Editing Ruby-crowned kinglet (section)

===Vocalization===
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'' or ''tee-tee-tee''), two to five low trills (''turr'' or ''tu''), and a repeated three note "galloping" phrase (''tee-da-leet'', ''tee-da-leet'').<ref name="Borror">{{cite book |title=Songs of Eastern Birds|last=Borror|first=Donald J|year=1984|publisher=Dover Publications|location=[[Don Mills]]|isbn=978-0-486-99912-8|pages=44–45|url=https://books.google.com/books?id=dikA-15BLVEC&pg=PA44|access-date=3 November 2010}}</ref> 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, simple [[contact calls]], and begging calls produced by chicks.<ref name="BNA Voice">{{cite web|url=http://bna.birds.cornell.edu/bna/species/119/articles/sounds|title=Ruby-crowned Kinglet: Sounds|last1=Ingold|first1=J L|last2=Wallace|first2=G E|date=28 July 2008|work=The Birds of North America Online|publisher=Cornell Lab of Ornithology|access-date=3 November 2010}}</ref>

The subspecies ''C. c. grinnellii'', breeding from southeastern [[Alaska]] to [[British Columbia]] differs significantly from the nominate ''calendula'', 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.<ref name="Pyle">pp. 375–76 in {{cite book| last = Pyle | first = Peter | title = Identification Guide to North American Birds Part 1 | year = 1997 | publisher = Slate Creek Press | location = Bolinas, California | isbn = 978-0-9618940-2-3 | title-link = Identification Guide to North American Birds }}</ref>

The subspecies ''C. c. obscurus'', from [[Guadalupe Island]], off [[Baja California]], is considered endangered, and may already be extinct.<ref name = hbw>Martens, Jochen; Päckert, Martin "Family Regulidae (Kinglets & Firecrests)" pp. 330–349 in {{cite book| editor-last = del Hoyo | editor-first = Josep | editor2-last = Elliott | editor2-first = Andrew | editor3-last = Christie | editor3-first = David A. | title = Handbook of the Birds of the World Volume 11: Old World Flycatchers to Old World Warblers | year =2006 | publisher = [[Lynx Edicions]] | location = Barcelona | isbn = 978-84-96553-06-4 | title-link = Handbook of the Birds of the World }}</ref>

Hybridization with [[golden-crowned kinglet]]s has been reported to have possibly occurred.<ref name = "Pyle"/>