The most numerous of the residenters are the scarfs. In summer and winter they are always on the island, and apparently there is an abundant supply of suitable food in the vicinity, for they never go far away. During winter they congregate on the rocks in large flocks or colonies, and they have become so accustomed to man’s presence that they fly only when one approaches within a few yards of them. In very stormy weather they seek refuge in some sheltered spot, far enough away from the coast-line to be safe from the encroaching waves, and only when frightened by any one approaching too near do they choose what is, in their opinion, the lesser of two evils, and seek safety in flight. With the advent of spring they, like all other birds, turn their thoughts to love. Their comparatively homely winter dress gradually changes to one more appropriate to this sentiment and more in harmony with the imposing surroundings. Early in the year their plumage assumes a greener tint, and the graceful tuft or crest on the top of the head becomes more and more prominent. This crest practically disappears about the end of June, and seems to be a decoration in both sexes only during the nuptial season. Usually they manage to get through with their love-making and selecting of partners by the middle of March, after which the operations of nest-building are undertaken. In Orkney we associate a scarf’s nest with some almost inaccessible cliff, but such is not the case on Sule Skerry, for the simple reason that there are no cliffs. The nests are built all over the island, but principally near the coast-line; and the sociableness of the bird’s disposition shows itself in this fact, that they tend to crowd their nests together in certain selected spots, to which they return year after year. One place in particular, a patch of rough, rocky ground from forty to fifty yards square, I have named the scarf colony on account of its numerous population during the breeding season. Here in 1898 I counted fifty-six nests. As to the materials used for nest-building, these are principally seaweed and grass, but the scarf is not very particular as to details, and uses anything that will suit the purpose. I have found pieces of ordinary rope, even wire rope, and small pieces of wood used, and a very common foundation is the skeleton of a rabbit which has died during the winter. During building operations I have observed that one bird builds and the other brings the materials. After all has been completed, three, four, and sometimes five eggs are laid. Three is the most common number; five is rare. During incubation the one bird relieves the other periodically. It is a common sight to see one come in from the sea, sit down at the edge of the nest, and hold a long palaver with its mate. The sitting bird then gets up and flies out to sea, the other taking its place.