Capsule: Barn Owl pellets can be used to assess population changes in small mammals though with certain
important reservations.
Aims: To conduct a large-scale, long-term analysis of pellets regurgitated by Barn Owls collected from a
defined area of countryside within the UK south Midlands and compare results with those of other studies
that have used pellet analysis to investigate the diet of Barn Owls.
Methods: Over 61 000 Barn Owl pellets collected over 20 years in the south Midlands of England were
analyzed.
Results: We recorded a steady increase in the proportion of Field Voles in pellets over time at the expense of
Wood Mice, and a positive relationship between various rainfall measures and the proportion of Field Voles
in pellets.We suggest that the conclusions of previous studies of the diet of Barn Owls have often been predicated
on inconsistent or untenable assumptions.
Conclusion: We challenge some of the premises on which Barn Owl pellet analyses have traditionally been
based.We do not think that either a shortage of Field Voles in pellets, or of pellets containing the remains of
more, smaller prey items, are indicative of foraging difficulty. Barn Owl pellets can be used to assess population
changes in small mammals, so long as possible causes of bias, which we discuss, are acknowledged
