The white-throated magpie-jay is a large blue, black and white corvid. Its name is derived from the long blue, white-tipped tail, reminscent of that of a magpie. Blue above and white below, the species has a black necklace, variable black patterning on the face, and a curling black plume originating just above the nares.
The white-throated magpie-jays is most similar in appearance to its close relative, the black-throated magpie-jay (Calocitta colliei). The two overlap only in a narrow zone in west-central Mexico, but they can be told apart readily by two features.
First, the central retrices of the tail of the black-throated magpie-jay are highly elongated and somewhat floppy at their tips, resulting in a streamer-tailed appearance when flying. Secondly, as the names suggest, white-throated magpie-jays have a white throat bordered by a black necklace, while black-throated magpie-jays have an entirely black throat and a bluish or whitish triangle extending along the malar stripe. Hybrids in the contact zone have been described.
Generally, both sexes are similar, but some minor sex differences exist in C. f. pompatus (Langen 1998). Some geographic variation across described subspecies.
Both sexes: Bill, eyes, and legs black. Wings light grey-blue, upper-tail coverts, back and nape more vibrant light blue. Central two pairs of retrices similar blue and very long, outer retrices dark above, black below, with long white tips, grading in size to form a deep diamond or wedge-shaped tail when spread, blue with white tips above. Belly and undertail coverts white, throat white, chest crossed by black necklace. Black from necklace runs up sides of neck, forming a black border separating white throat and cheeks from blue nape. Auriculars also white with small black patch beneath. Cheeks white, often with a very light blue cast.
Age and Sex Differences: Age and sex seem to interact to influence pluamge in magpie-jays, at least in Costa Rican populations. Young birds (fledglings) of both sexes (?) may lack black borders on the neck and may have an entirely white nape. As both sexes age, black becomes a more prominent part of the facial plumage, but older females tend to become much darker than older males. Adult males may have bi- or tri-colored crests, white at the base and tipped with black, or blue and black in some cases. They also tend to have white nares and eyebrows. Older males may have noticeable black borders on the neck, but younger males may lack this, and have an incomplete black necklace. Adult females tend to have entirely black crests, nares, and mostly black eyebrows, though they often have a white or blue patch above the eye. Older females may have more prominent black borders on the neck, and thicker necklace, and a larger ear-patch.
No comprehensive information on molts. Three multi-year studies only focused on nesting period (February-July). Early during the breeding period some males observed molting out tattered central retrices, but little evidence of wing-molt from banding during this period.
Bill black. Eyes black. Legs black.
Adults of C. f. pompata in Guanacaste, Costa Rica, ranged from 183g-219g (mean 199g) in weight.
The tail, which is sexually dimorphic, ranges from 17.5cm to 19.7cm (mean 18.6cm). Tarsus averages 45.4mm (42.8-53.1). Culmen length averges 32.3mm, width 11.9mm, and depth, 13.7mm. Wing chord averages 18.7cm (17.0-19.7cm). Crest length is variable, averaging 6.7cm, but ranging from 5.0cm to 8.5cm.