| Ruby-crowned kinglet | |
|---|---|
 | |
| Male in Réserve naturelle du Marais-Léon-Provancher, Québec, Canada | |
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| Adult in New York, USA | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Regulidae |
| Genus: | Corthylio Cabanis, 1853 |
| Species: | C. calendula |
| Binomial name | |
| Corthylio calendula (Linnaeus, 1766) | |
 | |
| Range ofC. calendula Year round Summer (breeding) Winter (nonbreeding) Migration (ranges are approximate) | |
| Synonyms | |
Regulus calendulaLinnaeus, 1766 | |
Theruby-crowned kinglet (Corthylio calendula) is a very smallpasserine bird found throughoutNorth America. It is a member of thekinglet family. The bird has olive-green plumage with two white wing bars and a white eye-ring. Males have a red crown patch, which is often concealed. The sexes are identical apart from the crown, and juveniles are similar in plumage to adult females. It is one of the smallest songbirds in North America. The ruby-crowned kinglet is not closely related to other kinglets and was moved fromRegulus to its owngenus,Corthylio in 2021.[2] Threesubspecies are currently recognized.
The kinglet is mostly migratory, and its range extends from northwest Canada and Alaska south to Mexico. Its breeding habitat isspruce-fir forests in the northern andmountainous regions of the United States and Canada. The ruby-crowned kinglet builds a cup-shapednest, which may be pensile or placed on a tree branch and is often hidden. It lays up to 12 eggs, and has the largest clutch of any North American passerine for its size. It is mainlyinsectivorous, but also eats fruits and seeds.
The ruby-crowned kinglet wasformally described in 1766 by the Swedish naturalistCarl Linnaeus in thetwelfth edition of hisSystema Naturae under thebinomial nameMotacilla calendula.[3] Linnaeus based his description on "The Ruby-crowned wren" that had been described and illustrated in 1758 by English naturalistGeorge Edwards in hisGleanings of Natural History. Edwards had received dried specimens sent by the American naturalistWilliam Bartram from Pennsylvania.[4] The French zoologistMathurin Jacques Brisson in 1760 had also published a description based on Edwards and had coined the Latin nameCalendula Pensilvanica.[5] Although Brisson coined Latin names, these do not conform to thebinomial system and are not recognised by theInternational Commission on Zoological Nomenclature.[6] Linnaeus specified thelocality as Pennsylvania but this is now restricted toPhiladelphia.[7]
The kinglets are a small group of birds formerly included in theOld World warblers, but now given family status,[8] especially as recent research showed that, despite superficial similarities, the crests are taxonomically remote from the warblers.[9][10]
The ruby-crowned kinglet was formerly placed in the genus Regulus. As a result of its larger size, strongly red (rather than orange or yellow) crest and lack of black crown stripes, as well as its distinctive vocalizations, the ruby-crowned kinglet is considered different enough from the Old World kinglets and the other American species, the golden-crowned kinglet, to be assigned to a separate genus,Corthylio, that was introduced in 1853 by the German ornithologistJean Cabanis.[11][2][12] The genus name is from theAncient Greekkorthúlos, a small wren-like bird mentioned by the Greek lexicographerHesychius of Alexandria.[13] Phylogenetic evidence indicates that the ruby-crowned kinglet's lineage diverged from the rest ofRegulus during the mid- to lateMiocene, about 10–15 million years ago.[14]
Up to fivesubspecies have been described, but "C. c. cineraceus", breeding inmontane westernNorth America, and "C. c. arizonensis", breeding inArizona, are considered to be clinal variants of the nominate subspecies.
The three subspecies are:[12]
The ruby-crowned kinglet is a very small bird, being 9 to 11 cm (3.5 to 4.3 in) long, having a wingspan of 16 to 18 cm (6.3 to 7.1 in), and weighing 5 to 10 g (0.2 to 0.4 oz).[17] It has gray-green upperparts and olive-buff underparts.[18] It has two white wingbars and a broken white eye ring. The wingbar on the greater secondary coverts (closer to the wing-tip) is wider, and is next to a dark band. The kinglet has a relatively plain face and head, although the male has a scarlet-red crown patch, which is usually concealed by the surrounding feathers. The crown patch is rarely orange, yellow, or not present.[19] Females are identical to males (except for the crown). Immature birds are similar to adult females, since young males lack a crown patch.[18] The kinglet usually moves along branches or through foliage with short hops, and flies with bursts of rapid wing beats. It is constantly active, and is easily recognized by its characteristic wing-flicking. Its flight has been described as "swift, jerky, and erratic".[20]
Compared to the relatedgolden-crowned kinglet, the ruby-crowned kinglet is slightly larger, more elongated,[21] and has greener plumage. The bird can be mistaken forHutton's vireo, which also displays wing-flicking, though less frequently than the kinglet. It can also be mistaken for thedwarf vireo in Mexico. However, both of the vireos are larger, have stouter bills and legs, and lack the kinglet's black bar on the wings.[19]
The ruby-crowned kinglet's vocalizations are remarkably loud and complex for its size. Its song can be divided into three main parts: a series of high pitched notes (zee-zee-zee ortee-tee-tee), two to five low trills (turr ortu), and a repeated three note "galloping" phrase (tee-da-leet,tee-da-leet).[22] However, there is variation in the songs of a given individual, and they often contain only one or two of the three parts. The third part is only sung by male birds; an abbreviated version is heard from the females. Other vocalizations of the ruby-crowned kinglet include alarm calls, simplecontact calls, and begging calls produced by chicks.[23]
The subspeciesC. c. grinnellii, breeding from southeasternAlaska toBritish Columbia differs significantly from the nominatecalendula, and so is considered to represent a valid subspecies: it is smaller and shorter-winged, its upperparts are darker and greener, its underparts are buffy rather than grayish-olive, and the vent is tinged yellow rather than dull whitish-olive.[24]
The subspeciesC. c. obscurus, fromGuadalupe Island, offBaja California, is considered endangered, and may already be extinct.[25]
Hybridization withgolden-crowned kinglets has been reported to have possibly occurred.[24]
Their breeding habitat isconiferous forests acrossCanada,Alaska, northernNew England and the western United States. They nest in a well-concealed hanging cup suspended from a conifer branch and may lay as many as twelve eggs in a clutch.
The recent counting indicates that the ruby-crowned kinglet population is on the rise. This is mainly due to discovery of less disturbed territory farther north. This allows more successful breeding.
These birdsmigrate to the southern United States andMexico. Some birds are permanent residents in the west.
Ruby-crowned kinglets forage actively in trees or shrubs, mainly eating small insects andspiders, some berries and treesap. They may hover over a branch while feeding and sometimes fly out to catch insects in flight. The red crest is raised when agitated or in display. Often, they perform a "broken-wing" act to draw predators away from their nest, which they will defend fearlessly,mobbing the intruder which may be a cat, squirrel, or human.
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