Question: How soon will the eggs hatch?
Answer: Peregrine eggs hatch about 32 days after incubation begins(*), but it is hard for most people to tell when incubation begins in earnest.
I have tracked the “first egg” and ”first hatch” dates at the University of Pittsburgh and Gulf Tower nests for many years. Even though I should be calculating from the “incubation began” date, I’ve found that the average at both sites is 39 days from first egg to first hatch, though it varies a bit from year to year and nest to nest.
All but one of the eggs usually hatch on the same day. The last egg is younger — it was laid 40 to 60 hours after incubation began — so it hatches that many hours later.
The photo above shows hatched eggs and chicks at the University of Pittsburgh nest in 2013. The father bird, E2, is standing near the nestlings who are in a pile with the other unhatched eggs. The white fluff in the center is the first baby peregrine, already dry. The just-hatched chick is pink and wet. The scattered reddish and white bits are the discarded egg shells — outsides are red, insides are white.
When the mother peregrine is covering the chicks and eggs to keep them warm, how can you tell if any of them have hatched? The big hint is a half-eggshell, discarded away from the scrape.
For more information on incubation, read The Big Sit
For information on how the chick gets out of the egg, see How Do They Hatch?
(photo from the National Aviary webcam at University of Pittsburgh, 30 April 2008)
(*) The incubation time span used to be listed as 33-35 days. It is very hard to tell when it begins.