Barn Owl Survey
This survey aims to establish breeding densities of Barn Owls across three 10km2 areas in West Offaly. The squares selected for this survey are, IN 01 which encompasses Banagher and its surrounding town lands, IN 02 which has Belmont as its centre and IN 12 which has Boora Parklands just to its south and Ferbane in the west of the square. Results from this strategic survey, along with that of a mirrored project being undertaken by my colleague Michael O’Clery in Duhallow1, are hoped to provide inference as to the national population of breeding Barn Owls in Ireland.
Specifically, how does one survey for Barn Owls?
Each 10km square is surveyed individually, by travelling across the square and assessing all building’s suitability for Barn Owl nests. Although Barn Owls do on occasion nest in tree cavities, it was deemed unfeasible to survey trees for the purposes of this survey; an account of this will be taken in the final analysis. A suitable building for a Barn Owl must at a minimum provide a cavity for the nest site and have low levels of disturbance. This is most often found in ruined buildings where an old Jackdaw’s nest provides a platform within the chimney (Barn Owls pictured in a chimney below). Other favoured sites are crevices which provide access to a wall cavity in a ruined castle or mansion house.
Having at this point eliminated all unlikely buildings, promising buildings are now surveyed in detail; with permission to enter received from the owner. Likely buildings are meticulously searched for any and all evidence of Barn Owl activity. Any chimneys on site are examined for the presence of old Jackdaw nests, the interior and exterior walls are inspected for white washing (this can look like drops of white paint on the walls) and the property is scrutinised for pellets (Barn Owl pellets pictured below). Pellets are regurgitated hair and bone fragments which the owls cannot digest2. If fresh pellets are found in the building it is flagged as potentially active and a roost watch is undertaken. All suitable buildings, however, even if found unoccupied, are recorded; thereby quantifying nest site availability within each 10km square.
As Kestrels, Peregrine Falcons, Ravens and Jackdaw all frequent similar haunts, any of these species found on site are also recorded. Given the inaccessibility of Barn Owl nests predation is unusual, however, Pine Martens can access nests and, as such, evidence of their presence is also recorded for predation risk models.
1. John Lusby, Raptor Conservation Officer with BirdWatch Ireland said “Duhallow, which is an area encompassing parts of North Cork and East Kerry seems to be particularly suitable for Barn Owls, the local population appears to be doing well here and we have recorded one of the highest known densities of nest and roost sites in the country. Given the fact that Barn Owls have declined so markedly in other parts of the country, areas such as this are crucial for the conservation of the national population”
2. These pellets provide an invaluable insight into the diet of Barn Owls. Individual bone fragments can be identified and a catalogue then created of the species on which the owls prey. In 2008 a discovery of some interest was found in Barn Owl pellets in Co. Limerick. A previously unheralded alien species, the White-toothed Shrew was discovered through pellet analysis to be resident in the locality.