Wildlife Watch: Barn owls could have died due to heavy snow
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In late January my son informed me he had found a cluster of feathers from a barn owl inside the edge of an open coniferous wood at Blackhills, near Lhanbryde.
He reckoned a goshawk had killed, plucked and eaten the owl because he saw a juvenile female goshawk in the area where the remains of the owl was found.
As my son’s assertion that a goshawk had killed the owl was based on circumstantial evidence I challenged him on his viewpoint. I suggested that one of a pair of buzzards that nest in the wood may have found the owl dead of starvation following a period of lying snow in mid-January that lasted about a week.
Barn owls cannot hunt successfully when the lying snow is deep because field voles, which are the owls’ main prey, are hidden under the snow.
My son said that he visited the wood regularly and had not seen the buzzards for some time. He still insisted that it was highly likely that a goshawk had killed the owl because he had filmed a goshawk earlier in the year using a trail camera set by the half- eaten carcase of a hen pheasant he found.
The filming took place only a few hundred metres from the pluckings of the owl. The goshawk had returned to the pheasant carcase the next day to finish its meal and was caught on camera.
Given that there had been deep lying snow prior to my son finding the pluckings of the owl I had to concede that a goshawk might have caught and killed the owl during the hard weather as barn owls are often forced to hunt during the daylight hours to try to find food. The owls’ slow flight would make them vulnerable to attack by the faster flying goshawk.
Under normal circumstances barn owls would be hunting during the hours of darkness and would not be available as prey to the day-flying goshawk.
A few days later my son found another dead barn owl in a stubble field near the village of Portgordon. On this occasion the carcase of the owl was intact and there were no signs of injuries on its body.
Right away I suggested that this owl probably died of starvation during the hard snowy weather but my son said he examined the carcase of the bird and it had plenty flesh on its breast.
If it had died of starvation it would have had a knife-edge sternum or breastbone which is the classic sign of starvation in birds. So the reason for the death of this owl appeared to be a mystery.
However, there could be another reason for the owl’s death and this could have been by secondary poisoning from eating rats or mice that had been poisoned by rodenticides.
Post mortems of barn owls found dead in Scotland between 1991 and 2000 showed that six per cent of them had potentially lethal levels of rodenticide in their livers.
Barn owls found dead in England in recent years have also been found to have rodenticides in their livers. The rodenticide was identified as an anticoagulant called Brodifacoum which is apparently available to the general public online.