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    Author(s): Joseph L. GaneyWilliam M. Block; Jill K. Dwyer; Brenda E. Strohmeyer; Jeffrey S. Jenness
    Date: 1998
    Source: Wilson Bulletin. 110(2): 206-217.
    Publication Series: Scientific Journal (JRNL)
    Station: Rocky Mountain Research Station
    PDF: Download Publication  (986.57 KB)


    We monitored dispersal movements of 19 radiotagged juvenile Mexican Spotted Owls (Strix occidentalis Zucida) in northern Arizona during 1994 and 1995. All juveniles initiated dispersal movements in September or October during both years, with most dispersing during September. Initial dispersal movements were rapid and abrupt, but lacked a significant directional pattern. Distance from the nest to the last observed location and the most distant location reached ranged from 0.6-72.1 and 2.1-73.5 km for individual owls, respectively. These distances represent minimum estimates of dispersal capability because only one individual was tracked until it settled on a territory and paired. Owls used a variety of habitat types during dispersal, some of which differed markedly from typical nesting habitat for Mexican Spotted Owls. Four of five owls that were tracked past mid-November moved to lower elevation pinyon-juniper woodlands and at least one overwintered in pinyon-juniper woodland. Kaplan-Meier estimates of annual survival rate ranged from 20.5-28.7%, depending on whether we censored all owls with unknown fates or included suspected deaths as mortality events. Estimates differed significantly between years and confidence intervals were wide, suggesting that longer-term studies of lame numbers of owls will be reauired to obtain accurate and precise estimates of juvenile survival.

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    Ganey, Joseph L.; Block, William M.; Dwyer, Jill K.; Strohmeyer, Brenda E.; Jenness, Jeffrey S. 1998. Dispersal movements and survival rates of juvenile Mexican Spotted Owls in northern Arizona. Wilson Bulletin. 110(2): 206-217.


    Mexican Spotted Owls, Strix occidentalis Zucida, dispersal movements, survival rates

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