Barn owls and development: survey and mitigation

Barn owls are listed on Schedule 1 of the Wildlife and Countryside Act 1981, which means it is an offence to intentionally or recklessly disturb one while it is nesting, or to disturb its dependent young, on top of the general protection given to every wild bird's nest. For anyone converting a barn or a rural outbuilding, barn owl survey planning work therefore has to happen before the roof comes off rather than after a neighbour reports a bird. The species also has no tidy survey season, which changes how you programme the work.

A barn owl in the building is rarely fatal to a scheme. Finding one halfway through the strip-out usually is.

Protection under the Wildlife and Countryside Act 1981

Two layers apply. Section 1 protects all wild birds, their eggs and their nests while in use or being built, so damaging an active nest of any species is an offence. Schedule 1 adds a further offence of intentionally or recklessly disturbing the bird while it is building a nest, or is in, on or near a nest containing eggs or young, and of disturbing its dependent young.

Barn owls are not European protected species, so the licensing route that applies to bats and great crested newts does not apply here. What that means in practice is that the emphasis falls on avoidance and timing rather than on a mitigation licence, and that the offence is judged on what you knew or should have known.

Recklessness is the word that does the work. A developer who has been told owls use the building, and who proceeds anyway without checking, is in a much worse position than one who commissioned a survey and acted on it.

Where barn owls turn up in development

Old farm buildings with open gables, broken windows and undisturbed lofts are the obvious places. Owls also use hollow trees, church towers, grain stores, disused stables, hay and straw stacks, and nest boxes put up by previous owners who then sold the farm.

The signs are distinctive and easy to learn. Accumulated pellets, often in layers several centimetres deep beneath a favoured perch. Whitewash streaking down walls and beams. Moulted feathers. A shallow scrape in a pellet debris layer on a beam or in a loft corner, which is what passes for a nest. Live birds flushed during a daytime inspection.

Nest boxes matter legally as much as natural sites, because a box in regular use is a nest site. Removing one that was put up ten years ago is not a neutral act.

Survey evidence and its timing

Start with an internal and external building inspection by an ecologist, looking for the signs above. That inspection can be done at any time of year, which is useful, and it is normally part of a Preliminary Ecological Appraisal covering bats and birds together.

Where signs are found but occupancy is unclear, the ecologist will usually add dusk and dawn activity watches during the breeding period, recording birds entering and leaving. Two or three visits is typical.

Timing is where barn owls differ from most species. They can breed across a very wide part of the year, with laying most often from spring into summer but second broods running well into autumn and occasional winter nesting in good vole years. There is no reliable four-month window in which the building is certain to be empty. That makes survey validity short, and it means a check immediately before works start is sensible even where an earlier survey found nothing. Barn owls share their buildings with bats often enough that the Bat Survey usually runs alongside, and the two have different seasonal constraints.

Designing a conversion around a nest site

The aim is to keep a usable nest site on the holding, in a place that survives the conversion and the occupation that follows.

Retaining access into the converted building itself rarely works, because owls and habitable rooms do not mix, and because new owners block the openings within a year. The approach councils accept most readily is a dedicated provision elsewhere: a nest box in a retained outbuilding, an owl loft built into a cart shed or garage that is not being converted, or a pole-mounted box in the right position on adjoining land.

Position the provision before the layout is fixed. A box on the north elevation of a building that later gets a home office window beneath it will fail. Work out where the birds will hunt as well, because a nest site with no rough grassland within reach is decoration rather than mitigation.

Mitigation councils accept

A mitigation package that gets through officer scrutiny usually contains most of the following.

A named alternative nest site, shown on a drawing with its height, orientation, entrance dimensions and mounting detail, sited away from busy roads. Standard advice is to avoid positioning boxes close to motorways and dual carriageways, because road mortality is a recognised cause of barn owl deaths.

Retention or creation of rough tussocky grassland for hunting, typically as wide field margins, headlands or a strip along a watercourse, with a cutting regime that leaves the sward long through the winter. Owls hunt small mammals living in that layer, and a mown amenity margin supports almost none.

A lighting scheme that keeps the nest site and the flight lines dark, with no upward spill onto the box and no floodlighting of the yard it faces.

A method statement setting out timing of works, supervision by the ecologist, and what happens if a bird is found once works have started.

Conditions and timing restrictions

Expect a condition requiring the approved ecological mitigation to be installed before first occupation and retained thereafter, and often a condition restricting demolition or roof works to periods outside the breeding season as advised by the ecologist.

Read the wording. A condition restricting works to the months of September to February assumes a season barn owls do not always keep, and it can be both too restrictive for your programme and insufficient to protect the birds. A better condition requires works to proceed only following a pre-works check by a qualified ecologist confirming no active nest is present, with a written record supplied to the council.

Where the mitigation is a box in someone else's ownership, the council will want it secured, either by including the land in the red line or through an obligation.

Licences and when they are needed

Survey activity that would disturb a nesting Schedule 1 bird requires a licence from Natural England, so an ecologist inspecting an active nest closely, or using a camera at the nest, needs to hold one. Straightforward external inspection and activity watching from a distance do not.

For development, there is no general mitigation licence equivalent to the European protected species regime. The position is that you avoid committing the offence. If works cannot avoid disturbing an active nest, they stop until the young have fledged, or a licence is sought from Natural England for the specific purpose, which is granted only in limited circumstances.

Commission the Protected Species Survey from a suitably qualified ecologist. A licensed or competent professional is legally required for protected species work, and a PlanScope draft is a starting point for that professional rather than a substitute for them. The habitat you create for owls will also register on the statutory metric behind your Biodiversity Net Gain Assessment, so it is worth designing the two together.

But the timing point is the one to remember. Get the building inspected in the winter before you want to start, and the rest of it is manageable.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.

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