The Trust's work - prevention of drowning
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The fact that birds drown in steep-sided water containers comes as a surprise to many people and for some reason owls and raptors seem particularly prone to it. The most remarkable case we have come across was of a cattle trough next to a farm building in south Devon. Whilst removing the body of a recently drowned (still floating) Barn Owl, we noticed the remains of another bird at the bottom of the tank. Eventually we emptied the tank and discovered the remains of another Barn Owl, two Little Owls and a Kestrel.
A post-breeding wash
Most cases of Barn Owls drowning occur during the summer and many of the birds affected are breeding females that have emerged after 6-7 weeks of incubation and brooding young. Recently fledged Barn Owls seem particularly prone to drowning as well. The loss of breeding females is particularly disappointing as breeding adults are the most important birds in the owl population.
Steep-sided cattle troughs, whether they are full to the top or only part-filled are where most drownings occur but dead owls have also been discovered in garden water butts, horse water buckets, oil containers and even slurry pits.
Water containers can easily be made safe by floating some sort of mesh just below the surface - buoyant enough to support a 350g owl but easy for farm stock to push down when they drink. Some types of plastic bread tray work quite well and apparently some types of plastic doormat do as well. Unfortunately the ones we have tried generally sink! The size and shape of water troughs is so variable that usually the best solution is to produce a purpose-made float for each tank. The Barn Owl Trust uses a simple frame of treated timber fitted with strong plastic mesh and plastic foam for permanent buoyancy. At some sites these have already lasted for nine years but many don't last that long. Troughs for cattle confined in a yard are a particular problem. Generally, anything not made of steel, stone, or very heavy timber is soon trashed. However floats in field troughs usually last at least a few years.
Whilst carrying out various conservation schemes we have protected all the troughs within 200 metres of each nest and this certainly seems to have prevented birds from drowning. Because floats sometimes need to be replaced, and can easily be removed by anyone who is unaware of the reason for them, they are only a long-term solution where there is ongoing effort. In order for that effort to be directed for maximum benefit, it is suggested that steep-sided water containers are made safe -
- Within 200 metres of active nest sites (starting with the closest one).
- Where birds have previously been found drowned.
In cattle farming areas, making all water containers safe is generally not a practical proposition. The ultimate solution is for water trough manufacturers to design bird-friendly tanks.
There is more information on this and many other topics in the Barn Owl Conservation Handbook