Sad end for a well travelled barn owl

25th September 2013
Sad end for a well travelled barn owl

Barn Owl (c) Kevin Keatley
By John Woolsey, Barn Owl Officer, Ulster Wildlife

At the end of April this year, a Co Down farmer contacted me with the sad news that he had found a dead barn owl in one of his farm sheds. This farmer is well known to me as he has a barn owl nest site on his land and he carries out his farming activities with an eye on his local wildlife. I collected the owl carcass and apart from identifying it as a female bird and in good condition prior to death, I noticed that the bird had a BTO leg ring. This was unusual for a NI barn owl casualty as no-one is currently leg ringing barn owls here. I forwarded the ring number to the British Trust for Ornithology and delivered the carcass to AFBI Veterinary Sciences Division for a post-mortem examination.

Surprising information came back from BTO – the bird had been ringed as a nestling on 9 August 2009 at a confidential site near Hawkins Point, East Riding of Yorkshire, almost 400km from where it was recovered in Co Down! Although there are records of barn owls travelling from continental Europe into southern England and also of birds being found on ships and oil rigs, I have no records of birds making a journey like this example. Unfortunately it is impossible to know how long the bird had been in NI or if it ever had a chance to breed here and add to our small population of local barn owls.

Final results from the post-mortem came in last week and although they showed no definite cause of death, the barn owl had traces of two chemicals commonly used in the manufacture of rodenticides – Difenacoum and Flocoumafen. I have discussed the results with scientists from the UK wide Predatory Bird Monitoring Scheme and whilst the level of Difenacoum can be classed as ‘background’ i.e. unlikely to have been a major contributory factor, the level of Flocoumafen was at a level more likely to have been a contributory factor in the death of this bird.

Sadly, this case echoes the recent reports from a collaborative study between BirdWatch Ireland, University College Cork and the UK Centre of Ecology and Hydrology. This study has shown that more than 85 per cent of Irish barn owls had detectable traces of rodenticides in their systems before death.

Knowing the regard that this farmer has for all wildlife, especially barn owls, and knowing the care he takes to avoid, as far as possible, the use of rodenticides, I have no reason to think that the barn owl ate rodenticide contaminated prey on this farm. Over a single night of hunting, a barn owl may travel up to 8km radius from their roost site and so they can pick up prey from a wide variety of locations. Prey species including those that have eaten poisoned bait can travel between farms and it would be difficult to accurately establish where this barn owl caught and ate contaminated prey species.

Ulster Wildlife recognises and supports the obligation on farmers to control pests to help maintain biosecurity integrity within the agri-food industry. However, control measures involving rodenticides may pose a risk of secondary poisoning to non-target species such as the barn owl and for that reason rodenticides should only be dispensed when absolutely necessary and always in accordance with the manufacturers recommendations.

The current population of breeding barn owls in NI is unknown but it could be fewer than 50 pairs, any improvement on that figure depends on birds living longer and successfully rearing more young. It is clear that secondary poisoning from rodenticides has the potential to significantly impact on our raptor populations and for this reason Ulster Wildlife is supportive of the work being done by the Campaign for Responsible Rodenticide Use (CRRU) and its associated code of good practice, details of which can be found at

For more infomation on our Be there for Barn Owls Project