Tawny Owls and Nest Boxes
Different designs, choice of location, success in the third season
The following updates a blog written for the Woodlands.co.uk in 2018 called Owls in Boxes. It describes our various attempts at persuading Tawny Owls to nest in one of our boxes, which they do in spring 2020.
Why Owls?
What is it about the owl that is so endearing and compelling – its eyes, its face, its silent mastery of flight, or the web of myths and stories that surrounds its nocturnal life? For sure, nothing can beat staying over in a wood and hearing Tawny Owls, and even better knowing they count your wood as part of their territory.
When we were getting to know Woodcock Wood back in 2017 we heard Tawny Owls, usually some distance away, and the thought struck that a nest box might bring them nearer, and give us the chance of a view.
Nest Box Design and Location
We decided to buy a box and considered those available from Barn Owl Trust and those from the RSPB, finally settling on the one from the Barn Owl Trust because it has a larger floor area than the RSPB’s (although its plywood build subsequently caused problems – the squirrels destroyed the edges and water incursion delaminated the ply. It has since been completely rebuilt, and been given a sloping roof.)
Finding the right spot wasn’t as easy as we thought … undisturbed area, 3 to 4 metres high, clear flight path, avoiding west or southwest facing … sounds easy enough until you have to heave a heavy and bulky item into a stable position in just the right tree, but we did it. We also cleared the saplings from the ground facing the box for about 10 metres, giving the owl a clear flight path to the entrance.
Nesting Behaviour of Tawny Owls
Tawny Owls are fiercely territorial, and take anything up to 50 acres of woodland as their patch. They hunt throughout this area, and when not nesting, choose a wide variety of roosting spots. In October and November the pair spend more time together, and select their nest site.
Box and Trail Camera in Place
We had the box in place by September 2017 and put up a trail camera adjacent to the box … squirrels, squirrels, squirrels … and then early December success! Over a couple of nights an owl inspected the box.
But clearly it was not to its liking … no more owl, just more squirrels. By March the squirrels had taken it on as a project. After emptying it of twigs and squirrels several times, we blocked the entrance. It was owls or nothing!
It was disappointing not to have a resident owl in the newly installed box, but at least we enjoyed the trail camera shots of an owl exploring a potential site.
One Owlet in 2018
Our son James is a frequent visitor to the wood, and has developed a camping area under several large oaks. We were at our house in França in Portugal during May and June 2018, but he kept us updated on news from the wood. Towards the end of May he reported a lot of owl activity around his camp. From the range of calls could there be young nearby?
On 10th June there was proof. He had been climbing one of the oaks to suspend a rope and came across an owlet in the crook of the tree. Who was more surprised I’m not sure.
Looking at the tree later in the season it did appear to have been the nest site. And so, that year we had put a lot of effort into finding what we thought was the ideal site for the nest box … secluded area, fine tree, right height etc, and the owl nested in the busiest spot in the wood.
Favoured Nesting Locations of the Tawny Owl
But who encroached on whose territory? Tawny Owls generally prefer holes for nesting, but at times they nest in the open in old corvid nests, or in this case the secure crook of a tree. Such a site is more common in young woodland such as ours. We have no ancient trees or standing dead trees, and natural holes of sufficient size will be few and far between. Also, Tawny Owls tend to be traditionalists, and favour the same site year on year. In all probability owls have nested there for some years, and it was James who had moved in.
The owlet remained in the nest for two more weeks. By the 24th it had gone, probably climbing away into the upper storey of the trees – but we don’t know. Owlets are of course more vulnerable to corvid attack in the open than they would be in a nesting hole, but there was no evidence of anything untoward happening.
Spring 2019 – Where Did They Nest?
From their calls it was clear the owls were still busy around the woodland. We opened the box at the end of the summer in 2018, and the trail camera had picked up occasional pictures of them visiting, but they didn’t take to it. Where they nested, or indeed if they nested in 2019 we don’t know.
An Additional Box and Location
At some point towards the end of 2019 we bought another owl nest box to give the owls a choice of locations. This time we went for the RSPB design. The tall thin box is far easier to fix in place than the heavy cube of the Barn Owl Trust design. Rather than a secure and substantial platform in the tree, it just requires two bolts in the tree, one at the top and one at the bottom of the box. It can be positioned easily and takes a few minutes to put up. Whether this ease compromises the quality of the nest box accommodation we don’t know. The floor area in the box is about half the size of our original box, but do Tawny Owls prefer or need such a large space?
We put the box up in January recognising that it was probably too late for the 2020 nesting season, as October to November is the prime time for nest site selection. We left a trail camera focussed on the box, and went off to Portugal in February for our routine early trip of the year.
We returned at the end of February before lockdown. The trail camera showed there had been a little interest from the owls, but didn’t reveal much activity. We had a strong suspicion that the camera was operating at the limit of its range and was not being triggered reliably. This proved to be correct. At the beginning of May we checked the box for squirrel activity and there were two well developed owlets playing dead, until one blinked and gave the game away!
Four days later we returned to find a fine owlet sitting in a nearby tree. It remained nearly motionless for the hour or two that we watched. At about 5.00 pm we returned to see the second owlet sitting in the entrance of the box. It seems unlikely the first had returned to the box, because, at this stage in their development they are not flying but climbing, and such a climb would have been challenging to say the least.
A week later we checked the box, and it was empty.
Nest Box Design
A lot of factors determine where the Tawny Owl will nest. The design of the box and its floor area may seem important to us, but within reason, may be the least important to the owl.
Location and Choice of Site
To increase the likelihood of the Tawny Owls continuing to nest in this location, we recently moved the old box close the new one, giving them a choice of site. Within 24 hours our trail camera recorded two Tawny Owls checking out the new box. twice.
Influence of Squirrels on Nest Site Choice
It’s not clear from the literature exactly how much of an influence grey squirrel activity around nesting sites has on the Tawny Owl. Certainly the squirrels were extremely keen to occupy the original box, and even when we blocked the hole, they continued to spend a lot of time on and around it.
Initially squirrels seemed to be less active around the new site. But within a week or two of the owlets fledging, the nest box was full of twigs and leaves, and so it hadn’t taken the squirrels long to lay claim to it.
We cleaned out box, and so far it has remained empty. However, the trail cameras show that the squirrels regularly explore the box and its surround.
As a way of pre-empting another takeover, we have now put up a third large box in place, just for squirrels. We will leave this fine construction (indeed, too fine for squirrels, but there we go!) undisturbed, and hopefully this will reduce the chances squirrels taking over the owls’ nest boxes.
See also for the story and video of the 2022 breeding season, and more on squirrels as competitors: