As spring turns to summer and ecologists across the land are coming to the end of Great crested newt survey season and are planning for the bat survey season, I try find some free evenings to help with my local Barn owl group. For a number of successive years I assisted the Mid-Cheshire Barn Owl Group with checking and ringing Barn owls in the south Warrington area. Members of the group hold licences from Natural England and the British Trust for Ornithology which allow them to come into close contact with these legally-protected birds.
In previous years we had selected a number of locations for Barn owls boxes, based on a number of criteria such as the number of possible nests and roosts already available, surrounding habitat and absence of human disturbance. The boxes were built and installed by the group, which consists entirely of volunteers.
An initial check of the Barn owl boxes is made in early summer. This enables us to determine which boxes are in use. If the box is inhabited then any adult owls are captured in a net and examined. The birds are weighed and measured, and the age and gender of the bird are noted along with the details of any identification rings. Birds without an identification ring are fitted with one. Whilst the adult bird is being assessed the nest box is checked for the presence of eggs. The number of eggs is recorded and a return visit to the nest is scheduled. The adult is safely returned to the box. The whole process is completed very efficiently and quickly to ensure that any distress to the birds is minimised.
A follow-up visit is undertaken to the active nests. The young birds are carefully taken from the nest and are measured to establish their age. Birds of a sufficient age and size are then fitted with an identification ring and are returned to the box.
The success of Barn owl chicks is dependent on the availability of food. Their diet consists mainly of Short-tailed field voles, and so a good vole population and good hunting conditions are essential. Wet and windy weather will affect the ability of the adult Barn owls to hunt, and so poor weather conditions in summer can have a significant effect on Barn owl numbers. In years of optimal summer weather conditions Barn owls may raise two broods.
Not all Barn owl boxes are inhabited by Barn owls. Some remain empty, in which case the Barn owl group my look to reposition or repair the box. Some boxes are found to contain other birds, with Stock doves being common occupants. Kestrels will also often use Barn owl boxes to nest.
Paul, UES Ecologist