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Several studies have demonstrated that snowy owls Nyctea scandiaca defend an area around their nests against predators, hereby inadvertently creating safe havens for breeding dark-bellied brent geese Branta b. bernicla. However, studies investigating brent goose breeding ecology within the predator-exclusion zones of the snowy owls are absent. In 1999 and 2005, years of high lemming abundance Lemmus sibiricus and Dicrostonyx torquatus, brent geese were primarily breeding in association with snowy owls in the Medusa river catchment on western Taimyr, Russia. Goose nest failure, either as a result of nest abandonment by the adult birds or of nest depredation, increased with increasing distance from the owl nests. Within the brent goose colonies, clutch size as well as egg size increased with decreasing distance from the snowy owl nest, indicating an increasing adult quality closer to owl nests. However, as a result of the abandonment of eggs and goslings, the increasing clutch size did not result in a higher nest success during this study. Apparently brent geese compete for breeding sites close to owl nests, but details of this process remain unknown. [ABSTRACT FROM AUTHOR]