This year’s clutch was completed with the laying of a fourth egg just after 3 a.m. on 1st April. The birds have, therefore, been incubating for a little over two weeks and they are well into their usual routine. The female incubates throughout the night and the male takes over for an hour or two early in the day. He usually returns to do another shift – often lasting 2 to 4 hours – in the afternoon.
Peregrines begin incubation with the laying of the penultimate egg, which was on Wednesday, 29th March. Last year, the first hatching was 34 days after the laying of the third egg. Using this as a guide, I would expect the first hatching this year to be on Tuesday, 2nd May. Factors such as the outside temperature can affect incubation time, so this date is only a guide and hatching could begin a day or two either side of this date.
The first three eggs should hatch very close to each other and the fourth egg should hatch a couple of days later.