| The Botteri's Sparrow (Aimophda botterii) is a tropical and subtropical tallgrass specialist, highly vulnerable to habitat alterations. It virtually disappeared from the American Southwest following loss of grass cover caused by drought and overgrazing in the 1890's. Territory mapping, nest searching and monitoring, and color banding were used to determine breeding density, reproductive success, and site fidelity of Botteri's sparrows nesting in three distinct habitats in southeastern Arizona between 1999 and 2001. These habitats, from heaviest to lightest grass cover, were: (1) sacaton (Sporobolus wrightii), a dominant native tallgrass that grows along floodplains; (2) upland areas dominated by two introduced African lovegrasses (Eragrostis curvula var. conferta and Eragrostis lehmanniana); and (3) upland mesas of native short and mid-height grasses.; I monitored 323 Botteri's Sparrow territories, followed 314 nests to completion, and banded 600 birds on 18, 10-ha plots, six in each of the three habitats. Territory density was positively correlated with vegetation height and negatively correlated with the amount of bare ground available across all habitats. Although Botteri's Sparrow density was highest in sacaton, intermediate in exotic lovegrass, and lowest in native upland vegetation, young fledged per plot did not differ among habitats, apparently due to relatively (but not significantly) lower values of young per territory in sacaton in two of three years. |
