With regard to the nidification of the White-bellied Sea-eagle, I could not fail to remark how readily the birds accommodate themselves to the different circumstances in which they are placed; for while on the main land they invariably construct their large flat nest on a fork of the most lofty trees, on the islands, where not a tree is to be found, it is placed on the flat surface of a large stone, the materials of which it is formed being twigs and branches of the Barilla, a low shrub which is there plentiful. While traversing the woods in Recherche Bay, I observed a nest of this species near the top of a noble stringy bark tree (_Eucalyptus_), the bole of which measured forty-one feet round, and was certainly upwards of 200 feet high; this had probably been the site of a nest for many years, being secure even from the attacks of the natives, expert as they are at climbing. On a small island, of about forty acres in extent, opposite the settlement of Flinders, I shot a fully-fledged young bird, which was perched upon the cone of a rock; and I then, for the first time, discovered my error in characterizing, in the “Proceedings of the Zoological Society of London,” and in my “Synopsis,” the bird in this state as a different species, under the name of _Haliæetus sphenurus_, an error which I take this opportunity to correct. The eggs are almost invariably two in number, of a dull white, faintly stained with reddish brown, two inches and nine lines long, by two inches and three lines broad. This Sea-eagle may be frequently seen floating about in the air above its hunting ground, in circles, with the tips of its motionless wings turned upwards; the great breadth and roundness of the pinions, and the shortness of the neck and tail, giving it no inapt resemblance to a large butterfly. The sexes are alike in plumage, but the female is considerably larger than her mate. Adults have the head, neck, all the under surface, and the terminal third of the tail-feathers white; primaries and base of the tail blackish brown, the remainder of the plumage grey; irides dark brown; bill bluish horn-colour, with the tip black; cere, lores, and horny space over the eye bluish lead-colour slightly tinged with green; legs and feet yellowish white; nails black. The young have the head, back of the neck and throat light buff; all the upper surface and wings light chocolate-brown, each feather tipped with buffy white; tail light buffy white at the base, passing into deep brown towards the tip, which is white; chest brown, each feather margined with buff; abdomen mingled buff and brown, the latter colour occupying the margins of the feathers; under tail-coverts, and the under surface of the tail-feathers white; bill brown; feet yellowish white. The Plate represents an old and a young bird, the former about half the natural size. [Illustration: HALIASTUR LEUCOSTERNUS. _J. Gould and H. C. Richter del et lith._ _C. Hullmandel Imp._ ]