Question: How soon will the eggs hatch?
Answer: Peregrine eggs hatch “about a month” after incubation begins. However it is hard for most people to tell when incubation begins in earnest and there are many ways to guess the hatch date.
Calculating hatch date from the start of incubation … but when does incubation begin?
- Incubation is said to begin after the next-to-last egg is laid or on the day before the last egg is laid. This is a 24-48 hour variance.
- Incubation lasts about a month but is described as 30 days or 33 days or 29-32 days or 29-33 days.
- From 2009-2013 I tracked Dorothy’s “next-to-last egg” and “first hatch date” at the Cathedral of Learning in order to calculate incubation duration. She averaged 33.7 days.
Calculating hatch date from first egg date.
- In Virginia, DWR calculates that first-egg-to-hatch-date for the Richmond falcons is 38 days.
- Dorothy’s “first egg” to “hatch date” was 38.7 days (normalized to 4-egg clutches) or 39.7 days (including her 5-egg clutches).
Hatch Day: We speak of hatching as a “day” because 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)