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Last week, the serviceberry bushes by our home were buzzing with royal activity. Kinglets of both local species were flitting and hovering, gleaning the insects from the leaves of the bush. This gave me a golden and ruby opportunity to compare the field markings of these two diminutive birds.

The kinglets are some of our smallest birds. The Ruby-crowned (Regulus calendula) measures only 4.25 inches and weighs about one-quarter of an ounce. The Golden-crowned (Regulus satrapa) is even smaller; it is 3.25 to 4.00 inches long and weighs about a fifth of an ounce. Both species are olive green above and have yellow edging on the flight feathers. The underparts are dusky white. During spring they are grayer and less yellowish than during autumn. They have two bold white wing bars and the lower wing bar has black below the inner half. Their eyes and short bills are black, and their legs are dark with yellow feet. Both species feed by gleaning insects from leaves and tips of branches. Kinglets flick their wings constantly, as often as once per second. They both hover like hummingbirds but Golden-crowned will often be seen hanging upside down while they are feeding. They can accomplish this acrobatic maneuver because their feet have grooved soles, which give them clinging power.

Side by side, the two species of North American Kinglets are easy to distinguish. The Golden-crowned Kinglet has a bold black and white striped facial pattern and gold crown patch compared to the plain facial pattern and broken bold eye ring of the Ruby-crowned. The red crown patch of the Ruby-crowned is only visible in the male and will only be displayed when he is agitated. The crown patch of the Golden-crowned is apparent at all times in both sexes; the male exhibits a brighter orange than the female. The gold crown patch gives it its Latin name Satrapa, meaning a ruler wearing a golden crown.

The Ruby-crowned Kinglets feeding here on the serviceberry bushes in August most likely bred here. They will be joined in the early fall by others who have bred in Canada and Alaska on their way south. Ruby-crowneds can breed farther north (almost to the north coast of Alaska) than the Golden-crowned Kinglets, but they are apparently less hardy and so migrate earlier and winter farther south. Winter range is closely related to temperature; they travel as far south as Guatemala and avoid areas where the temperature frequently drops below 25 degrees Fahrenheit. There is an altitudinal as well as longitudinal migration in the Rocky Mountains, as birds retreat from high-altitude breeding areas. Most wintering birds are found west of the mountains.
Ruby-crowned Kinglet populations can fluctuate widely, declining in response to logging activities or fire, but severe winter weather appears to have the greatest effect on numbers. Male kinglets apparently winter farther north than females. Perhaps that makes it easier for them to rush back up here in early spring to claim their territory and treat us all to their distinct song of early spring: tsee-tsee-tsee churr churr churr tee-da-leet tee-da-leet, tee-da-leet. The song is usually sung from the upper branches of a spruce tree by males defending their territory. I recognized this song as a harbinger of spring long before I learned the identification of the tiny bird that produced this loud rollicking melody. Females may also sing, but their song is shorter and, as would be expected, sung with less machismo.

The Golden-crowned Kinglets that visited us this month might be encountered here again this winter. We find them commonly on the Christmas Bird Counts; Bigfork Bird Count has recently recorded as many as 150 individuals. Golden-crowned Kinglets nest in northern conifer forests and prefer to winter in conifers as well. They are tiny birds, second only to hummingbirds. How they can survive our frosty winters is remarkable. One of their survival strategies seems to be constant foraging during the day. Golden-crowned Kinglets are important predators on insect larvae and eggs; insect foods consist of budworms, aphids, bark beetles, scale insects and others. These insectivorous birds have been shown to consume 84% of budworm larvae and pupae in early stages of a budworm outbreak, illustrating one of the economic benefits they bestow to the forests they inhabit. Although their food consists primarily of insects, their diet also includes some tree sap. To survive cold winter nights they roost together, often in tree cavities, to retain body heat.
Based on the Breeding Bird Survey database, Golden-crowned Kinglets are one of seven species whose populations declined significantly from 1968 to 1991. As with Red-breasted Nuthatch, Brown Creeper, and Mountain Chickadee, this is a species which is impacted significantly by removal of mature trees from the environment.

When spring arrives, the song of the Golden-crowned is much harder to detect than that of the Ruby-crowned; it is soft and high pitched and consists of about a dozen ascending notes sometimes combined with a warbled ending. The call is easier to detect; it consists of one to five notes on a single high pitch: zeee, zeee, zeee.

The serviceberry bushes will be bare of leaves in a couple of months and the kinglets will have moved on to more promising hunting grounds. The bushes certainly provided a good opportunity for kinglet viewing and when it is time to plant more shrubs next spring, native serviceberry bushes will be on the top of my list.