| Summary: | One pair of Short-eared Owls nested on Griend, an islet in the Dutch Wadden Sea, in 1992, 1994, 1995 and 1996. The species never bred on Griend prior to the 1990s. In the four years one, one, four and zero chicks fledged. Growth of the chicks showed differences corresponding with hatching order. Oldest chicks grew faster than their younger siblings. In 1996, chicks grew notably slower than in 1995. Pellets and plucking remains found in the immediate vicinity of the chicks revealed that Dunlins and Wood Mice made up 69 and 28%, respectively, of prey items in 1995. Other avian prey included Redshank, Turnstone, Common- and Arctic Tern. In 1996, however, Wood Mice made up 76% of prey items, while Dunlins accounted for only 8%. Timing of the start of the breeding season seems important for the Short-eared Owl on Griend. It is suggested that the islands' Wood Mice population alone does not allow for optimal growth and survival of owl chicks. When owls started breeding relatively early (1995: late March), Dunlins, present in large flocks, constituted an additional prey during the chick rearing period. This resulted in fast chick growth and good breeding success. In 1992 and 1996, Dunlins disappeared to migrate to their breeding areas one week after owl eggs had hatched; consequently, chick survival was low. Wood Mice were inadvertently introduced to the island in 1988.
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