Besides the humming-birds I have mentioned, there were four or five other small ones that we used to call squeakers, as it is their habit for a great part of the day to sit motionless on branches and every now and then to chirp out one or two shrill notes. At first I thought these sounds proceeded from insects, as they resemble those of crickets; but they are not so continuous. After a while I got to know them, and could distinguish the notes of the different species. It was not until then that I found out how full the woods are of humming-birds, for they are most difficult to see when perched amongst the branches, and when flying they frequent the tops of trees in flower, where they are indistinguishable. I have sometimes heard the different chirps of more than a dozen individuals, although unable to get a glimpse of one of them, as they are mere brown specks on the branches, their metallic colours not showing from below, and the sound of their chirpings--or rather squeakings--being most deceptive as to their direction and distance from the hearer. My conclusion, after I got to know their voices in the woods, was that the humming-birds around Santo Domingo equalled in number all the rest of the birds together, if they did not greatly exceed them. Yet one may sometimes ride for hours without seeing one. They build their nests on low shrubs--often on branches overhanging paths, or on the underside of the large leaves of the shrubby palm-trees. They are all bold birds, suffering you to approach nearer than any other kinds, and often flying up and hovering within two or three yards from you. This fearlessness is probably owing to the great security from foes that their swiftness of flight ensures to them. I have noticed amongst butterflies that the swiftest and strongest flyers, such as the Hesperidae, also allow you to approach near to them, feeling confident that they can dart away from any threatened danger--a misplaced confidence, however, so far as the net of the collector is concerned.