| The San Clemente Bell's sparrow (Artemisiospiza belli clementeae) is a federally threatened subspecies endemic to San Clemente Island, California. This subspecies was previously considered dependent on boxthorn (Lycium californicum) habitat for nesting. However, recent reestablishment of native shrubs other than boxthorn on San Clemente Island has been accompanied by an expansion of the breeding range of the San Clemente Bell's sparrow into areas not historically considered suitable. To explore sparrow breeding ecology in these new habitats, we modeled daily survival rate (DSR) for 200 nests found from 2013-2015, comparing boxthorn habitat to other habitats at 3 spatial scales. Estimated DSR ranged from 0.960 (SE 0.007) in 2014 to 0.979 in 2013 (SE=0.005), with more variation due to year and date of nest initiation than by habitat type. The breeding success of Bell's sparrows in non-traditional areas where shrub species other than boxthorn have recovered suggests the previously described reliance on boxthorn may have been based more on availability than preference. Our findings illustrate how endangered species populations may respond in unexpected way to recovering landscapes, and emphasize the importance of adapting conservation and monitoring efforts accordingly. |