Anna's Hummingbirds are, of course, small birds (3.9 to 4.3 inches/10-11 cm long). The males have iridescent light crimson crown, and bronze-green and grey plumage. Some outer feathers have white tips. The females and juveniles lack the iridescent crown, instead having a dull green crown. They have some red markings along their grey throats.1 All have iridescent bronze-green plumage on their backs.
Some people confuse the male Anna's Hummingbird with the better known Ruby-throated Hummingbird due to their very similarly coloured plumage.
Male Anna's are very territorial, attacking larger birds (including geese and eagles) that pass through it's territory. (A male Anna's was once found dead by a hunter, tangled in the feathers of the Canada Goose it had attacked.) They will divebomb people and other hummingbirds who are near their primary food source, making a "booming" sound with their tail feathers as they do to drive them off. They also make this noise during their mating ritual, in which they will fly up to 130 m in the air and dive straight down.
Anna's Hummingbirds eat nectar, flying insects, and spiders, and have been seen to consume tree sap on occasion.
A squeaky, high pitched looping "bzz bzz, bzz bzz, bzz bzz, bweee" call is a variant of their primary call.2
Anna's tend to live along the Pacific coast of North America, from British Columbia down to Arizona.