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. 



Night travel is probably best for the majority of birds chiefly from 

 the standpoint of feeding. Digestion is very rapid in birds and yet the 

 stomach of one killed during the day almost always contains food. 

 To replace the energy required for long flight, it is essential that food 

 be obtained at comparatively short intervals, the longest of which 

 in most species is during the hours of darkness. If the smaller mi- 

 grants were to make protracted flights by day they would be likely to 

 arrive at their destination at nightfall almost exhausted, but since they 

 are entirely daylight feeders, they would be unable to obtain food until 

 the following morning. This would delay further flights and result 

 in great exhaustion or possibly even death were they so unfortunate 

 as to have their evening arrival coincident with unusually cold or stormy 

 weather. Traveling at night, they pause at daybreak and devote the 

 entire period of daylight to alternate feeding and resting. This permits 

 complete recuperation and resumption of the journey at nightfall. 



Many species of wading and swimming birds migrate either by day 

 or night, as they are able to feed at all hours, and are not accustomed 

 to seek safety in concealment. Some diving birds, including ducks 

 that submerge when in danger, sometimes travel over water by day 

 and over land at night. The day migrants include, in addition to some 

 of the ducks and geese, the loons, cranes, gulls, pelicans, hawks, swal- 

 lows, nighthawks, and the swifts. All of these are strong-winged 

 birds. The swifts, swallows, and nighthawks (sometimes called bull- 

 bats) feed entirely on flying insects, and use their short, weak feet and 

 legs only for grasping a perch during periods of rest or sleep. Thus 

 they feed as they travel, the circling flocks being frequently seen in late 

 summer working gradually southward. Years ago before birds of 

 prey were so thoughtlessly slaughtered, great flocks of red-tailed. Swain- 

 son's, and rough-legged hawks might be seen wheeling majestically 

 across the sky in the Plains States, and in the East the flights of broad- 

 winged. Cooper's, and sharp>-skinned hawks are still occasionally seen. 

 To the birds of prey and possibly to the gulls also, a day's fasting now 

 and then is no hardship, particularly since they frequently gorge 

 themselves to repletion when opportunity is afforded. 



An interesting comparison of the flights of day and night migrants 

 may be made through a consideration of the spring migrations of the 

 blackpolled warbler and the cliff swallow. Both spend the winter in 



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