TAWNY OWLS AND THEIR PREY

Abstract

Summary.1. This paper follows over eight years the diet of some 20 pairs of Tawny Owls Strix aluco living in woodland.2. Pellets were collected regularly and the prey‐remains in them were identified. Much information about the territorial and hunting habits of Tawny Owls was gained.3. There is a regular seasonal swing between small rodents (especially Wood Mice and Bank Voles) and larger prey (young Moles, Rabbits and rats). The former predominate in winter and spring, the latter in summer and autumn. This fluctuation is regular year after year with these animals, whereas shrews and small birds are eaten in small numbers steadily throughout the year and from year to year.4. Small rodents are eaten most when ground cover is sparsest, which may account for the early breeding season of the Tawny Owl. By the beginning of May, when vegetation is becoming dense and mice and voles are difficult to find, the young are already well‐grown and can deal with the food brought to them. The hen is, therefore, free to go hunting herself and both parents must work hard for the next three months while the young are still dependent on them.In more open country Barn and Short‐eared Owls seem to time their breeding later so that they are feeding their young on the big crops of Short‐tailed Voles and–to a smaller extent–of shrews.5. This long period of dependence of young Tawny Owls falls when there are plenty of young Moles, often a large crop of cockchafers and generally plenty of earthworms to fall back on. The brownish, fibrous pellets of Tawny Owls are now known to contain mainly the chaetae of earthworms, which are sometimes brought to the young in very large quantities.6. Analysis of the results by locality shows that Tawny Owls take only the prey species which are available in their immediate vicinity. This and other evidence proves them to be strongly territorial and it is suggested that only by having a territory and knowing it intimately can a Tawny Owl survive.