This spunky little finch is the smallest member of the North American genus Carduelis. I caught this male pictured above harassing a female Ruby-crowned Kinglet as she was bathing in the water feature.
Unlike the more common American Goldfinch, the Lesser Goldfinch’s (Spinus psaltria) plumage does not change color during breeding season. The male (seen below) has a black cap and, in Washington, Oregon, California, and Baja California, nearly all males have green backs. Eastward, frequency of individuals with black on auriculars, neck, and back increases; southward into Mexico, nearly all adult males have completely black upperparts1. Click on photos for full sized images.
This is their range map courtesy of NatureServe Explorer
The male also has bright yellow underparts.
The female Lesser Goldfinch can sometimes be confused with the female American Goldfinch in breeding plumage. This is the female Lesser Goldfinch…
and these are American Goldfinches in breeding plumage.
The orange beak on the female American Goldfinch and its white undertail coverts distinguish it from the female Lesser Goldfinch below, which has yellow undertail coverts and a darker beak.
Both of these species show gregarious flocking behavior except when nesting. I was lucky enough a few years ago to spot a Lesser Goldfinch building a nest in a nearby tree while checking my Bluebird boxes.
It was great fun watching them raise their young that summer. They always bring their youngsters to the feeders where, along with American Goldfinches and Pine Siskins, they not only make short order of sunflower and nyjer seed, they like to feed on sunflowers in the garden as well. You can hear the intricate call of the Lesser Goldfinch here.
References: 1Birds of North America Online