This is an immature female representing the first county record for San Francisco. Identified as female by lack of black mottling on chest, crown feathers buffy with dark shaft streaks, and median coverts light buff lacking rusty tips. Note the long primary projection with four primaries visible past the folded tertials. This helps distinguish McCown's from the similar Chestnut-collared Longspur (Calcarius ornatus).
McCown's is a shortgrass prairie specialist which has declined by an estimated 88% from 1966-2014 according to the North American Breeding Bird Survey. Conversion of prairie habitat to agriculture has contributed to this decline. This unique species is more closely related to the Snow Bunting than to other longspurs. It is the sole member of the genus Rhynchophane characterized by its peculiar bill shape (heavy lower mandible) and shorter rear claw.
Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter).
References:
Pyle, P. 1997. Identification guide to North American birds Part I: Columbidae to Ploceidae. Bolinas, CA: Slate Creek Press.
With, Kimberly A. 2010. McCown's Longspur (Rhynchophanes mccownii), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. https://doi.org/10.2173/bna.96