An opportunity to see these Osprey live in their nest. 


Ospreys started nesting on Mare Island between 2000 and 2005, only rarely nesting in the San Francisco Estuary prior to 2005. By 2013, there were 26 nesting pairs of ospreys estuary-wide; including 14 pair nesting on Mare Island. Osprey exhibit site fidelity, which means that the same birds will come back to use the same nest year after year. With a body that is 2 feet long and a wing span of 6 feet, osprey are easy to spot soaring over north bay waters hunting for fish which they bring back to the nest or eat while perched on an adjacent pole.

What makes Mare Island good osprey nesting habitat?  It’s all about availability of fish for them to eat and good nesting locations.  Mare Island is situated at the mouth of the Napa River where fluvial outflow (fresh water coming down the river) meets Delta outflow from the Sacramento and San Joaquin Rivers and tides from the Pacific Ocean. This mixing zone is fertile fish habitat and the fish have become more visible now that the water is clearer because its sediment load has decreased.

Island Energy and California Fish and Wildlife installed the wagon wheel design nest platform on March 5, 2015, after an osprey was accidentally electrocuted on a nest built too close to high voltage wires.

Earlier Osprey Nest On Wire

New Walnut Nest

Osprey In New Walnut Nest

Almost immediately after it was erected an osprey pair started building the Walnut Nest, so named because it is located at the junction of Walnut Avenue and SR-37, at Mare Island’s North Gate.

The osprey’s activities at the nest site have an annual rhythm to them, a regularity that occurs within a range of dates each year. Osprey return to the Walnut nest on Mare Island in late February or March to add sticks and do maintenance on the wagon wheel nest. Eggs are laid in March or April and incubated for 32-43 days.  This pair have hatched 12 eggs between 24th of April and the 21st of May and the young birds fledge (fly from the nest) in 48 to 59 days from when they hatch,  some time between the 22nd of June and 30th of July.  (Data courtesy of Tony Brake who observes the Walnut nest for the Golden Gate Raptor Observatory.)

The Friends conceived the osprey live nest camera project as a way to bring nature directly to people’s computers.  We have been fortunate to partner with Island Energy who installed the nest platform and camera equipment that was funded by Ducks Unlimited and Cargill to bring life in an osprey nest onto the web.  Doug Buchanan and his crew at Island Energy deserve extra kudos for the perseverance and patience they’ve needed to work through unanticipated start-up camera issues. 

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