According to one study of the years 1994 to 2000,
 In Irruptive years (1995, 1999):
*A larger number of owls migrate
*Dominated by Hatch Year birds
*Body mass and body-condition indexes significantly lower for all owls, and particularly for immature owls – evidence of competition for the available resources
*Low-Recapture Rate: A smaller number of owls elect to stopover
*Population of prey species along the migration route can diminish quickly, and the owls in good condition move on sooner “…minimizing length of stopover to the extent that energetic condition allows.”
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