Fledge spotting: Peregrine falcon pair nesting on Alcatraz island

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Side-by-side photos two peregrine falcons, male on left and female on right.

For the first time in recorded history, peregrine falcons have nested on Alcatraz Island!

When park biologists first spotted two peregrine falcons on Alcatraz Island in winter of 2019, it wasn’t clear whether anything special was going on. It isn’t unusual to see peregrines on Alcatraz during the fall and winter months, and they usually depart by February. But as biologists observed the pair staying active on the island throughout the summer and fall, the prospect of the peregrine pair mating and nesting became less far-fetched.

These powerful birds of prey can dive at speeds of up to 200 mph, making them one of the fastest known birds in the world. They have a unique conservation success story. During the mid 20th century, peregrines nearly went extinct from human use of pesticides like DDT. But thanks to Environmental Protection Agency bans on DDT and robust species recovery efforts, peregrines were removed from the endangered species list in 1999. Their story is an inspiring example of how humans can coordinate to help vulnerable species bounce back. 

After observing the pair on Alcatraz, biologists soon noticed the female was banded, and later confirmed she was "Lawrencium," a chick born in the iconic UC Berkeley Campanile tower. Lawrencium was banded in 2018 by the Santa Cruz Predatory Bird Research Group, a 40-year partner of the National Park Service that has worked on peregrine restoration across National Parks like Yosemite, Crater Lake, Channel Islands, and of course, the Golden Gate National Parks, where the Golden Gate Raptor Observatory runs long term monitoring of migratory raptors. Given that peregrine chicks have high mortality risk in their first few years, biologists were thrilled to see Lawrencium thriving.

But it still wasn’t clear whether Lawrencium and her companion were actively nesting on Alcatraz.  On March 3, 2020, park biologist Tori Seher spotted the pair mating on the Alcatraz water tower. Several days later, the male falcon repeatedly dive-bombed Seher near the western cliffs of the island, indicating the likely presence of a nearby eyrie (raptor cliff nest). In the months that followed, biologists observed the male sharing prey items with the female before she disappeared again somewhere along the cliffs. 

Young bird balances on a wooden beam

In early June, biologists were elated to see two fledglings appear, eating and testing their wings while their parents sat nearby. They've taken a few short flights, but are still wobbly in the air.

It’s still too early to say whether the peregrines will become a regular part of the diverse cast of avian species on Alcatraz island, or what implications that would have for the resident nesting seabirds. Park biologists will be watching closely as the fledglings grow and the story continues!

 

Maritte O'Gallagher

Maritte O'Gallagher started as a Science Communications Intern for the National Park Service in October 2017 and is now a Science Communications Assistant for the Parks Conservancy.