Mar 19 2009
Question: Sitting on Eggs – or Not
Question: After the mother peregrine has laid an egg, why doesn’t she sit on it all the time?
Answer: Peregrines usually lay 3-5 eggs per clutch but they don’t begin incubation (to raise the eggs’ temperature) until they’ve laid their next-to-last egg. The mother bird makes sure the eggs don’t get wet or freeze but otherwise delays development of the first eggs until her clutch is nearly complete. For more information, see my blog at: http://www.wqed.org/birdblog/2008/03/16/why-isnt-she-sitting-on-the-eggs/
(photo from National Aviary falconcam at Gulf Tower, Pittsburgh, 18 March 2009)
How long before the eggs hatch on the Gulf Tower?
The earliest the eggs will begin hatching is probably May 10 — if then. This year, because of the changeover in resident females (Tasha replaced by Dori), the eggs weren’t incubated consistently at first. This means they might hatch sequentially days apart from each other. We just don’t know.
See this blog from March 30 regarding the inconsistent incubation episodes:
http://www.wqed.org/birdblog/2010/03/30/whats-happening-at-the-gulf-tower/