30 April

We had blustery winds and pelting rain all day yesterday, last night, and early this morning. In the midst of this tumult, snug under Bell's feathers and warmed by her brood patches, two tiny eyasses broke out of their shells. Our video tape review confirmed the first hatch late last night at 2334; the second hatch was approximately 0339 this morning. We expect the remaining two eggs to hatch either later today or tomorrow, so look for further updates...

27 April

The end of incubation is in sight, and soon we should have chicks. Bell laid her first egg on 3/21 at 2336, the second on 3/24 at 0506, the third on 3/26 at 0724, and the fourth and final egg on 3/28 at 1314. Incubation usually starts with the third egg and lasts about 32 - 35 days. Last year, the chicks hatched on 5/2 and 5/3; this year, since she laid a little earlier, we expect hatching somewhere between 4/29 and 5/2. Embryos require heat to develop. Incubation transfers heat to the eggs, through contact between the eggs and the adults' brood patches. During the first half of incubation, the embryo is more or less free-floating in the shell. When the adults turn the eggs, this prevents the embryo sticking to the inside of the shell. If it did, its life support system within the shell would not form completely, and the embryo would eventually die. During the second half of incubation, the embryo becomes fixed within the shell as it moves into position for hatching. So, although incubation is tedious to observers, there's a lot going on inside those beautifully marked eggs.

3 April

Bell laid four eggs between 3/22 and 3/28 (we will provide specific times in a later "Field Notes" update), and now both birds are attending to incubation duties. Although Stewart, as usual, began covering the eggs almost as soon as the first one was laid, Bell has done the vast majority of incubation since laying her third egg. Females normally incubate more than males, but the first week of incubation has been more lopsided than usual for this pair. This may be because of the cold, windy, and wet weather that we've had for the last couple of weeks. While Bell and Stewart have a well-drained nest box, many peregrines nesting on cliff ledges are not so lucky and will have nest failures because of chilled eggs resting in water.
It will be interesting to see how Bell and Stewart split incubation duties as the season progresses. Last year, they split incubation roughly 55/45, Bell/Stewart. Prior years have ranged from 60/40 to 80/20. Meanwhile, she's spending a lot of time on the eggs, and he has lots of time to hunt for her and for himself.