Measuring the health of Mt. Tam

Maintaining a healthy, vibrant and diverse Mt. Tam begins with understanding how key ecological resources are faring, and how we can better care for this iconic and beloved place.

One Tam partners and Bay Area scientists have come together to try to answer the question: How healthy are Mt. Tam's natural resources?

Conifer Forest Birds

Conifer Forest-Mixed Hardwood Forest Birds

Photo by Alan Schmierer

Summary

The overall condition of conifer forest-mixed hardwood-associated birds is Good.

Point Blue Conservation Science analyzed patterns of abundance from 1996 to 2013 to determine the trends for as many individual species as possible (see References below). Trends were determined for 14 of the 19 conifer forest-mixed hardwood-associated species. Trends for the Osprey and Northern Spotted Owls were determined through other species-specific surveys (see References below). Trend for the Varied Thrush was based on data from Audubon’s Christmas Bird Counts and trend for Sharp-shinned Hawk from the Golden Gate Raptor Observatory.

The vast majority of birds in this group are doing well and data was sufficient to assess condition with high confidence. One species of concern, the Olive-sided Flycatcher, is increasing on Marin Municipal Water District lands despite four decades of strong and consistent range-wide declines. This species has been positively associated with openings in the forest from fire and other disturbances. Hence, it is possible that the many forest openings caused by Sudden Oak Death have had a positive effect on Olive-sided Flycatcher.

Condition, Trend, and Confidence for Conifer Forest Bird Species Included in This Analysis

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References:

Cormier, R. L. (2015). Northern Spotted Owl monitoring on Marin County Open Space District and Marin Municipal Water District Lands, 2015 Report. Petaluma, CA: Point Blue. Available here.

Cormier, R.L., Seavy, N.E. & Humple. D.L. (2014). Abundance patterns of landbirds in the Marin Municipal Water District: 1996 to 2013. Point Blue Report. Available here

Ellis T. & Harrigan K. (2016). Monitoring Northern Spotted Owls on Federal Lands in Marin County, California: 2013 Report. Natural Resource Report. NPS/SFAN/NRR—2016/1180. National Park Service. Fort Collins, Colorado. Available from: https://irma.nps.gov/DataStore/DownloadFile/548251.

Shuford, W. D., & Gardali, T. (eds.). (2008). California Bird Species of Special Concern: A ranked assessment of species, subspecies, and distinct populations of birds of immediate conservation concern in California. Studies of Western Birds 1. Camarillo, CA: Western Field Ornithologists, and, Sacramento: California Department of Fish and Game. Available from https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=10513