Recovery Plan for the Northern Spotted Owl - DRAFT

In summary, even with optimistic assumptions about juvenile survival rates,the best information suggests that the population of resident, ternitorial owlshas declined, on average, at an estimated rate of 7.5 percent each year duringthe 1985-91 period and that this rate of decline probably has accelerated inrecent years.Senescence is another potential problem: unaccounted for senescence leads tooverestimation of X. Likewise, it seems clear that fecundity is overestimatedeach year and this overestimation is more severe in years of poor production.K Table C.7. Estimates of average adult female survival (¢) \during 1985-91 for the northern spotted owl, based on thebest model out of 64 for the pooling of data across the fivestudy areas.Year ie( 0)1985-86 0.8880 0.02421986-87 0.8727 0.02021987-88 0.8556 0.01571988-89 0.8367 0.01241989-90 0.8158 0.01461990-91 0.7929 0.0231!Table C.8. Estimates of the finite rate of annual population change (x) for the northernspotted owl obtained by pooling all the data across the five study areas. Cases(explained in the text) make differing assumptions about juvenile survival rates.A~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Case Years Female xae(X) cJz PSurvivalRatea~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1 1985-86 Declining Omax1a 0.9813 0.0373 -0.4879 0.31281 1990-91 Declining Omaxia 0.8857 0.0362 -3.1575 0.00082 1985-91 Constant Omaxl 0.9259 0.0312 -2.3750 0.00883 1985-86 Declining Omax 2 b 0.9805 0.0322 -0.6056 0.27243 1990-91 Declining Omax2b 0.8844 0.0312 -3.7051 0.00014 1985-91 Constant Omax2 0.9246 0.0251 -3.0040 0.0013a The survival rate of juveniles was used for the area with the highest survival rate.The year with the highest survival was used for the Medford and Roseburg areas, thus the emigration was lowest.- . _ . ................................................. ,, , ............. . ..... ,327