15 



is therefore greater. This may or may not be the case. The facts 

 observed will be sufficiently clear if it is remembered that the later in 

 the season a species moves the less hindrance it will meet from the ele- 

 ments, and the fewer pauses will be necessitated in its journey. Dur- 

 ing the mouth of May there are few if auy nights in which migration 

 does not take place; while a bird that migrates in March must expect 

 to be stopped by storms at least one week in four. 



In regard to the relative speed at which the different species travel, 

 all that can be said at present is that those which migrate later have, 

 as a rule, the highest rate. Thus the average speed of the Robin, Cow- 

 bird, and Golden- shafted Flicker is about 12 miles a day, while the aver- 

 age of the Summer Redbird, Baltimore Oriole, Ruby-throated Hummer, 

 and Nighthawk is 28 miles. If we try to calculate the relative speed of 

 the different families, we find that some of the species in a family mi- 

 grate early aud slowly, others late and rapidly, bringing the average 

 of most of the families very close to the general average of all, which, 

 as already stated, is 23 miles a day. 



Birds have seldom been seen while on their way in undisturbed mi- 

 gration at night. The observations given by W. E. D. Scott and J. A. 

 Allen (Bull. Nutt. Ornith. Club, Vol. VI, 1881, pp. 97-100, and 188) are 

 the most important, but in these nothing is said concerning the speed 

 at which the birds were supposed to be moving. It is known that birds 

 do not move rapidly, as a rule, when migrating in the day-time, but 

 from the meager material at hand it may be inferred that the speed at 

 night is considerably greater. During day-migration the smaller land 

 birds rarely fly faster than 15 miles an hour, though the larger birds, 

 such as Cranes, Geese, Ducks, etc., move much more rapidly. At Red 

 Rock, Ind. Ter., between August 25 and September 5, 1884, the Cliff 

 Swallows and Nighthawks were conspicuous every morning and even- 

 ing, slowly drifting south and southwest in their fall migration. For 

 an hour and a half parties of birds would pass by in almost unbroken 

 succession. Many hundred Nighthawks were seen during a single even- 

 ing, and the number of Swallows was much greater. The result of 

 timing them on several occasions gave a rate of about 10 to 14 miles an 

 hour, the former being the more usual speed. This slow rate was 

 caused by the irregularity of the flight, as the birds captured their 

 evening and morning meals on the wing. The morning flight lasted an 

 hour only, and was made at about the same speed. . Thus a distance of 

 about 30 miles would be traveled by each individual during the morn- 

 ing and evening together, but no one can say how much farther, if any, 

 they traveled during the night.* 



The advance of the hosts of Warblers, as they move incessantly for- 

 ward from tree-top to tree-top, is still slower, probably being but a few 

 miles during a whole day. Geese in their northward flight along the 



[*The material gathered from the keepers of light-houses seems to indicate that 

 neither Swallows nor Nighthawks migrate to any extent after night fall.— C. H. M.] 



