The Ruby-crowned Kinglet is a small songbird native to North America. Its scientific name is Regulus calendula. Regulus is Latin for “little king” and refers to the tiny size and bright crest of this bird. Calendula means “little calendar” in Latin and refers to the brightly colored crown that resembles a red dot on the calendar.
Overview of the Ruby-crowned Kinglet
The Ruby-crowned Kinglet is one of the smallest songbirds in North America, measuring only 4-5 inches in length and weighing 5-10 grams. It has olive-green plumage on its back and wings, with white underparts and two bold white wingbars. The male has a brilliant red crown patch in the center of its head that is usually concealed. When alarmed or excited, the male raises its crown feathers to reveal the bright red patch. This distinctive ruby-red crown gives the bird its common name.
The Ruby-crowned Kinglet breeds across Canada and the northern United States. It migrates south to the southern U.S. and Mexico for the winter. Its preferred habitat is coniferous forests. It forages actively among the trees, searching for insects and spiders to eat.
These tiny songbirds are masters of flight and can hover and fly backwards as they pick insects off branches and leaves. Their call is a high-pitched, squeaky series of notes. The male’s song is a melodic series of whistles and trills.
Taxonomy and Classification
The Ruby-crowned Kinglet belongs to the following scientific classification:
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Regulidae
Genus: Regulus
Species: Regulus calendula
Regulidae is a family of small passerine birds that contains the kinglets. The genus Regulus has four other closely related species in addition to the Ruby-crowned Kinglet:
- Golden-crowned Kinglet (Regulus satrapa)
- Madeira Firecrest (Regulus madeirensis)
- Common Firecrest (Regulus ignicapilla)
- Goldcrest (Regulus regulus)
Etymology and Naming
The genus name Regulus is from the Latin word meaning “little king” or prince, referring to the colored crest sported by the kinglets that resembles a crown.
The species name calendula means “little calendar” in Latin and refers to the resemblance of the male’s red crown patch to a red dot on the calendar.
The common name “Ruby-crowned Kinglet” refers to the brilliant red crown patch of the male. “Kinglet” denotes the bird’s diminutive size yet regal crest.
Other Common Names
Some other common names for the Ruby-crowned Kinglet include:
- Ruby-crowned Wren
- Ruby-crested Wren
- Ruby-crowned Warbler
- Flame-colored Wren
These names highlight the ruby-red crown patch of the male or the bird’s small size. Regional names include Petit Roi (“little king” in French) and Chinito Coronado (“crowned little one” in Spanish).
Identification
Identifying the Ruby-crowned Kinglet is straightforward due to its distinctive features:
- Very small size, about 4-5 inches long and 5-10 grams in weight
- Olive-green upperparts and wings
- Pale yellow underparts
- Two bold white wingbars
- Male has a red crown patch usually concealed but raises when agitated
- Constantly active forager, hovers and flies backwards to pick insects off foliage
- High-pitched, squeaky call and melodic song
The kinglet’s tiny size, olive-green and yellow plumage, white wingbars, and tendency to keep its red crown concealed makes it a challenging bird for beginners to identify. It takes patience and a sharp eye. TheCallNote Birding blog recommends looking for their constant movement as they hop and hover through branches.
The Ruby-crowned Kinglet could potentially be confused with the female Verdin or Hutton’s Vireo. But the vireos lack wingbars and do not have the kinglet’s hovering, acrobatic foraging style. Females and immatures can be harder to differentiate, so try to get a look at the concealed crown patch.
Habitat
The Ruby-crowned Kinglet breeding habitat consists of mature coniferous or mixed forests across Canada, Alaska, the Northeastern and Western United States, and mountainous areas of the Western and Eastern regions.
They prefer habitats with a dense, multi-layered canopy structure interspersed with open space for feeding. Specific forest types include:
- Pine forests
- Fir forests
- Spruce forests
- Cedar forests
- Redwood forests
- Aspen groves
In winter, they expand their habitat preferences to a broader range of woodlands and shrublands with some trees or tall shrubs:
- Deciduous trees
- Joshua tree woodlands
- Mesquite bosques
- Oak-juniper woodlands
They mainly occupy higher canopy levels in the breeding season and mid-canopy levels in winter. You can often find them near water features.
Range and Distribution
Breeding Range
The Ruby-crowned Kinglet breeding habitat spans:
- Across Canada
- Alaska
- Northeastern states
- Great Lakes region
- Rocky Mountains
- West Coast states
- Pacific Northwest
They breed mainly in coniferous mountain forests. The highest densities occur along the West Coast and in the Cascade, Sierra Nevada, and Rocky Mountain ranges.
Winter Range
In winter, the Ruby-crowned Kinglet migrates across the southern U.S. into:
- California
- Arizona
- New Mexico
- Texas
- Gulf Coast states
- Mexico
They occupy a broader range of open, mixed woodlands and scrublands in winter. Their abundance increases along the California coast and desert southwest.
Migration
Ruby-crowned Kinglets migrate at night in mixed flocks with other songbirds. Spring migration takes place from mid-March to May. They arrive on breeding grounds by May or June.
Fall migration is earlier, running from September to early November. They start arriving on winter grounds by late September.
Behavior and Diet
Foraging Behavior
The Ruby-crowned Kinglet is constantly in motion as it searches for food. It forages actively among branches and foliage, almost never stopping.
Unique foraging behaviors include:
- Hops quickly from branch to branch
- Hovers and gleans insects from leaves
- Hangs upside down to probe under branches
- Flys backward to pick insects off leaves
- Joins mixed-species foraging flocks in winter
Their fast, acrobatic movements allow them to grab tiny insects and spiders other birds can’t reach. They stay on the move throughout harsh winters when food is scarce.
Diet
The kinglet is primarily insectivorous, feeding on:
- Spiders
- Aphids
- Caterpillars
- Beetles
- Ants
- Moth and butterfly eggs
- Some berries and tree sap in winter
Their tiny beaks allow them to pluck minute insects and eggs from foliage and crevices. They eat beetles and moth eggs other birds find unpalatable.
Social Behavior
Ruby-crowned Kinglets are solitary in the breeding season. They migrate in loose flocks and may join multi-species foraging flocks in winter for greater protection.
They become more social in winter months, aggregating in larger flocks up to 100+ birds. Loose flocks may optionally merge and split off.
Vocalizations
Ruby-crowned Kinglets produce high-pitched squeaks and whistles. Their common calls include:
- Call note – High, thin “tsee” whistle, often repeated rapidly
- Song – Series of 10-25 notes increasing in speed. Includes warbles, trills, and terminating in a scratchy jumble of notes.
- Alarm call – Harsh, raspy “dzee-dzee-dzee” when alarmed
The male primarily sings during breeding season to establish territory and attract females. Both sexes communicate year-round with call notes while foraging and moving in flocks. Their soft, high-pitched vocalizations can be tricky to detect.
Reproduction and Nesting
Courtship
In spring, returning males establish breeding territories and sing complex songs to attract females. Males display their bright crown patch prominently during courtship.
Courtship feeding of the female also occurs, with the male offering food gifts. Pairs form quickly and may stay together for more than one breeding season.
Nest Site
Female Ruby-crowned Kinglets build an open, cup-shaped nest out of mosses, lichens, bark strips, spiderwebs, and feathers. Nest sites include:
- Conifer tree branches
- Deciduous shrubs
- Tree stumps
- Low vegetation
Nests are well-hidden, only about 3-5 inches wide and placed 6-15 feet off the ground. The inner cup is neatly formed and secured with spider silk.
Eggs
Females lay 5-12 creamy white eggs with brown speckles. The eggs measure only 0.5 inches long.
Incubation lasts 12-15 days. Only the female incubates the eggs. She develops a brood patch with increased blood flow to keep the eggs warm.
Young Birds
Both parents feed the hatchlings, which fledge the nest at 15-17 days old. Fledglings follow the parents and beg loudly for food.
First year mortality is high. Adults that survive may breed for several seasons. The oldest recorded Ruby-crowned Kinglet lived to over 7 years.
Conservation Status
The Ruby-crowned Kinglet has an extensive breeding range estimated at 5.1 million square kilometers. Its global population is estimated at 19 million individuals.
The IUCN Red List categorizes it as a species of Least Concern. Its numbers are stable and may be increasing in some regions.
Specific conservation threats include:
- Habitat loss from logging and development
- Increased nest predation from human changes to forests
- Drought and severe weather
- Climate change disrupting migration and breeding cycles
Protecting mature, contiguous forest habitats will benefit Ruby-crowned Kinglets. Conservation efforts should focus on mitigating habitat fragmentation and maintaining suitable nesting sites.
Significance to Humans
The active, acrobatic Ruby-crowned Kinglet provides important ecosystem services:
- Consumes many tiny forest pest insects
- Disperses seeds and pollinates flowers
- Controls insect populations as a natural biocontrol
- Provides aesthetic value for birdwatchers with its stunning plumage and energetic movements
This tiny songbird punches above its weight class in consuming pest insects and spiders other birds ignore. Monitoring kinglet populations and movements provides insight into the overall health of the coniferous forests they inhabit.
Conclusion
In summary, Regulus calendula is the scientific name denoting the Ruby-crowned Kinglet, one of North America’s smallest and most energetic songbirds. Its Latin genus Regulus means “little king,” referring to its diminutive size and colorful crest. The species name calendula compares its red crown patch to a red dot on the calendar.
This feisty bird punches above its weight class, consuming pest insects in vast quantities and controlling forest insect populations. Its acrobatic foraging style allows it to hunt tiny insects other birds can’t reach. Though small, the Ruby-crowned Kinglet provides outsize ecological services for the health of coniferous forests across its range. Protecting mature, contiguous forests will benefit these tiny but mighty birds into the future.