Wednesday, May 02, 2007

About the nest failure & warbler pix

Before returning to the painful question of what went wrong at 927 Fifth, here are photos of two spring migrants, a Worm-eating Warbler and a Hooded Warbler. I saw a Hooded Warbler yesterday near the Humming Tombstone, and a Worm-eating Warbler today [8 a.m.] at Belvedere Castle.

Worm-eating Warbler
Photo by Lloyd Spitalnik [taken in April, 2006]

Hooded Warbler
Photo by David Speiser - taken 5/1/07 near Humming Tombstone

Back to the nest-failure discussion

Hello, Marie

I've been doing a bit of reading, and I was wondering if nest temperature variability could be a greater problem than actual cold. What do you & the other expert hawk observers think?

Deirdre Johnson
Youth Services Librarian, Mount Kisco Public Library

I answered:
There's always been the same temperature variability at the nest. The eggs hatched every year, from 1995 to 2004, with a total of 24 chicks fledging during that period. Every single year, year after year. After the nest was removed in December 2004, and the new "cradle" was constructed and attached to the ledge in Janary 2005, the eggs never hatched again.

The hawks diligently rebuilt the nest after the nest was removed anjd added new sticks every year, laid eggs, incubated. etc. but something prevented the eggs from hatching. I don't see how temperature variability, or any other condition that was present during the 9 successful years [extreme cold, blizzards, heavy rains etc.] could be responsible for the nest failures now. It's either that Pale Male, by amazing coincidence, suddenly stopped being fertile exactly then, though he continues to show all behavioral signs of fertility [copulation, nest building, etc.] OR there's something about that new structure that impedes egg development.

Deirdre wrote back again:
It's just that I've noticed -- with more primitive organisms, anyway -- that wide swings in temperature seem more deadly than simple cold. And I thought that such temperature swings might -- perhaps -- be happening in the new nest, because the cradle structure allows a lot of air underneath, so it probably isn't as well insulated as it used to be. I thought that might make the nest more subject to temperature variability than it was before December 2004.

PS from Marie

If you look back at some of John Blakeman's speculations about the spikes conducting cold within the "cradle", maybe they go together with Deirdre's final comment to support the case that SOMETHING about the new structure on the ledge at 927 Fifth is preventing the eggs from developing