[Illustration: _Figure 4. Migration of the cliff swallow. A day migrant that, instead of flying across the Caribbean Sea as does the blackpoll warbler (see Fig. 3), follows the coast of Central America, where food is readily obtained._]
Although most of our smaller birds make their longest flights at night, close observation shows travel is continued to some extent by day. During the latter half of a migratory season birds may show evidence of an overpowering desire to hasten to their breeding grounds. At this time flocks of birds maintain a movement in the general direction of the seasonal journey while feeding on or near the ground. Sometimes they travel hurriedly, and while their flights may be short, they can cover an appreciable distance in the course of a day.
There is a widespread misconception among people concerning the speed at which birds can fly. One often hears stories of birds flying "a mile a minute." While undoubtedly some birds can and do attain this speed, such cases are exceptional, and it is safe to say that, even when pressed, few can develop an air speed of 60 miles per hour. Birds generally have two greatly differing speeds, one being the normal rate for ordinary purposes, and an accelerated speed for escape or pursuit. All birds, except the heavy-bodied, small-winged species such as auks, grebes, and other divers, have a reserve speed that may be double the normal rate.
Although it was thought for a long time that migratory flights were made at normal cruising speeds, Harrisson (1931) and Meinertzhagen (1955) showed that migration speeds were in between cruising speeds and escape speeds. The theory that migrating birds attain high speeds received encouragement from the German ornithologist Gatke (1895) who, for many years, observed birds at the island of Heligoland. He postulated that the bluethroat, a species of thrush smaller than the American hermit thrush, could leave African winter quarters at dusk and reach Heligoland at dawn; this flight would mean a sustained speed of 200 miles per hour! He also thought the American golden plover flew from the coast of Labrador to Brazil in 15 hours at the tremendous speed of 250 miles per hour. Most ornithologists now consider these conclusions to be unwarranted.