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Wind Turbines and Barn Owls
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Wind Turbines and Barn Owls
The Barn Owl Trust is often contacted by people who are concerned about wind turbines and the effect they may have on their local Barn Owl population. Although it is true to say that wind turbines kill birds, the turbines involved are usually those that are poorly positioned and the victims are usually high-flying species rather than low-flying birds like Barn Owls.
The idea that all wind turbines kill thousands of birds originated from the Altamont Pass Wind Resource Area in California. This huge wind farm is very poorly positioned and although Barn Owl deaths have been recorded, these equate to only one death per turbine every 53 years. This level of impact is in sharp contrast to other hazards such as traffic collisions, which are estimated to kill between 3,000 and 5,000 Barn Owls in Britain every year. The Altamont Pass study involved the American Barn Owl, (Tyto furcata) which is partially migratory. Poorly positioned wind farms in Britain are less likely to have a negative impact, as Barn Owls in Britain do not migrate.
There is currently no evidence to suggest that wind turbines in the UK are having a significant effect on Barn Owls. So far, there is only one confirmed case of a Barn Owl being injured or killed by a wind turbine in Britian (on 04/01/13). While it is true that such deaths are likely to be under-recorded, the same could be said for many other causes of death such as starvation or flying into overhead wires but we do receive regular reports of these kinds of fatalities.
The Barn Owl Trust is in regular contact with the owners of a working livestock farm that has several Barn Owl nestboxes and a small/medium-sized wind turbine positioned close to and on the same level as one of the nestboxes. Over the last ten years, Barn Owls have nested within 500 m of the wind turbine on six occasions and within only 35 m of the turbine on three further occasions. On average they successfully fledged three young per year with no reported casualties. We are also aware of a site where Barn Owls nested successfully at least six times only 750 m from a wind farm comprising 16 massive turbines.
The main reason that Barn Owls are unlikely to be affected is due to the way they forage. As hearing is the primary sense utilised, Barn Owls must fly at comparatively low altitudes in order to hear their prey, typically not more than three metres above the ground. Most wind turbine blades have a ground clearance well in excess of this. Indeed, the only confirmed turbine-related death was of a Barn Owl killed by a low-level domestic turbine not a tall commercial one. Additionally, it is worth remembering that a wind turbine does not act like a propeller. Whereas a propeller accelerates air and actually ‘pulls in' objects in front of it, a wind turbine slows the air down. The chances of a bird flying through a powered propeller without being struck are almost non-existent, whereas birds sometimes fly through rotating wind turbine blades unharmed.
Monitoring at existing wind turbine/anemometer sites for Barn Owl injuries/fatalities is undoubtedly inadequate at the present time and mortality thus under-recorded. Given the likely proliferation of wind turbines, a strong argument exists for long-term (ideally independent) monitoring systems to be implemented at wind turbine sites. The simplest form of monitoring involves regular intentional searches for bird carcasses. However, the probability of dead birds being found is no doubt reduced by the removal of carcasses by scavengers. Carcasses may also be accidentally overlooked if not deliberately searched for, especially if they are not immediately underneath turbines.
The Barn Owl Trust suggests that new wind farm developments should be surrounded by fox and badger-proof fencing, that systematic carcass-search monitoring should be carried out for a period of not less than two years and that the results should be made public. In responding to planning applications, the Barn Owl Trust requests that Local Planning Authorities (LPA) should ensure that adequate monitoring is required by planning condition in line with a statement by the Minister for Energy and Climate Change.
The following suggestions are ways in which any potential impacts by wind farms on Barn Owls can be minimised;
- Proposals for new wind farms should include a full Environmental Assessment, including the close monitoring of the movements of high-flying bird species for a full 12 months.
- Tubular turbine masts should be preferred over lattice masts to reduce the risk of Barn Owls attempting to use the structure for perching.
- Where the bottom of the rotor arc is within 5 m of the ground, vegetation surrounding the turbines should be managed specifically to reduce the availability of small mammals to avian predators.
- New major wind farm developments should be surrounded by fox and badger-proof fencing. Fences should be positioned away from the mast base(s) in all directions and at a distance that is no less than the height of the mast plus the length of one blade. The fenced area must be searched for dead/injured birds and bats no less than once a week at all times of year for no less than two years. Monitoring results should be made public.
Wind anemometers are often a temporary pre-cursor to wind farm applications and are potentially more dangerous than turbines due their stabilising wires. In some cases there may be up to twenty stabilising wires per anemometer mast and Barn Owls can be at risk of flying into wires especially where they are positioned in areas of prime foraging habitat. Possible preventative measures include white-coated wires fitted with sound generating devices such as ‘humming lines'.