Lauri Taylor from Salt Lake City, sent in this week’s Ask the Naturalist about a bird she spotted while visiting San Francisco:
I’m from out of state and recently visited SF and Baker’s Beach. I saw a brown/black sea bird — only one — that was either harried by the gulls or trying to steal food from them. It was smaller than the Western gull, fast and agile and could practically brake in mid-air to go another direction.
I thought the yellow on the beak and the black feet would help me identify it, but no luck so far. What the heck is this?
The bird Taylor spotted and featured in the above photo, is a young Heermann’s gull with a uniformly sooty brown body and yellow-colored bill, says naturalist David Wimpfheimer. More specifically, a first winter Heermann’s gull. Adult Heermann’s are distinguishable by their orange beak, sooty gray body and white feathering across their head and neck.
“This species of gull is unlike any other gull species in North America,” Wimpfheimer said. “They are one of the more dynamic water birds.”
Heermann’s gull, like many other gulls, is a known kleptoparasites meaning it frequently steals food from other birds. The brown pelican is often a victim, with adult Heermann’s gulls stealing food from adult pelicans and immature gulls stealing food from immature pelicans.
They are most common in California from the late summer to early fall, and spend the non-breeding season in North America. In the winter they largely retreat to Mexico to breed, said Alvaro Jaramillo, senior biologist at San Francisco Bay Bird Observatory.
David Wimpfheimer is a biologist and California naturalist.
Alvaro Jaramillo is a senior biologist at San Francisco Bay Bird Observatory.
Read Joe Eaton’s article to learn more about the dynamic gull species that inhabit the Bay.
A bird? A bug? Something strange in the natural world nearby? Ask us and we’ll find the answer!