Monday, 14 May 2007

Egg Failure

Derby's peregrines are not alone in failing to hatch all the eggs in the clutch. The peregrines in Exeter hatched only one out of three and those in Bath hatched only two out of three, so we are following a bit of a trend it seems.
Note: if you are a new visitor to the blog, be sure to scroll down and see and hear the excellent YouTube video of the chicks being fed.


Anonymous said...

what a shame the other two eggs are not likely to hatch, i was wondering what the usual outcome of unhatched eggs is? will the mother throw them out of the nest after so long or feed them to her chicks?

Project Member (Derby Museum) said...

According to the Derek Ratcliffe in "The Peregrine Falcon" 2nd edition, addled eggs are usually left and may survive after the young have gone as dried and bleached relics, kicked to one side of the eyrie, but they are often broken and trampled to pieces.
This is probably the best answer we can give at the moment - but of course we are now lucky that we can watch and see for ourselves exactly what does happen.

Sue Gaughan said...

What will happen to the falcons when the chicks have grown? Will they be allowed to stay in the Cathedral or will they (as preditors) move on? Such beautiful birds of prey - why have they nested here in the first place???

Project Member (Derby Museum) said...

The work of the parent doesn't end with fledging; they have to be taught to hunt and survive. Last years chicks weren't kicked out, as might be expected. At least one remained in the area right up until egg laying was underway. Indeed, it has been known for young from the previous year to help out feeding new chicks. If our two chicks survive we can expect them to be around at least until October or November, or into 2008.
But eventually as they approach sexual maturity they will move off to find new nest sites and partners elsewhere. Perhaps Lichfield Cathedral will be next.

Why have they nested here? Well, they came of their own volition. Pegrines traditionally nested on high mountain ledges or sea cliffs. They see the mediaeval cathedral tower as a suitable inland cliff to use for perching, roosting and now breeding. But peregrine numbers crashed in the 1950s and 1960s because of the use of DDT, which affected their ability to breed successfully.
Now a specially protected species, peregrines are recovering their numbers across Britain, and some have taken to using man-made structures like Derby's Cathedral. This is nothing new - we know of records showing peregrines were using the Cathedral 100 years ago.

Anonymous said...

More than 2 in the current webcam!

Project Member (Derby Museum) said...

Thanks to the anonymous watcher reporting a third chick had been seen.

This sounded very exciting news, but it did seem unlikely so long after the first two hatched. On checking two camera snapshots taken during a feed at 8.39pm on 15th May, we could clearly see one egg in each picture, but each was in a completely different place, even though the images were taken just a few seconds apart.
We think at this stage that what may have been seen were parts of the bodies of one or other of the now rapidly growing chicks. Had there been a third chick it almost certainly wouldn’t survive anyway as it would soon get trampled underfoot by its siblings.
There was certinaly no sign that the female was feeding another bird, hidden behind the others.
Having stuck my neck out to say no to a third chick, I'd be only too delighted to be proved wrong.