Peregrine Falcons May Be Nesting on Alcatraz, a First in Recorded History

In March 2020, the biologist on Alcatraz Island found herself being dive-bombed. A male peregrine falcon repeatedly swooped at her near the island's western cliffs — the kind of defense that signals a nearby eyrie, or nest. If the pair on Alcatraz really is nesting, it will be the first time in recorded history.

On March 3, the island's peregrine pair was photographed mating on the Alcatraz Water Tower. Credit: Tori Seher, National Park Service.

Unwelcome year-round residents

A pair of peregrines has been active on Alcatraz since January 2019. Leg bands identify the female as Lawrencium, hatched in 2018 on the UC Berkeley Campanile and named — in a university public poll — for an element discovered at Berkeley.

Peregrines often visit Alcatraz in fall and winter, but they usually leave by February. The year before, this pair stayed through spring and summer, much to the dismay of the island's nesting waterbirds. No bird seemed safe: the falcons regularly knocked other birds out of the air, sometimes right in front of startled tourists.

Signs of a nest

The male peregrine shares prey with the female before she disappears down the cliff, where biologist Tori Seher suspects the nest is. Credit: National Park Service.

• March 3: the pair was photographed mating on the Alcatraz Water Tower.
• Several days later: the male repeatedly dive-bombed the island biologist near the western cliffs.
• Since then: the male has been seen passing prey to the female, who then vanishes somewhere along the cliff below.

Sources

Based on "Peregrine Falcons May Be Nesting on Alcatraz," Bay Area Nature & Science Blog, Golden Gate National Recreation Area, National Park Service, March 2020; a work of the United States government in the public domain.