When one recalls that most birds appear to be more or less helpless in the dark, it seems remarkable that many should select the night hours for extended travel. Among those that do, however, are the great hosts of shore birds, rails, flycatchers, orioles, most of the great family of sparrows, the warblers (fig. 4), vireos, and thrushes, and, in fact, the majority of small birds. That it is common to find woods and fields on one day almost barren of bird life and on the following day filled with sparrows, warblers, and thrushes, would indicate the arrival of migrants during the night. The passage of flocks of ducks and geese is frequently observed by sportsmen sitting in their blinds, but great numbers of these birds also pass through at night, the clarion call of the Canada goose (_Branta canadensis_) or the conversational gabbling of a flock of ducks being common night sounds in spring and fall in many parts of the country. The sibilant, nocturnal calls of the upland plover, or Bartramian sandpiper (_Bartramia longicauda_), and other shore birds during their spring and fall flights form vivid memories in the minds of many students of migration. Observations made with telescopes focused on the full moon have shown processions of birds. The estimate of one observer that birds passed his point of observation at the rate of 9,000 an hour gives some indication of the numbers of birds that are in the air during some of the nights when migration is at its height. While the passage of migratory birds has thus been recorded throughout the night, the bulk of the flocks pass during the earlier hours of the evening and toward daylight in the morning, the periods from 8 o'clock to midnight and from 4 to 6 a. m. seeming to be favorite times for nocturnal flight. It has been claimed, with some reason, that small birds migrate by night the better to avoid their enemies, and that most of the nocturnal travelers are those that are naturally timid, sedentary, or feeble-winged. Included in this group are not only small song and insectivorous birds, but also such weak fliers as the rails, as well as the wrens, the small woodland flycatchers, and other species, which, living habitually more or less in concealment, are probably much safer making their long flights under the protecting cloak of darkness. This cannot fully account for the nocturnal habit, however, since among the night migrants are the snipe, sandpipers, and plovers, birds that are generally found in the open and are among the more powerful fliers, some of them making flights of more than 2,000 miles across the ocean. Such exceptionally long flights, of course, require both day and night flying.