In November, when the moult is advanced. The bill is black, dull blue at the base. The feet are nearly black, as are the claws. The occipital feathers are now two inches and a half in length, and some of the dorsal feathers extend as far as the tips of the wings; those of the lower part of the neck have also a length of about three inches. The general colour of the plumage is white; the upper part of the head, the hind neck, back, anterior edge of the wing, and outer primaries at the end, of a faint bluish-grey tint; some of the elongated feathers of the back darker. Length to end of tail 22 inches; to end of claws 29-1/2; bill 3; wing from flexure 11-1/4. A year old. Bill nearly as in the adult; feet bluish-black, the plumage is white, with the upper parts pale greyish-blue as in November, but the whole interspersed with numerous feathers of a deep greyish-blue, similar to that of the adult; the primaries and tail being still white. Length to end of tail 23-1/4; extent of wings 32-1/2; bill 3-1/8. Weight 9 oz. At the age of a year the bird propagates, so that individuals in the white, mottled, or blue plumage, may be seen breeding together. When only a few weeks old, the serrature of the claw of the middle toe is scarcely perceptible, exhibiting merely faint indications of points upon a very slight margin. This margin enlarges, and when the bird is completely fledged the serratures are perfectly formed. In this bird, as in most other Herons, the crura of the lower mandible are thin, flexible, and elastic, the angle filled by an elastic membrane covered by the skin. The tongue is 1 inch long, sagittate at the base, tapering to a point. The roof of the mouth has a median prominent ridge, and two lateral lines; the palate is convex; the posterior aperture of the nares 10 lines in length. The pharynx may be dilated to 1-1/2 inch; the œsophagus, which is 12 inches long, is when dilated 10 lines in diameter at its upper part, and gradually contracts to 7 lines; at the curvature of the neck it lies directly behind, having passed down on the left side, along with the trachea. Its walls are extremely thin, contrasting in this respect with the œsophagus of the Great Northern Diver and other swimming piscivorous birds. The proventriculus is 1 inch long, its glandules cylindrical, and extremely slender. The stomach seems as if it merely formed a basal sac to the œsophagus, its muscles being extremely thin, its tendons circular and half an inch in diameter; cuticular lining soft. The intestine is long and very narrow, 5 feet 10 inches in length, 2 lines in diameter at the upper part, 1-1/2 near the rectum, which is 2-3/4 inches long, with a diameter of 4-1/2 lines, and terminates in a nipple-like cœcum, projecting 3 lines beyond the entrance of the small intestine, but having no appearance of the two lateral appendages usually called cœca. In this respect, the Blue Heron agrees with others of the same family.