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Saturday, 31 March 2012

Parliament Pair

March 27th
This morning’s visit was to confirm that they are at the alternative nest site, I knew they were from previous posts, I can also add that they are already incubating. A nest relief was seen briefly, Tiercel taking over from the Falcon with the latter returning after about 2 minutes when she found no prey stashed.Tiercels do like to incubate and he held on well as she screamed at him to come off the eggs, he grudgingly gave up his position and then flew north.
Throughout the course of the morning he really did not hunt in earnest, he even found time to copulate with the Falcon; it appeared that neither bird was in any hurry to feed, although the Falcons actions earlier belied this.


I did see rather an amusing sight, the Tiercel had departed, again north and the Falcon was incubating, into view came a Carrion Crow, he landed on the far corner of the nest site building, out of sight of the incubating Falcon but the Tiercel missed nothing. Just as I wondered how long he could stay there without the Tiercel seeing him, the Crow took off in a panic and made for some trees nearby. Into view, flat out came the Tiercel, the Crow went lower down towards the road, the Tiercel went with him, at one point he seemed to tap him, they do this quite often, eventually the Crow made the sanctuary of some lower trees.
It was quite a sight to see a Crow flying down the road at bus height with pyscho peregrine attached to his rear end, not one I will forget in a while and I have seen a few Peregrine/Crow disagreements.
Hopefully they will again succeed and fledge juveniles, a lot of people at Parliament are waiting for them to come back, hopefully it will again be early July.

On one pretty well known site in London that I monitor, the pair have not successfully bred since 2007 when they fledged 3 juveniles, before this they had been successful since 2001,blanking in 2004 and 2006.Since 2007 they go through all the motions, pair bonding, ledge display, nest site selection and copulation. Despite this and the obvious intent to breed no resulting eggs are forthcoming.
A few years ago I decided after comparing photos, that it was a new Falcon on site, the old one presumably having been usurped by this female, the problem I think lies in the fact that this Falcon may well be too old to breed, or simply infertile. I have even watched her through the telescope incubating on nothing, it was on a scrape she had made, I timed her and she was on the phantom eggs for 1 hour 40 minutes if I remember correctly, she did this on a number of occasions. I suspect it is the Falcon equivalent of a phantom pregnancy. It is something I have not heard of before regarding peregrines despite doing some research.

Falcon from the site


What surprises me is that the Tiercel has stayed loyal and has not ‘flirted’ with another passing Falcon and encouraged her in, for him to try and breed year after year with her the pair bond must be very strong. Alternatively, although old?, she may well be still strong enough to resist another Falcon. There is enough strength in depth in London nowadays that many sites are challenged daily, presumably by single birds, on one day alone on this site, I recorded 6 intruders, Falcons, Tiercels and immatures.
Alternatively I have always put it down to the Falcon, I know it is the 2nd Tiercel since 2001 but he was present in 2007 when they last succeeded, the fault I think lies with the Falcon, either age or fertility is an issue.

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