FIELD STUDY IN ORNITHOLOGY. 475 



whole course, and in that case they wouhl naturally strike either Ice- 

 land or the west coast of Norway, and in either case would reach the 

 east coast of Britain. But, if by storms, and the prevailing winds of 

 the jSTorth Atlantic coming- from the west, they had been driven out of 

 their usual course, they would strike the coast of Norway, and so find 

 their way hither in the company of their congeners. 



As to the elevation at which migratory flights are carried on, Herr 

 Gatke, as well as many American observers, holds that it is generally 

 far above our ken, at least in normal conditions of the atmosphere, and 

 that the opportunities of observation, apart from seasons and unusual 

 atmospheric disturbance, are confined chiefly to unsuccessful and abor- 

 tive attempts. It is maintained that the height of flight is some 1,500 

 to 15,000 feet, and if this be so, as there seems every reason to admit, 

 the aid of land bridges and river valleys becomes of very slight impor- 

 tance. A tri: ial instance will illustrate this. There are two species of 

 blue-throat, Ci/anreula suceica and C. huvocyanu ; the former with its 

 red-breast patch is abundant in Sweden in summer, but is never found 

 in Germany, except most accidentally, as the other is the common form 

 of central Europe. Yet l)otli are abundant in Egypt and Syria, where 

 they winter, a!id I have on several occasions obtained both species out 

 of the same flock. Hence we infer that the Swedish bird makes its jour- 

 ney from its winter quarters with scarcely ahalt, while the other proceeds 

 leisurely to its nearer summer (piarters. On the other hand, I have 

 more than once seen myriads of swallows, martins, sand-martins, and, 

 later in the season, swifts, passing up the Jordan Valley and along the 

 Bukoa of central Syria, at so slight an elevation that I was able to 

 distinguish at once that th^ flight consisted of swallows or house-mar- 

 tins. This was in perfectly calm, clear weather. One stream of swal- 

 lows, certainly not less than a quarter of a mile wide, occupied more 

 than half an liour in i)assing over one spot, and flights of house-martins, 

 and then of sand-martins, the in-xt day, were scarcely less numerous. 

 These flights nnist have been straight U]) from the Red Sea, and may 

 have been the general assemldy of all those which had wintered in 

 East Africa. I can not think that these flights were more than 1,000 

 feet high. On the other hand, when standing on the highest peak in 

 the island of Palma, 0,500 feet, with a dense mass of clouds beneath 

 us, leaving nothing of land or sea visible, save the distant Peak of 

 Tenerife, 1*5,000 feet, I have watched a flock of Cornish choughs soaring- 

 above us, till at length they were absolutely indistinguishable by us 

 excejit with field-glasses. 



As to the speed with which the migration flights are accomplished, 

 they require much further observation. Herr Gatke maintains that 

 godwits and plovers can fly at the rate of 210 miles an hour ( !), and 

 the late Dr. Jerdon stated that tlie spine tailed swift {Aca^tln/Uis camla- 

 cntus)j roosting in Ceylon, would reach the Himalayas (1,200 miles) 

 before sunset. Certainly in their ordinary flight the swift is the only 



