warbler have been collected in Mississippi, Florida, and the District 

 of Columbia as late as October. 



Students of migration know that birds generally travel in waves, 

 the magnitude of which varies with populations, species, weather, 

 and time of year. Characteristically, one will observe a few early 

 individuals come into an area followed by a much larger volume of 

 migrants. This peak will then gradually taper off to a few lingering 

 stragglers. If we plot numbers observed against time, the rising and 

 receding curve takes the form of a bell. In the northern part of the 

 United States there are two general migration waves. The first one in 

 early spring consists of "hardy" birds including many of our common 

 seed eaters like the finches, sparrows, and others. The second wave 

 occurs about a month later and consists primarily of insect-eating 

 birds, such as flycatchers, vireos, warblers, and the like. Each of 

 these species in turn has its own "curve" of migration in the major 

 wave. 



Time of Day 



Because most birds appear to be creatures of daylight, it seems 

 remarkable that many should select the night for extended travel. 

 Among the many nocturnal migrants are the smaller birds such as 

 rails, flycatchers, orioles, most of the sparrows, the warblers, vireos, 

 thrushes, and shorebirds. 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, which indicates the arrival of 

 migrants during the night. Waterfowl hunters sitting in their 

 "blinds" frequently observe the passage of flocks of ducks and geese, 

 but great numbers of these birds also pass through at night; the calls 

 of Canada geese or the conversational gabbling of a flock of ducks are 

 common night sounds in spring and fall in many parts of the country. 

 Observations made with telescopes focused on the full moon have 

 shown processions of birds, and one observer estimated their passage 

 over his area at the rate of 9,000 per hour. This gives some indication 

 of the numbers of birds in the air at night during peaks of migration. 

 At such times radar observations have shown that nocturnal 

 migration begins about an hour after sundown, reaches a peak 

 shortly before midnight, and then gradually tapers off until 

 daybreak. Unless special curcuits are installed in radar sets, bird 

 echoes during peak migration periods may cover a radar screen. 



It has been suggested that small birds migrate by night to avoid 

 their enemies. To a certain extent this may be true because the 

 group includes not only weak fliers, such as the rails, but also the 

 small song and insectivorous birds, such as wrens, small woodland 

 flycatchers, and other species that habitually live more or less in 

 concealment. These birds are probably much safer making their 

 flights under the protecting cloak of darkness. Nevertheless, it must 

 be remembered that night migrants include also the snipe, 

 sandpipers, and plovers. Most shorebirds are usually found in the 

 open and are among the more powerful fliers, as some of them make 



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