Two thirds, one third

With 20 days now passed since the final egg was laid, we’re about two thirds of the way through incubation.  With work on the security lighting at St George’s completed without undue disturbance of the pair they continue to sit quietly, both male and female sharing duties and barely leaving the eggs uncovered for more than a minute between them.

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There is far less calling than was the case during courtship and when the eggs were being laid, though the male did call quietly to the female from the ledge round the corner when I went down at the weekend, apparently looking to encourage her off the eggs so that he could take over.  A little later she was on the high-level lights on the E side, where both adults are spending a fair amount of time, perhaps enjoying the early morning sun that falls on that side of the building, especially with the cold night-time temperatures recently.  In the picture above she has just left the light, heading off towards the city centre.

With the Peregrines generally inactive, it’s a good time to notice other breeding species around the church, with Starlings prominent as they feed on the short grass before flying up to their nests in stonework ornaments of the university buildings nearby.  

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In response to my post about the third – immature – bird that has been around on occasion, Andy D replied to say that he’d seen an immature over Sheffield in Feb-March that was to all intents and purposes still in juvenile plumage, far less advanced than the bird in my (not very good) photo.  A bit of reading up on this suggests that both stages of plumage would be possible in a bird from last year’s clutch!  There is much variation in the timing of the first moult of juveniles: some begin their first moult in the March after they hatched (so aged 10-11 months) while others may not have moulted by December (so aged 20-21 months).

And JLS notes that many species of birds feel where the eggs are in the nest when moving onto them.  Unable to see the eggs as they lie under their body, the feet may act as a good way of locating the eggs before settling down onto them in such a manner as to engage the brood patch.

Finally, a Peregrine fact to share after some extensive reading: the first British record of breeding on an occupied building dates from 1864 or 1865, when a pair reared young on Salisbury Cathedral. 

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2 comments

  1. I saw today (17/4) that the eggs were left uncovered for about 20 min at the change over. The bird sitting on the eggs (female?) suddenly looked very sharply up to the right, got up and flew off. The eggs were then left uncovered for the next 20 min before a bird (male?) arrived and settled down. This happened between 14.25 and 14.45. Hope that this was not harmful to the eggs …

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