Ospreys (Pandion haliaetus) are apex avian predators commonly seen on the summertime shores of Lake Tahoe, California/Nevada. This species suffered severe declines across the United States due to egg shell thinning impacts from widespread use of the pesticide DDT. There was only one nesting pair at Lake Tahoe in the 1970’s when DDT was banned in the United States.  During the past three decades, Osprey numbers in the lake increased to almost twenty active nesting pairs in 2015. Emerald Bay State Park and the contiguous D.L. Bliss State Park have a range of 6-9 active nests each year. These parks contain the most concentrated area of active nests around Lake Tahoe. Emerald Bay State Park is also one of the most highly visited recreation areas on the lake and this high visitor use could present potential stressors to Osprey nest effort and success. From mid-September 2012 until mid-June 2016, the Eagle Point Campground in Emerald Bay was closed for remodels during which time there was a substantial decline in trail use and noise disturbance in proximity to a number of Osprey nest sites. This closure offered an opportunity to measure the potential influence of human disturbance on Osprey nest site selection and success. California State Parks biologists have been collecting Osprey nesting data since 2001 and have records from the United States Forest Service since 1976. The objective of this project was to analyze historic nesting data to determine patterns in nest selection and reproductive success in regards to areas of development and recreational use.

People: Jacobs, Albright

Key collaborators: Daniel Shaw (California Parks)

Funding: California Parks

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Relevant Publications: pending

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