Occupancy models of focal bird species in central Sierra Nevada foothill woodlands, California

This project was designed to assess if the California Native Plant Society Vegetation Monitoring Program (CNPS VMP) provides habitat data useful for predicting bird distributions. In 2004-2005, point counts for bird occurrences and relevé vegetation surveys following the CNPS VMP protocols were completed in the Sierra Nevada foothill blue oak (Quercus douglasii) woodlands of Yuba and Nevada Counties, California. Bird occupancy models were built in program PRESENCE using CNPS relevé data for twelve birds listed as focal species in the California Partners in Flight document The Oak Woodland Bird Conservation Plan. For nine species, site occupancy (ψ) and probability of detection (p) showed strong associations with CNPS relevé covariates. Estimates of occupancy that accounted for imperfect probabilities of detection were generally 20-30% higher than naïve estimates of occupancy for each bird. The results show the CNPS relevé data include important habitat variables useful for species-specific explanatory bird occupancy modeling within Sierra Nevada foothill hardwood rangelands. Further work should focus on the evaluation of existing models as well as on the development of new occupancy models for birds in different habitats using the CNPS vegetation monitoring program data.