1 91 9-] ^^" ^^'^ Height at ivhich Birds mifirafe. 321 



Polatzek also remarks that he noted some " as late as 

 June." Apparently this must have been in another year. 



Range. The Rock-Martin breeds in the Atlas Movmtains 

 and in the Mediterranean countries, and winters in north- 

 east Africa. The extent of its winter range on the west 

 coast of Africa seems to be little known. 



[To be continued.] 



XVII. — Notes on the Height at ivhich Birds migrate. 

 By Capt. CoLLiNGWooD Ingram^ M.B.O.U. 



The height at which birds migrate is one of the branches 

 of ornithology upon wiiich we are still profoundly ignorant. 

 With the exception of one or two chance observations made 

 througli astronomical telescopes, until the advent of aero- 

 planes, our knowledge of the subject was limited to the 

 range of human vision above the earth's surface. 



W. E. D. Scott, of Princeton, U.S.A. [cf. ' Story of a 

 Bird Lover,' New York, 1903), and F. M. Chapman 

 [cf. Auk, 1888) were the first to publisli authentic records 

 of birds travelling at considerable elevations. 



These naturalists detected birds tlying across- the moon^s 

 face while making telescopic observations of that luminary. 

 Mr. Chapman^s remarks are interesting : " During the first 

 half- hour of observation (which lasted from 8 p.m. to 

 10.50 P.M., Sept. 3, 1887) a )iumber of birds were seen 

 flying upwards . . . these evidently being birds which had 

 arisen in our immediate neighbourhood and were seeking 

 the proper elevation at which to continue their flight ; but 

 after that time the line of flight was parallel to the earth's 

 surface, the general direction being south." He was able 

 to recognize Carolina Rails, Grackle, Snipe, and Duck. 

 These he estimated crossed in front of the lens at elevations 

 varying from 6000 ft. to 14,000 ft. 



The height at which birds migrate is undoubtedly governed 

 very laigely by the meteorological conditions prevailing at 

 the time, and when the air is inclined to be thicker heavily 

 charged with moisture (if birds arc migrating at all in such 



