“Adult birds, either in winter plumage or perhaps in the second year, are blacker than in the summer plumage. Some of these black-plumage birds have ornamental feathers which looks as if they were fully adult, and therefore they may be birds of the second year, as it is quite evident that the grayer plumaged ones are very old and perfect in livery.
“The white streak down the throat is often absent or reduced to a few spots. It appears to be absent equally in quite young birds and in old ones also, and it may be the result of inherent melanism in the species.
“The white form is exactly similar in size to the gray form, and, when adult, has the same ornamental plumes. In the Pacific islands the two forms appear to interbreed, and produce white young ones mottled or streaked with slaty gray. I have been unable to recognize any of the many forms into which the reef heron has been subdivided by naturalists. Some birds are larger, as will be seen by the measurements of the tarsi given in detail below, and these larger birds have a slightly longer wing and a heavier bill, but no specific distinctions can be founded on these variations, which are very slight.” (Sharpe.)
“The color of the soft parts is excessively variable. In the adult the bare portion of the tibia varies from dark grass-green to greenish plumbeous; the back and sides of the tarsus and the greater part of the toes are generally pea-green, sometimes duller, sometimes yellower; the front of the tarsus and the first joint of the mid toe black, but sometimes these parts are green, only patched or mottled with black, and sometimes the black extends along the ridges of all the toes; the color of the bill and bare skin in front of the eye varies from sienna-brown to chocolate; sometimes the bill is a sort of light mahogany color, and the bare skin a sort of greenish brown; usually the bills are yellowish at the tips; the lower mandible is generally lighter, sometimes brownish horny, sometimes yellowish horny; and in the breeding-plumage the whole lower mandible becomes apparently a very decided, though dull, yellow; the irides vary from bright to deep yellow. I suspect, though we have not been able to work it out, that these differences in color are due both to age and to season.” (Hume.)
“Quite common along the reefs. The young were met with on various occasions far inland along fresh-water streams, but we never found fully mature birds in such localities.” (Bourns and Worcester MS.)
So far as observed, this species is solitary and found only on rocky shores, usually where coral flats are exposed at low tide.
Genus NYCTICORAX Forster, 1817.
Bill stout; legs rather short; tarsus about equal to middle toe with claw and little longer than exposed culmen; tarsus covered with hexagonal scales; head decorated with two or three long, slender, nuchal plumes and a full crest.