Our first chough egg was laid on April 9th. Since then four nests have been filled up with clutches of various sizes. Choughs will lay up to five eggs in a clutch, with sizes diminishing with age of the adult female.
Nest 1 started on April 12th, and now has three eggs.
Nest 2 has four eggs, laid between April 15th and 21st.
Nest 3 has four eggs, laid between April 9th and 15th.
Nest 4 is still being constructed – there may not be eggs forthcoming.
Nest 5 has has four eggs laid between April 13th and 18th.
We know that our captive choughs (and probably choughs in the wild) start incubating full-time when the third egg is laid. This delays the development of the first two eggs, so as many chicks as possible can hatch together. This means they are of similar size, and have more equal chances of survival.
Using the 18 – 19 days of incubation estimate, our first chicks should be hatching on May 3rd or 4th.