In-breeding appears to be not that uncommon in peregrines. Tina Callender (one of our cam watchers) sent me some details of some studies in the UK strongly suggesting siblings helping to raise another brood, and later mating with his mother. BBC – Nature UK: Peregrines are keeping it in the family…
And in the states, it has been demonstrated that some 4% of the peregrine population are closely related. This often leads to a problem in populations, abnormalities etc. but apparently not (at least, not yet) in peregrines.
I don’t know of any similar studies in Australia, but will endeavour to find out. Not much in HANZAB (Handbook of Australian, New Zealand & Antarctic Birds), although I did read that fledged young have been known to reside in parental territory (less used parts) for up to nine months. This bird intruder is clearly more than nine months’ old, however. Juveniles get their adult plumage by the end of their second year.
It’s going to be interesting to see what happens when the chicks emerge in about a week. Will this new bird, relative or not, be helpful? If you listen to the audio on this video (mp4), you can hear some peregrine carry-on just before TG appears and I’m wondering if this is a very early morning spat with Xavier. It has been noticed that he has brought in less food (although today he managed what I think was a small white pigeon) and that could be a problem if he starts interfering with their routine. Hungry mouths need more than one feed a day.
Have a lovely weekend. Cilla