Regulus calendula

Geographic Range

Ruby-crowned kinglets ( Regulus calendula ) are native to northern, western, and some eastern parts of North America. Their breeding range includes most of Alaska, the majority of Canada, a small portion of the Rocky Mountains, and the northern parts of the Great Lakes. Ruby-crowned kinglets live year-round in parts of the western United States and in the southwestern portion of Canada. Their winter range extends from the southeastern to western United States and dips south into Mexico and Central America. There are also two records of ruby-crowned kinglets in Greenland and another record from Iceland.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native

Habitat

Ruby-crowned kinglets live in a wide variety of habitats such as woodlands, thickets, scrub and open or edge habitats. In the east, they live in dense tree stands. In the west, they inhabit a wide variety of mixed and coniferous forests. During the spring and fall migrations, ruby-crowned kinglets inhabit a wide array of coniferous, deciduous, and floodplain forests with a shrubby understory, as well as suburban yards. In their winter range, they prefer a variety of low-laying lands and coniferous and deciduous forests. Likewise, during winter migration, they inhabit tropical riverside forests, semi-humid forests and woodlands, tropical semi-deciduous forests, and dry pine-oak forests in Central America and Mexico. They can be found from 450 to 3,000 m in elevation.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• taiga taiga
• savanna or grassland savanna or grassland
• chaparral chaparral
• forest forest
• scrub forest scrub forest
• mountains mountains

• Other Habitat Features
• suburban suburban
• riparian riparian

Physical Description

Ruby-crowned kinglets are olive-green and 9 to 11 cm from beak to tail. Adults typically weigh 5.0 to 9.7 grams and have a wingspan of 17 to 19 cm. Although both genders are similar in weight and length, sexual dichromatism does exist. Males have a scarlet patch on the crown of their head, in rare cases, the patch may be yellow, orange, or absent altogether. Their red patch is usually hidden, unless they become agitated and display it purposely. Females do not have a red patch. Ruby-crowned kinglets typically have 1,119 to 4,607 feathers. They have two white wing bars and a broken, white eye-ring. Their under parts are off-white, their lower back and upper tail coverts are olive-green with white bars on the middle of each feather, and their wing coverts are grayish with green edging and white tips. Their legs and feet are brown, paling to yellowish-brown near their toes. Their anisodactyl feet are suitable for perching. The bottoms of their feet are yellow with a hint of orange. Their bill is black-tinged brown, thin, and pointed. Their mouth lining is orange in adults and bright red in hatchlings. The iris of their eyes is dark brown. Juvenile ruby-crowned kinglets have brownish upper parts, with off-white wing bars. Juveniles do not have the red patch on their head; males gain it after their first summer. Ruby-crowned kinglets are most often confused with Hutton's vireos due to plumage similarities and the way they flick their wings. They differ in behavior; ruby-crowned kinglets are much more active in comparison to the relatively sluggish Hutton’s vireos.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes colored or patterned differently
• male more colorful

Reproduction

Courtship between ruby-crowned kinglets starts when a male approaches a female. The male hops from branch to branch around the female with his tail slightly raised and his red crown visible. The male sings and in response, the female flutters her wings. Then the male moves closer to the female and they disappear behind shrubbery to mate. Although ruby-crowned kinglets are monogamous, they have a new mate each year.

• Mating System
• monogamous monogamous

Kinglets usually raise one brood per year. During the first week of May, females generally choose a nesting site, carry nest materials, and build nests in about five days. Nesting trees average 16 m in height, but can range from 8 to 25 m. Nests are generally found at 12 m, but in some cases, the highest nests may be 24 to 27 m. Nests are protected by canopies and may blend in with the nesting tree's trunk. The outside of their nests are constructed from mosses, lichens, feathers, cocoon silk, spider webs, pieces of bark, twigs, roots, grasses, and conifer needles, while the lining is composed of feathers, fine grasses, plants, lichens, and animal fur. Their nests are somewhat elastic, allowing for expansion as the brood gets larger. Nests are usually 10 cm in diameter and 12 to 15 cm deep. Female ruby-crowned kinglets lay 5 to 11 eggs per brood per season. Their eggs appear nearly identical to those of golden-crowned kinglets , they are smooth, with a rounded oval shape and can be pure white or off white; they are also spotted with a brownish color and occasionally have a circle around the large end. Females lay eggs in about 8 to 12 days. The incubation period begins shortly after nest construction (late May to early June) and lasts 12 to 14 days. Females may start incubating before all of their eggs are laid. During incubation, the female buries herself in the nest and sits on top of her eggs. While incubating, females often groom themselves and take breaks by standing on a branch next to the nest. When ruby-crowned kinglets hatch in mid-June, they are altricial and parents begin feeding them immediately. They fledge about 12 to 19 days after hatching (typically early July); they become restless and energetic about a week beforehand. Young kinglets start vocalizing when they leave their nest. Both sexes reach sexual maturity after about 1 year.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• induced ovulation induced ovulation
• fertilization fertilization
• oviparous oviparous

Male ruby-crowned kinglets feed females during the incubation period, especially during cold weather. Females go to the nest's edge to receive food from males, and then return to the eggs. In warmer weather, females leave the nest for about five minutes at a time to collect food. Throughout the nestling stage, brooding is done by the female. Females move throughout the nest and are fed by the male after their young hatch. In the early stages of development, the male typically feeds the chicks by regurgitation, while the female broods. Both parents feed the young and keep the nest clean by removing fecal matter. In one study, a chick attempted to jump from the nest early, but the male pushed the chick back into the nest for safety.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • provisioning
    • male
    • female
  • protecting
    • male
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male

Lifespan/Longevity

The longest recorded lifespan for ruby-crowned kinglets is 5 years and 7 months in the wild. These birds are not typically kept in captive environments.

Behavior

Ruby-crowned kinglets spend their time flying, foraging, nesting, hopping, sleeping, and roosting. Of these activities, most of their time is spent foraging. They forage by hovering, gleaning, and hawking. They hover to glean insects, similar to golden-crowned kinglets . Kinglets glean by searching in trees and under leaves for insects. They hawk for food by flying to search for insects. They forage almost exclusively on twigs and branches and prefer taller trees. While they are foraging, they flick their wings continuously. When kinglets roost, they are generally alone on tree branches close to the trunk. Kinglets may exhibit aggressive behavior when a male faces a rival. During aggressive displays, males lean forward, with their red crown erect and visible and their rump high in the air, showing off the white bars on their tail. They flash their wings and turn from side to side while singing and moving their head from side to side slowly. In the winter, they react aggressively to Carolina chickadees , yellow-rumped warblers and orange-crowned warblers by chasing and occasionally attacking them. Ruby-crowned kinglets are more aggressive toward golden-crowned kinglets than towards conspecifics. Males migrate earlier in the spring than females, likewise, in the fall, females migrate earlier than males.

• Key Behaviors
• arboreal arboreal
• flies
• glides
• saltatorial saltatorial
• diurnal diurnal
• motile motile
• migratory migratory
• social social
• colonial colonial

Home Range

Ruby-crowned kinglets live in large territories of 1.1 to 6.0 hectares, which include their nests and their needed resources.

Communication and Perception

Ruby-crowned kinglets communicate primarily through vocalizations, such as songs and calls. There are four kinds of vocalizations. The first type is a song, which is mostly produced by males and includes a complex series of rather loud chattering and warbling notes. Their songs are mainly heard on breeding grounds, but may also be heard on wintering grounds and during spring migration. Their song is less variable in western populations than in eastern populations. The second type is an alarm call, which includes two variations. The third vocalization is a simple contact call, which is used to communicate with conspecifics. The final vocalization is the begging call, produced by chicks when they leave the nests; this is usually the first type of vocalization produced by the birds. When male kinglets communicate by displaying, they typically sing, whether they have a male audience or not. Males stand up straight and puff the feathers on their rump and crown; their red feathers are usually about 75% erect. When other males are present, they move as though they are performing a dance, moving side to side, with their rump and red crown puffed out. When faced with a rival, they supplement their display by flapping their wings and turning from side to side.

• Communication Channels
• visual visual
• acoustic acoustic

• Other Communication Modes
• choruses choruses

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Ruby-crowned kinglets primarily eat insects and spiders, but prefer flying prey. Their diet consists mainly of scale insects , mealy bugs , beetles , flies , wasps, ants , and moths . They also eat pseudoscorpions , some fruit, hardened seeds, and other vegetable matter, as well as various kinds of berries, such as elderberries and wax myrtle berries and they occasionally drink tree sap. Their diets change very little during the various seasons. During the winter and migration, they eat insects and their eggs, spiders and their eggs, hardened seeds, various fruit, and vegetable matter, although they do not consume vegetable matter during their breeding season.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
• omnivore omnivore

• Animal Foods
• eggs
• insects
• terrestrial non-insect arthropods

• Plant Foods
• seeds, grains, and nuts
• fruit
• sap or other plant fluids

Predation

Ruby-crowned kinglets have various predators such as large birds and small mammals. Their known predators include eastern-screech owls , sharp-shinned hawks , merlins , common grackles , gray jays , and red squirrels . In addition, gray jays are known to eat their eggs and red squirrels may destroy their nests. Ruby-crowned kinglets may also be harmed by the thorns of certain plants, such as greenbrier . Likewise, the sticky seeds of beggar's lice may attach to their feathers.

Ecosystem Roles

Ruby-crowned kinglets are known to carry ticks ( Ixodes dentatus and Haemaphysalis leporispalustris ), mites ( Proctophyllodes longiquadratus and Ptilonyssus acrocephali ), and hippoboscid flies ( Ornithomyia confluent ). Two parasite-borne diseases, avian malaria ( Leucocytozoon ) and encephalitis have also been found in kinglets. A study of brown-headed cowbirds revealed that ruby-crowned kinglets are rarely parasitized by this bird. Apparently, their small size and nesting habits deter this nest parasite. Brown-headed cowbirds are considerably larger than kinglets, and perhaps this difference is insurmountable for kinglets to effectively raise young cowbirds.

Economic Importance for Humans: Positive

Ruby-crowned kinglets help control pest populations. They eat insects, some of which are considered pests to humans. Kinglets also feed on invasive insect species, such as larch casebearers , which are considered a harmful species to certain plants.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

There are no known negative effects of ruby-crowned kinglets on humans.

Conservation Status

Ruby-crowned kinglets are listed as a species of least concern according to the IUCN Red List of Threatened Species, and are reportedly experiencing a population increase. Other sources document a slight decrease in the eastern North American population, but the cause for the decline is unknown. Ruby-crowned kinglets are negatively affected by the wildfires and logging that occurs in their habitats. One subspecies, Regulus calendula obscurus is likely extinct. This subspecies was known from a single island (Guadalupe Island in Mexico) and has not been seen in over 60 years.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Amanda Pendergrass (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Texas State University.

References

Alderfer, J. 2006. Complete Birds of North America . Washington, D.C.: National Geographic Society.

Arlott, N. 2011. Birds of North America and Greenland . Princeton, New Jersey: Princeton University Press.

BirdLife International, 2012. " Regulus calendula " (On-line). IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. Accessed November 25, 2013 at http://www.iucnredlist.org/details/22712567/0 .

De Magalhaes, J., J. Costa. 2009. A database of vertebrate longevity records and their relation to other life-history traits. Journal of Evolutionary Biology , 22: 1770-1774.

Farley, G. 1993. Observation of a ruby-crowned kinglet ( Regulus calendula ) roosting in a Verdin ( Auriparus flaviceps ) nest in winter. The Southwestern Naturalist , 38/1: 72-73.

Forsman, J., T. Martin. 2009. Habitat selection for parasite-free space by hosts of parasitic cowbirds. Oikos , 118/3: 464-470.

Franzreb, K. 1984. Foraging habits of ruby-crowned and golden-crowned kinglets in an Arizona Montane forest. The Condor , 86/2: 139-145.

Holt, W. 1942. Ruby-crowned kinglet as host of cowbird. The Auk , 59/4: 589.

Ingold, J., G. Wallace. 2008. Ruby-crowned kinglet. The Birds of North America Online , 119: None. Accessed September 09, 2013 at http://bna.birds.cornell.edu/bna/species/119/articles/introduction .

Keast, A., S. Saunders. 1991. Ecomorphology of the North American ruby-crowned ( Regulus calendula ) and golden-crowned ( R. satrapa ) kinglets. The Auk , 108/4: 880-888.

Klimkiewicz, M., R. Clapp, A. Futcher. 1983. Longevity records of North American birds: Remizidae through Parulinae . Journal of Field Ornithology , 54/3: 287-294.

Laurenzi, A., B. Anderson, R. Ohmart. 1982. Wintering biology of ruby-crowned kinglets in the lower Colorado River Valley. The Condor , 84/4: 385-398.

Lepthien, L., C. Bock. 1976. Winter abundance patterns of North American kinglets. The Wilson Bulletin , 88/3: 483-485.

McCurdy, D., D. Shutler, A. Mullie, M. Forbes. 1998. Sex-biased parasitism of avian hosts: Relations to blood parasite taxon and mating system. Oikos , 82/2: 303-312.

Pettingill, O. 1985. Ornithology in Laboratory and Field . London, England: Academic Press, Inc.

Päckert, M., J. Martens, J. Kosuch, A. Nazarenko, M. Veith. 2003. Phylogenetic signal in the song of crests and kinglets ( Aves : Regulus ). Evolution , 57/3: 616-629.

Rappole, J. 2006. A Guide to the Birds of the Southeastern States: Florida, Georgia, Alabama, and Mississippi . Gainesville, FL: University Press of Florida.

Sauer, J., J. Hines, J. Fallon. 2013. "The North American Breeding Bird Survey, Results and Analysis 1966-2005" (On-line). Accessed November 19, 2013 at http://www.mbr-pwrc.usgs.gov/bbs/ .

Shackelford, C., J. Shackelford. 2001. Ruby-crowned kinglet impaled on Greenbriar thorn. The Southwestern Naturalist , 26/1: 116-118.

Sloan, N., H. Coppel. 1968. Ecological implications of bird predators on the larch casebearer in Wisconsin. Journal of Economic Entomology , 61/4: 1067-1070.

Spicer, G. 1987. Prevalence and host-parasite list of some nasal mites from birds ( Acarina : Rhinonyssidae , Speleognathidae ). The Journal of Parasitology , 73/2: 259-264.

Sterry, P., B. Small. 2009. Birds of Eastern North America: A Photographic Guide . Princeton, New Jersey: Princeton University Press.

Swanson, D., E. Liknes, K. Dean. 1999. Differences in migratory timing and energetic condition among sex/age classes in migrant ruby-crowned kinglets. The Wilson Bulletin , 111/1: 61-69.

Terres, J. 1980. The Audubon Society Encyclopedia of North American Birds . New York: Alfred A. Knopf, Inc.

California Department of Fish and Game. California Wildlife Habitat Relationships System. B376. Sacramento, California: California Department of Fish and Game. 1988.