Birds of America
By John James Audubon, F. R. SS. L. & E.
GENUS II.--SIALIA, Swains. BLUE-BIRD.
Bill of ordinary length, nearly straight, broader than high at the base,
compressed toward the end; upper mandible with the dorsal line straight and
slightly declinate, until near the end, when it becomes convex, the ridge
narrow, the sides convex toward the end, the edges overlapping, with a distinct
notch close to the narrow deflected tip; lower mandible with the angle of
moderate length, and narrow, the dorsal line straight, the sides convex, the
edges direct, the tip narrow. Nostrils basal, oval. Head rather large, ovate,
neck short; body moderately full. Feet of ordinary length, rather slender;
tarsus shorter than the middle toe and claw, its lower scutella only distinct;
toes of moderate length, the first stouter, the lateral equal, the third much
longer; the fourth adherent at the base; claws moderate, well curved,
compressed, laterally grooved, acute. Plumage soft and blended; short bristles
at the base of the upper mandible. Wings very long, pointed; the first quill
very small, second, third, and fourth longest. Tail rather long, emarginate, of
twelve rather strong feathers.