The evidence is all around us: A trail of paw prints in the sand. A couple of droppings here and there. The carcass of a bird that, by at least one assessment, looks as if it’s been “picked clean.”

It’s just after daybreak on Alcatraz, where a coyote recently came ashore after a historic swim from San Francisco, which no other coyote has accomplished since the National Park Service took over management of the island in 1972. The animal, estimated to be about a year old, was panting and shivering, leaving those who saw it wondering whether it would survive. But to the surprise of staff and visitors alike, it was spotted again by another tourist, still alive and seemingly healthy. 

I’m standing with Joshua Winchell, the park’s chief of communications and special park uses, on the Agave Trail, which runs along the southern edge of the Parade Ground where the coyote was last photographed. An acrid odor wafts on the salty sea air as Winchell gingerly taps his foot on the grainy white substance covering the ground beneath our ranger-issued rubber boots. 

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“Guano,” he explains. “All of this is compacted bird poop, with maybe just a touch of actual dirt.”  

The coyote poses a predatory risk for the bird population on Alcatraz, in San Francisco Bay, on Jan. 29, 2026.

It’s typical of a rookery like this one, where bird colonies formed long before people ever visited and, without predators or human interference, have thrived in the decades since the closure of Alcatraz’s federal prison. Named “Isla de los Alcatraces” after the strange birds a Spanish........

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