Today (Tuesday) saw the appearance of the third egg, visible to some lucky webcam viewers at around 7 this morning. Given that the second egg was laid between 8 and 11 on Saturday morning it seems that there was a gap of about 70 hours between eggs (assuming it was laid early this morning, with early mornings apparently the preferred laying time), at the upper end of what is quoted as the normal range by experts.
One study of Peregrines suggests that the longest period between eggs is noted especially between the third and fourth eggs, while incubation is quite widely considered to get under way once the penultimate egg is laid. This results in all the eggs hatching in fairly close proximity to each other and no significant difference in size between the chicks, so reducing competition and nest aggression. Could it be that this will mean that we will only have three eggs this year? Let’s hope not! Clutches of three or four eggs are the norm, with larger clutches (a maximum recorded of 7!) estimated at around half of one percent. One cause for optimism that there will be a fourth egg is that individual females tend to lay the same number of eggs in successive years, and we know that this female has had clutches of four in each of the last two years. Whatever the case, we’ll know in the next day or two, and are likely to see a lot of images like the one below for the next few weeks.
Once incubation gets under way in earnest, the period to hatching is 29-32 days, but we’ll have to wait to see if a fourth egg appears before making an estimation on hatching dates. The male will incubate, though the female will typically do the bulk of the sitting. To tell the male from the female, the smaller size of the male can be obvious, but another means of separating them is the pattern of the black hood: on the female (above) there is a clear white patch on the ‘cheek’ between the moustache and the nape, while the male has an almost entirely dark hood (below), with no obvious white ‘cheek’.
Visits to St George’s continue to produce good views of the birds, with copulation again noted on Sunday morning. The Peregrines are not the only birds breeding around the church, with Blue Tit, Mistle Thrush, Blackbird and Crow all preparing for the breeding season. The Mistle Thrush even flew up to perch on one of the church’s turrets to scold the male Peregrine, while he flew off at one point to attack a Crow.
The Crow could be considered an egg thief, but it is thought that other potential prey species may in fact benefit from nesting near to the Peregrines. While smaller birds may enjoy protection from potential predators (such as the Crow) the Peregrines in turn may benefit from the early warning of potential predators provided by the many pairs of eyes of other breeding birds. Things are likely to settle down to a pattern of one bird sitting and the other perched nearby, but there will still be much to enjoy, either via webcam or in person if you can get down to St George’s.
And with the clocks set to change next weekend, light evening are on the way! In any case, we can enjoy watching them by night, something experts like Derek Ratcliffe, who wrote the definitive study of the species, simply couldn’t do in all his hours of watching Peregrines. This is great stuff and real insights into aspects unknown until very recently. In the picture below, the female has just stood up and turned at least one of the eggs, showing that incubation is active, day and night.