These arboreal forms live upon snakes, frogs, insects, and birds, the last of which they hunt in pairs, converging gradually on the victim from each side: the note is mournful; the small nest of twigs, lined with grass or leaves, is placed in trees; the two eggs are rufous or white with red markings. The slender _Polyboroïdes typicus_, of most of the Ethiopian Region, combines the appearance of a Harrier with that of a typical Hawk; it is grey with white tips to the black remiges and rectrices, and shews black and white bars on the lower breast and abdomen. A whitish band crosses the tail, while the naked cheeks and cere are yellow. _P. radiatus_ of Madagascar is more silvery. Resembling the following group in habits, these birds prefer grasslands, especially when newly burnt, take comparatively short flights, and rest more frequently on trees or stumps. They are said to be able to bend the tibio-tarsal joint either way. _Circus_, ranging over nearly the whole world, comprises some seventeen species, in most of which the sexes differ in coloration–an unusual fact in Raptorial forms. They are graceful and soft-plumaged, with long legs, wings, and tail, the partial facial ruff creating a likeness–superficial and not warranted by structure–to the owls. Non-arboreal and by nature shy, they may be seen hovering or circling aloft, or systematically beating over the flats with buoyant untiring flight, the pinions flapping slowly and regularly, and exposing a broad surface to the air. They can, however, move with rapidity, and approach their breeding-quarters {155}with a fine downward sweep, an exceptionally bold cock sometimes almost striking an intruder. The cry, chiefly heard during incubation, is shrill; the food consists mainly of small mammals, but partially of birds, reptiles, fish, frogs, insects, or even eggs; the nest, placed among reeds, corn or herbage, in gorse-coverts or on heathery or grassy slopes, is, according to circumstances, a pile or layer of the surrounding vegetation lined with the finer portions, and contains from three to six bluish-white eggs, rarely blotched with rufous. Nesting-sites in trees are on record. Three species still breed in Britain, _C. cyaneus_, the Hen Harrier, _C. cineraceus_, Montagu's Harrier, and _C. aeruginosus_, the Marsh Harrier or Moor Buzzard. The first two are much alike and easily confounded, the female in both being brown above and buffish with dark streaks below, while the tail is crossed by five umber bars. The male, which is bluish-grey with white rump and abdomen in the Hen Harrier, but is streaked beneath with rufous in the more slender Montagu's Harrier, is commonly considered a different species from the female by rustics, who call it the "Kite." These forms range over Europe, Asia, and North Africa; but whereas the first-named reaches about lat. 69° N. in summer, and occurs from Morocco and Abyssinia to Canton in winter, its congener is not found so far north, and migrates down to Cape