Chestnut-collared Longspur, Calcarius ornatus
Chestnut-collared Longspurs nest in short-grass prairie in the Great Plains of Canada and the northern United States and southern Canada; they winter in similar habitat in the southwest of the US and northern Mexico, including southeastern California. A few each year are found wintering in the northern half of California, including this bird, a female, probably first-cycle, seen by many SF Bay Area birders in late 2018 among flocks of wintering American Pipits in the large short grass and dirt field at the southern end of Shoreline Park in Mountain View, Santa Clara County. This was my first photo of a Chestnut-collared Longspur; I had seen the colorful breeding males of the species on a spring trip to North Dakota in 1999, before I took up bird photography, and had photographed similarly colorful males of the closely related Lapland Longspur near Nome, Alaska, in 2011.
The same bird foraging for seeds, their primary food, in the short-grass habitat favored by the species. They prefer grass kept low by grazing, originally bison. Loss of favored habitat has severely impacted this species.