Original description: Zonotrichia mystacalis Hartlaub 1852
Taxonomic history in AOU/AOS Check-list
AOU 6 (1983): Bridled Sparrow, Aimophila mystacalis
AOU 7 (1998): Bridled Sparrow, Aimophila mystacalis
IUCN Conservation Status: Of least concern
Behavior: Timid and retiring, Bridled Sparrows disappear into dense vegetation when startled by an observer. They feed individually or in pairs or small family groups, hopping through the dense grasses beneath shrubs or hunting slowly and methodically along the lower branches of trees and shrubs. This species is also known to hover at the tips of low branches to pluck food from the foliage or to take nectar from flowers. The long tail and exceptionally long tarsus may improve the bird’s maneuverability when hunting in among twigs.
Males sing from a prominent exposed perch.
Voice: The primary song of the male Bridled Sparrow begins with a short, sharp note, followed by a squeaky pitchew and a liquid tremolo. There is also a “chatter duet” given by both members of a pair when they are reunited after a separation; this twittering vocalization comprises ten or more scratchy notes at slightly different pitches and in an irregular rhythm. Other calls include a loud, rich dzip and a short, sharp alarm note.
Detailed description and measurements drawn from standard reference works
Adult: Tail feathers dusky with narrow lighter edges. Upper tail coverts and rump rusty cinnamon. Back brown with black streaks; scapulars bright rusty. Primaries, secondaries, and tertials dull black with lighter edges. Greater and median coverts with white tips, forming parallel wing bars. Nape grayish with light dusky streaking.
Under tail coverts and vent buffy cinnamon. Breast and belly dull white. Flanks and sides of breast buffy. Throat black, sometimes with white flecking, and chin usually white; jaw stripe white.
Crown grayish with short dusky streaks, forehead with short narrow white stripe or spot. Ear coverts grayish, bordered below by darker grayish whisker and above by narrow, faint darker grayish eye line. White eye ring broken behind and in front of eye. Lore blackish, oblong white spot above lore.
Tarsus and toes light brownish pink. Bill black above, dull blue below.
Juvenile: Tail feathers dusky with narrow lighter edges. Upper tail coverts and rump rusty cinnamon. Back brown with blackish streaks; scapulars brighter brown. Primaries, secondaries, and tertials dull black with lighter edges. Greater and median coverts with buffy edges and tips, forming parallel wing bars. Nape grayish brown with light dusky streaking.
Under tail coverts and vent buffy. Breast and belly dull white with heavy brown streaks. Flanks and sides of breast brown. Throat whitish with dusky spots, dark brown or blackish lateral throat stripe. Jaw stripe buffy yellowish.
Crown grayish with short dusky streaks, forehead with short narrow yellowish stripe or spot. Ear coverts grayish, bordered below by darker grayish whisker and above by narrow, faint darker grayish eye line and buffy grayish supercilium. Eye ring broken behind and in front. Lore blackish, oblong yellowish spot above lore.
Tarsus and toes light brownish pink. Bill black above, dull blue below.
Length 142-160 mm (5.6-6.3 inches)
Wing 62-73 mm (2.4-2.9 inches)
Tail 69-81 mm (2.7-3.2 inches)
W:T 0.89
Mass 19-26 g
