The Mergansers are a well-defined little group of fish-eating Ducks, forming the sub-family Merginæ. They are characterised by their slender, narrow bill, furnished on both upper and lower mandible with saw-like lamellæ or denticulations. The head is always more or less crested; in most other respects they resemble the Diving Ducks, all the species seeking for their food by diving. The sexes differ in colour of plumage, but not, perhaps, to such a marked extent as in some other divisions of the Anatidæ. Six species of Mergansers are known to science, of which four are included in the British list—one as a rare visitor from North America. Of the remaining two species, one inhabits South America, the other the Auckland Islands. The young, as usual, are hatched covered with down, and able soon to follow the female to the water. In their moulting and progress to maturity they resemble preceding species. RED-BREASTED MERGANSER. This handsome sea-bird, the _Mergus serrator_ of Linnæus and most modern ornithologists, is unfortunately a winter visitor only to English waters. In Scotland and Ireland, however, it is one of the most familiar coast birds all the year round. The Red-breasted Merganser cannot readily be confused with any other Duck. The crested head and upper neck are black, shot with green and purple, the lower neck and upper breast are buff, streaked with black, the feathers on the sides of the breast having broad black margins, the flanks are strongly vermiculated with black, the back is black, vermiculated with gray on the lower portions, the inner scapulars are black, the outer ones white, the speculum is white, barred with black, and the underparts (except the flanks) are white. The female has the head and neck reddish-brown, and the upper parts brown, the black-bordered feathers on the sides of the breast are absent. Although found in many inland districts, the favourite resorts of the Red-breasted Merganser are wild, rocky coasts, such as contain plenty of quiet bays and creeks, and lochs studded with islands. Waters where the bottom is sandy or rocky, are preferred to those in which it is composed of mud. Many birds of this species visit our coasts for the winter from more northern haunts, whilst some of those dwelling in Scottish waters draw southwards at that season. This Merganser is more or less gregarious, and may be met with in flocks out at sea, or during rough weather sheltering nearer the land in lochs. Early in spring, and onwards through the summer, the Red-breasted Merganser lives closely in pairs, flying and feeding in company. I have noticed that this bird visits certain spots to feed very regularly, according to the state of the tide; almost to the minute I could depend upon certain pairs passing certain spots on their way to these feeding-grounds. I know of few prettier sights than the actions of a pair of Mergansers in some quiet, deep sea loch in early summer.