The James Hutton Institute is a LEAF Innovation Centre that is committed to promoting and developing Integrated Farm Management at their sites in Scotland. Euan Caldwell is Head of Farms, Field and Glasshouse Facilities and here he tells us a bit more about the bats and owls that have taken up residence at the Balruddery Site near Perth.
Here at Balruddery we installed a number of bat boxes in 2009 as mitigation for the lost bat roosts in the old byre (the old stone steading at Balruddery was knocked down in 2009). Originally 20 boxes were installed – 5 each of four types. We lost one last winter when it was blown down and destroyed. Last year we moved three boxes to the gully near Balruddery Den – these were ones which had never been used in their original locations.
The bat boxes are checked twice annually by David Dodd from David Dodds Associated who is licensed to do so. David checks the boxes to try to identify droppings to establish whether the boxes are in use and clear them of any debris: droppings, old birds’ nests etc. so that the boxes remain usable. To date we have found both Common and Soprano Pipistrelle bats in the boxes. The byre was also used by a shyer species: Natterer’s Bats and I’m hopeful they may move into the boxes eventually.
The boxes are usually used through the summer by individual male bats, waiting for the autumn breeding season. The females spend the summer in large maternity groups, rearing their young. In the autumn the males set up territories around small roosts and call females, gathering a “harem” of females. We often find these groups in the boxes in autumn. Last autumn there was evidence of a lot of activity in one of the boxes and David suggested it may have been used as a maternity roost, though it’s hard to be sure.
The Tawny Owl is one of bats’ main predators and is capable of taking one in flight in complete darkness. We have had Tawny Owls nesting for the last three years at Balruddery Farm in a nest box we put up ourselves on the eastern fringes of the farm. In years one and two there were two owlets and it was very entertaining to watch them “branch” at dusk, a term used to describe their early attempts at using their wings (jumping from branch to branch) and being fed by the adults who could be seen roosting in a nearby tree during the day.
This year there was only one owlet who was particularly adventurous! Owlets regularly fall / glide out of their trees during the “branching” stage but they usually manage quite easily to clamber back up into the tree and I have seen this happen several times. However, as this year’s baby was an only child, it seemed to have no incentive to return to the same tree it started from and I struggled to keep up with its movements. I became very familiar with the little squeaks that it made as dusk approached and found it in random trees, in a hedge row, crouching on top of a dyke and once on the main road! But I lost track of it before it properly fledged. It was well attended by the parents and was well fed. It grew at a faster rate than the owlets from previous years and I have no doubt that it made it to adult hood
Our Owls are very entertaining to watch but their presence is also a healthy sign that the habitats we have helped to create, our hedge rows, field margins and beetle banks are sustaining a healthy and productive food chain that enables a top predator like a Tawny Owl to make its home at Balruddery.