Reproductive Success of Black-Crowned Night-Herons and Snowy Egrets on Alcatraz Island

Science Center Objects

Years after the last inmate departed Alcatraz Island, waterbirds like Black-crowned Night Herons and Snowy Egrets still make the forbidding island their home. The National Park Service has requested the aid of WERC’s Dr. Pete Coates to inform efforts to expand visitor access to the Island, and simultaneously maintain healthy waterbird populations.

At the National Park Service’s request, WERC’s Dr. Pete Coates studies the reproductive success of Black-Crowned Night Herons and Snowy Egrets on Alcatraz Island. The NPS wants to increase visitor access to the Island, while also maintaining Alcatraz’s waterbird populations.

NPS photo of a Black-Crowned Night Heron
(Public domain.) Credit: NPS. Photo of a Black-Crowned Night Heron on Alcatraz Island.

Alcatraz Island is a National Historic Landmark that lies within the Golden Gate National Recreation Area. Nestled in California’s San Francisco Bay, the Island’s history and beauty draw thousands of tourists each year.

Alcatraz also provides a more permanent attraction for colonies of water- and seabirds that fledge, mate, and raise their offspring on the rocky cliffs. Activities and events for visitors have the potential to disturb and even flush the birds from their nests, leaving eggs and chicks vulnerable to predators like ravens.

Dr. Coates and team are monitoring the distribution, abundance, and nesting behaviors of Black-Crowned Night Herons and Snowy Egrets to track any potential effects from tourist activities. The scientists will provide the NPS with annual reports to keep the agency informed of their latest study findings.