- 3.5–4.3 in
- 6.3–7.1 in
- 0.2–0.4 oz
- Roitelet à couronne rubis (French)
- Reyezuelo de Rojo, Reyezuelo Monicolorado, Reyezuelo de Coronilla Colorado, Reyezuelo (Spanish)
- The Ruby-crowned Kinglet is a tiny bird that lays a very large clutch of eggs. Although the eggs themselves weigh only 0.65 g (0.02 oz), an entire clutch can weigh as much as the female herself.
Though Ruby-Crowned Kinglets are most often found in spruce-fir forests in the northwestern United States and Canada, they also live in mixed woods, in isolated trees in meadows, in coniferous and deciduous forests, in mountain-shrub habitat, or in floodplain forests of oak, pine, spruce or aspen. These birds nest high in trees, and so prefer older, taller, and denser stands to younger ones.
Ruby-Crowned Kinglets prey on spiders, pseudoscorpions, and many types of insects, including aphids, wasps, ants, and bark beetles. Kinglets usually forage in high tree foliage, hovering and pecking in order to glean insects from the surface of leaves and branches. These birds also eat a small amount of seeds and fruit, from poison-oak berries to the pulp of dogwood berries.
- Clutch Size
- 5–12 eggs
- Number of Broods
- 1 broods
- Egg Length
- 0.5–0.6 in
- Egg Width
- 0.4–0.5 in
- Incubation Period
- 12–14 days
- Nestling Period
- 16–18 days
- Egg Description
- Drab white spotted with red-brown around large end.
- Condition at Hatching
- Helpless and completely naked, without any down.
It takes Ruby-Crowned Kinglet females five days to build their nests, making trips every five minutes or so to gather materials: grasses, feathers, mosses, spiderwebs and cocoon silk for the outer structure, fine plant material and fur for the inner lining. When completed, the globe-shaped nest is 4 inches wide and 5-6 inches deep, and requires regular maintenance to keep it from disintegrating. Inside, it's about 3 inches across and 2 inches deep. The nest is elastic enough that it can stretch as the brood grows.
Ruby-Crowned Kinglets make their nests in trees, occasionally as high up as 100 feet. Females choose a nest site near the tree trunk or suspended from small twigs and branchlets. Because of the nest site's height and often remote location, not much is known about kinglet nesting habits. Their nest sites, chosen by the females, are protected and often hidden by overhanging foliage.
Breeding pairs of Ruby-Crowned Kinglets stay together for two months, until their chicks fledge. Ruby-Crowned Kinglets use their long, bubbly, and amazingly loud songs to establish territories; this is more energy efficient than chasing and less dangerous than fighting. They can be recognized by a constant flicking of their wings.
Despite how commonly Ruby-crowned Kinglets can be seen, they show modest population declines in eastern North America since 1966. Their populations are on the rise in western North America. Kinglets seem to handle human disturbance and habitat fragmentation fairly well, though logging and wildfire may reduce their numbers. Their wide use of habitats in winter helps them tolerate human disturbances.
- Ingold, J. L., and G. E. Wallace. 1994. Ruby-crowned Kinglet (Regulus calendula). In The Birds of North America, No. 119 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D.C.