Biologists from PRBO Conservation Science just published a report of fifteen years of song bird monitoring on the Mt Tamalpais Watershed. The news is good, with most bird species stable or increasing, indicating that the 21,000-plus acres of land managed by MMWD continue to provide important wildlife habitat.
Compared to population trends estimated for California from breeding bird surveys, more bird species on the watershed had stable populations than elsewhere in the state and many species that are declining elsewhere are stable.
“We’re pleased to know that our bird populations are stable,” says MMWD Natural Resources Program Manager Janet Klein. “The stewardship of our natural resources is an important part of what we do, and bird monitoring is one of the ways we keep track of how we’re doing.”
Of the 42 species monitored since 1996, 86 percent showed no change in population size; two species (Anna’s Hummingbird and Olive-sided Flycatcher) increased in abundance; and four species decreased in abundance (Steller’s Jay, Western Scrub-Jay, Spotted Towhee and California Towhee).
The declines in the jay populations may be due to two factors. Jays are susceptible to West Nile virus and their primary food source of acorns has been compromised by Sudden Oak Death Syndrome (SODS). The other species showing declines and increases may also be responding positively or negatively to habitat change by SODS, changes in food availability, climate, or a combination of these factors.
The results of the study highlight the importance of MMWD lands for birds, and the importance of monitoring populations to detect changes early.
Click here to view the full report.