Purple Martins in Oak Woodlands

Purple martins are cavity-nesting swallows that once nested fairly widely in California’s oak woodlands but are now rare in that habitat. The old oaks of the Tehachapi Range (southern Sierra Nevada) may now host the last martins that nest in oak woodlands, with approximately 100-200 pairs or about 15 percent of the California population. In summer of 2000, we found 57 nests in 46 valley and blue oaks and measured over 20 variables at nest sites and random paired sites. Martins selected large-diameter trees [ x = 104.3 cm diameter at breast height (dbh)] that were more prominent than random trees. Among all trees with holes, martins chose nest trees that were prominently positioned in the upper third of the landscape, and had less canopy cover at nest height than random sites. European starlings were uncommon where martins concentrated, and starlings were not observed at one area with 18 martin nests; this was the only area >1 km from any residential development. Martins may persist in portions of the Tehachapi Range because of a unique set of habitat and landscape conditions, including factors that seem to limit starlings to low densities.