Barn owls have a stronghold in the Fens thanks to the many nesting sites provided for them by farmers and wildlife enthusiasts and the extensive grass banks and verges available for hunting small rodents. As part of their Biodiversity Action Plans (BAPs) the 34 Internal Drainage Boards (IDBs) in the Middle Level BAP Partnership have installed over 100 nest boxes suitable for barn owls in their districts. In many cases the boxes have been mounted on pumping stations while others have been installed in tree sites.
In other parts of the UK barn owl numbers declined in the past but breeding pairs in the Fens have broadly increased in recent years.
Their breeding success varies considerably from year to year, reflecting the cyclical changes in the populations of their prey which is chiefly voles, mice and shrews. The nest boxes are checked by several dedicated volunteers that have British Trust for Ornithology (BTO) licences to disturb barn owls to monitor their breeding success and ring the young owls. Ringing provides valuable information on their distribution, health and life span.
Peter Wilkinson is a licenced BTO ringer and has carried out nest box checks at a large number of sites for many years. He has produced a summary of the 2017 barn owl nesting season in the Fens. A copy can be downloaded here – The 2017 Barn Owl Breeding Season in Cambridgeshire.
In a year when small mammals are numerous barn owls will have two broods of young.
Charles Gunn, Simon Dudhill and David Garner are also licenced BTO ringers that check Middle Level nest boxes and ring the young owls.
Two young owls shortly after leaving their nest box.
Other birds also use the nest boxes including stock doves, jackdaws, tawny owls and kestrels.
Fiercer and more nocturnal than barn owls, tawny owls are early nesters. Their prey often includes young rats, which their young thrive on.
Kestrels also use the nest boxes. They prey on small items including invertebrates. Beetle wing cases are often seen in their pellets.
A brood of young kestrels. One egg has not hatched.
Photos: Cliff Carson