Prey caching of breeding Tengmalm's owls Aegolius funereus as a buffer against temporary food shortage

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Prey caching of breeding Tengmalm's Owls was studied for 13 years in western Finland. Stores were observed only in nest-holes and they mainly (72%) contained voles. Cached prey was recorded mostly during egg-laying and hatching when females and, especially, young cannot withstand long periods of food shortage. Prey stores were largest in vole peak years when breeding was earliest and the risk of experiencing adverse weather conditions was highest. The number of prey items stored was higher both before and after the snowfalls than during such intervals. This supported the hypothesis that prey caching is a buffer against temporary food shortage in the breeding season. Those Tengmalm's Owl pairs, near which (≤ 1 km) other vole-eating birds of prey bred, had smaller prey stores than 'non-neighboring' pairs. This was in disagreement with the hypothesis which states that prey caching may secure food resources when several coexisting predator species have similar prey preferences. Among North European owls, only the two smallest species (Pygmy Owl and Tengmalm's Owl) make large food stores. The following factors seem to be important for the evolution of food caching in owls: small body size, cold, variable climate causing temporary food shortage and availability of safe caching places.

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Reference Code: A86KOR02IDUS

Full Citation: Korpimaki, E. 1987. Prey caching of breeding Tengmalm's owls Aegolius funereus as a buffer against temporary food shortage. Ibis 129(Supplement s2): 499-510.

Location: ANIMAL EF: AEGOLIUS FUNEREUS