One of the cool things about visiting California in January was seeing hummingbirds in the winter. On field trips near Chico I saw Anna's hummingbirds flash their red faces in the sun.
Anna's hummingbird (Calypte anna) is found year round in many parts of California. The rainy season triggers breeding so they nest from December to May. Though there's snow on the mountains in January, the manzanita that blooms at lower elevations attracts these tiny birds.
Often an Anna's will stake out a bush, watching and waiting to chase off other hummingbirds. His forehead, face and gorget flash a warning red, "This is mine! Stay away!"
The video from Cornell Lab shows how flashy this hummingbird can be.
(video about iridescence from Cornell Lab of Ornithology)