Barn owl by Gary Cox
The ghostly silhouette of a barn owl, seen silently floating over a meadow, marsh or field margin is a view of Suffolk’s landscape that many people treasure. But with the loss of habitat and nesting opportunities the breeding population had fallen below 100 breeding pairs in the county by 2005.
Working alongside the Suffolk Ornithologists Group, Suffolk Wildlife Trust has been involved with a countywide initiative to install barn owl nest boxes for several years now. It has helped restore the number of barn owls to levels not seen since the 1930s. The following information and contacts are designed to help you understand and manage barn owl habitat to ensure the continued success of this evocative bird.
From around 1945 barn owl numbers across the UK plummeted, with populations falling by almost 70% over 50-60 years. By the turn of the century, there were thought to be only 100-125 pairs in the county, mainly in north east Suffolk. It’s believed the dramatic decline of what was considered to be a common and well-distributed owl was caused by a combination of habitat loss and a shortage of viable nest sites.
With the outbreak of war came the intensification of farming techniques. Changes to the management of field margins, watercourses, hedgerows, woodland edges and even roadside verges meant that rank grassland - the owls’ favoured hunting site for voles, mice and shrews – became fragmented. It is estimated that since 1939 a hefty 96% of Suffolk's unimproved grassland has been lost.
A reduction in farmyard foraging by rodents due to improvements in the methods of handling grain and the lethal effects of organochlorine pesticides also took their toll. As food sources dwindled and hunting grounds shrunk, traditional nesting sites vanished as the number of hollow trees available were reduced by Dutch elm disease and other causes and barns were sealed up, replaced with modern structures or converted into dwellings.
The construction of major new road networks also hit owls hard. Not only did new highways fragment habitat, but faster traffic left owls flying at hunting height unable to avoid collisions.
Barn owl is predominately sedentary and site faithful – the same pair will use the same location year after year. With soft unwater-proofed feathers, which quickly become saturated in the rain, barn owl need sheltered nest sites, and roost sites for the male, to breed successfully. As one of the UK’s driest counties, Suffolk is a natural stronghold.
Although the owls have been severely affected by the loss of mature trees and agricultural buildings, fortunately barn owls take readily to nest boxes and since 2006, Suffolk Wildlife Trust has helped transform the fortunes of barn owl in Suffolk, through an intensive nest box programme.
Supported by a network of trained volunteers, the Trust is now monitoring more than 1,500 barn owl boxes and barn owl have spread from their stronghold in north east Suffolk into central and western Suffolk.
As a result barn owls are now seen in places where they have been missing for generations. According to a recent survey, the numbers of breeding pairs has quadrupled in four years – going from 108 breeding pairs in 2007 to 427 in 2012.
The nest box programme continues and in time the Trust aims to link up Suffolk’s barn owls to the populations on the Cambridgeshire borders.
Feeding opportunities and the availability of good hunting habitat are also critical to the barn owls’ survival and in siting nest boxes the Trust assesses the quality of the habitat and advises landowners and community groups on grassland management to ensure the box will be viable.
Suffolk’s open grassland habitats of meadows, marshes and the widespread adoption of grassy headlands on farms provide ideal hunting areas. Grassland needs to be rough, thick and tussocky with a deep litter layer to attract small mammal prey such as the short-tailed vole. This habitat allows barn owl to survive and breed as a typical family needs to eat around 10,000 vole sized small mammals every year in order to thrive.
Community sites could be village greens, community woodlands, village halls, churchyards, school grounds, and other community green spaces or buildings which overlook barn owl habitat. Good habitat for barn owls to hunt are open grassland, marsh, meadow, river corridors or arable field margins.
It is important that the habitat where the nest box is located is free of obstructions. Barn owls characteristically fly low to the ground, and their path into a nest box will be swooping ‘up and into’ the nest box entrance hole.
If you already have a barn owl nest box, please contact us 01473 890089, so that we can include you in our barn owl monitoring scheme. Pairs of boxes can relieve competition for nest sites with other species, with a second box acting as a male barn owl crash pad – once chicks hatch the female won't allow him into the box, except to deliver food. However, boxes should not be cited closer than 200m from one another.
Roads are by far the largest cause of barn owl mortality with accidents on minor roads killing young barn owls after they have fledged and major roads killing adult birds that survived fledging and dispersal. Whilst this can be partially remedied by growing tall hedges as a boundary between busy roads and barn owl hunting habitat, it is difficult to completely block off roads to barn owls because of the practicalities of having gaps in the hedge such as gateways where barn owls will naturally swoop low through.
The primary consideration when siting a barn owl nest box is whether the fledgling and hunting barn owls will be safe from road traffic. It is best to avoid siting a barn owl nest box overlooking a road as the barn owl will swoop low over the road to fly too and from the nest box. The risk of mortality in mature birds can be reduced by avoiding siting a barn owl nest box within one kilometre of a motorway or dual carriageway.
Nest box design
A poorly designed barn owl nest box will cause the death of barn owl chicks before they are ready to fledge – largely due to the chicks falling out of the nest box. If a barn owl chick falls to the ground the adult barn owls will not feed it here and it will die of cold or starvation.
The chicks usually fall out of nest boxes because the positioning of the entrance hole is too low resulting in barn owls being pushed by siblings or falling out of the nest box before they are actually ready to fledge.
This common problem can be simply solved by ensuring that the nest box is of a deep design with the entrance hole in the top of the nest box with a landing platform outside the entrance hole.
This ensures that chicks only leave the box when they are ready and able to do so and the landing platform on the outside of the box helps fledglings to gain their flying skills by practicing flying to and from the nest box.
If you would like advice on managing your land to benefit barn owls, please ring 01473 890089. If you would like to install a barn owl box on your land, you can either build your own box or buy a box. Please refer to our factsheets below which contain all the necessary information and links:
- Considerations before installing a barn owl box
- Instructions for building your own barn owl box
- A guide to choosing the right tree for your box
- Links and contacts for buying and installing a box
A short film showing a barn owl nest box being checked by licensed monitors:
Record your sighting
To help us get a better picture of where barn owls are, it is vital that you record your sightings.