17 May 2020
Everyone was surprised when Morela laid a second egg yesterday at the Cathedral of Learning peregrine nest and appeared to start incubation. It was a week since she laid her first egg and it’s unclear if either male, Terzo or Ecco, will assist in incubation. Are the eggs likely to hatch?
Fertile eggs will hatch if they are kept at the right temperature — constantly — for the right amount of time. Once the eggs’ temperature is raised by the skin (brood patch) of the parents laid against the shell, the embryo starts to develop into a chick. If the temperature is not constant or it does not last for the right number of days the developing embryo dies.
Delaying the start of incubation is a normal strategy for many species. Ducks, shorebirds and peregrine falcons wait to start incubation until the clutch is (nearly) complete. This is not harmful to the early eggs as long as they are kept from freezing and moisture.
However, once incubation starts it must not stop until the job is done. Uncovering the eggs for more than a few minutes, depending on outside temperature, is fatal because the developing embryo is too far along.
So when Morela appeared to incubate for several hours yesterday (see video) and then stopped overnight, the chances for her eggs dimmed.
The real test will be whether her incubation efforts are constant and whether Terzo or Ecco help her. It takes a pair of peregrines to raise a family. If no male helps incubate, the eggs won’t make it.
Read more about how eggs develop in this vintage article: Incubation Chamber.
(photos and videos from the National Aviary falconcam at Univ. of Pittsburgh)