Marie,

I was wondering if there are ever cases when RT hawks will lay another set of eggs in the same season, if the first set doesn’t hatch?

As usual I forwarded it to John Blakeman in Ohio. Here is his response:

Good question. I'm sure red-tails are able to do this. In captive breeding of almost all raptors, including the Buteos (which includes the red-tails), initial clutches of eggs can be removed just before hatching and if sufficient food is available, a new clutch is often laid. So yes, a second clutch can be laid.
But sadly, it probably won't be. I've never seen this in a wild nest, except for what happened last year with the Trump Parc pair, where apparently the nest fell apart and an egg or two rolled out and died. That was equivalent to deliberate egg removal, prompting the laying of a new clutch.
It appears that unhatched eggs are still present in both Central Park nests, so the females dutifully continue to incubate. As I noted before, the parents don't count days till hatching. Only humans do that. Hawks can't count days. They only discern increasing day lengths, which prompts them to sit on eggs. They merely wait until the eggs hatch, and if they don't, they continue to sit until the days aren't getting much longer. That changes their hormones and they finally give up on incubating. By then, usually sometime in May at the New York or Ohio latitude, they just give up on incubating and resume the normal life activities of hunting and killing food.
So the chances for a second clutch being laid at either Central Park nest is now highly remote. Unless the existing eggs would be removed, the parents will have no physiologic or behavioral prompts to begin everything all over again. It's getting very late in the season. Copulation is either rare or completely abandoned by now.
The only positive factor would be the great availability of food for the red-tails in Central Park. When food is limited, egg laying is reduced. Where prey is hard to find, red-tails often hatch or raise only a single eyass. With more food, two are typical. Three eggs or eyasses are produced only in territories that have abundant prey animals (along with experienced adults able to consistently kill the available prey -- as we've seen in Central Park).
Again, I've never seen a wild red-tail pair recycle and lay or rear a second clutch of eggs this late in the season. It's now too late in the season for this to happen with any certainty.
--John A. Blakeman