Alongside my ringing permit issued by the BTO I also have a Natural England / BTO Schedule 1 permit for monitoring and ringing Barn Owls in a number of areas around north Wiltshire.
It has been an interesting beginning to the Barn Owl breeding season in 2023. Last year we monitored 21 Barn Owl boxes in and around the Braydon Forest. It was a pretty good year. Of those 21, we found youngsters in eight occupied by Barn Owls, three with Stock Doves and one with Jackdaws. Two of the boxes were being used as roosts by adult Barn Owls (of which we caught and ringed one). Three of the boxes had been occupied by Jackdaws that had fledged and left before our first visit. Essentially, of the 21 boxes, 15 were occupied by birds at some point and, for the reasons set out below, 13 were proven successful in fledging young, of which six were successful in producing Barn Owls.
One of the Barn Owl boxes, our most dilapidated and scheduled for removal, on first inspection did have two warm eggs and 2 small chicks in the nest. Upon next inspection one month later the entire brood had been predated. This was the first time since I started this monitoring work that I have experienced that (so our owls, and I, have clearly been lucky to date).
Over the course of the season we ringed 20 Barn Owl chicks and one adult, three each of Stock Dove and Jackdaw chicks. For the first time last year we came across some intra-brood cannibalism at two of our boxes, with the smallest (unringed) member of the brood serving as food for its siblings. This was somewhat surprising as it was such a good vole year last year that many of the boxes we checked had voles left in the box, as you can see below:
Ironically, this was one of the boxes in which intra-brood cannibalism took place. There was one horrendous end to the season when the entire brood of three ringed youngsters from one box, all three on the verge of fledging, if they hadn’t already and were using the box as a daytime roost, were found to have been predated. They were almost certainly taken by a bird of prey, given how they were found (head and chest missing, mat stripped completely but wings and legs still attached to the spine) and the fact that they had to be more than capable of flight to avoid any mammalian predator. It was the last box we checked, on the last check run of the year, and an awful way to finish what had otherwise been a successful breeding season for them.
So to this year: we have so far checked on 15 of our boxes, with another 13 to check. As you can see, we have added another seven boxes so far, with another four to be erected when we can find the time. Of the boxes checked so far we have found seven occupied by Barn Owls (two of which have held adults roosting, rather than nesting and we have ringed two adults as a result) and four with Jackdaw nests, two holding young, two already fledged. Two of the boxes had been taken over by Grey Squirrel: we cleared those out, as they aren’t being used by them for breeding.
We have already ringed two Jackdaw broods and eight young in four of the Barn Owl boxes. Interestingly, two of the Barn Owl boxes, when first checked at the end of May / beginning of June, held four chicks. When we came to ring them a few weeks later there were only two chicks in each box to ring. Again, I would suggest intra-brood cannibalism is responsible, because the remaining two chicks in each box were a good weight and very healthy. I suppose the question is: has this recent very hot weather impacted on the availability of prey or have they just succumbed to the heat?
One box we checked on Thursday evening, which had one newly hatched youngster plus four eggs at the beginning of June, had one chick large enough to ring, two chicks that are too small to ring and one cold, presumably infertile, egg. We will revisit in a couple of weeks and see how the two small ones are faring.
We will be checking on another 10 boxes next week: it will be interesting to see what we find.
Ringing In The Braydon Forest & Beyond 