ECOLOGICAL 71 



admitted that migratory movements are spread over the greater 

 part of the year. And again, although the tide flows on the whole 

 north in spring, and ebbs to the south in autumn, there are many 

 diagonal movements; and the autumnal flight of many European 

 birds is from east to west, to begin with at least. Moreover, though 

 there are favourite migration-routes, such as along coast-lines, 

 chains of islands, and river- valleys, it must be recognised that the 

 advance and retreat are often general over broad belts of country. 

 One other caution at this stage may be permitted, that while we are 

 sure, from marked birds, that the migration flight may cover several 

 thousand miles, as in the case of the European swallows and storks 

 that have been found wintering in South Africa, the range may 

 extend for only a short distance. Yet the phenomena are the same 

 whether inconspicuous or grandiose. One of the grandest is that of 

 the Pacific golden-plover, which returns across the pathless sea from 

 the breeding-places in Alaska to the winter quarters in Hawaii. 



The facts of bird-migration are interesting, and it is a pity that 

 they have been at times exaggerated. This has certainly been the 

 case in regard to the velocity of flight, the estimates of which have 

 sometimes reached 250 miles an hour! It may be safely said that 

 migration velocities of over 50 miles an hour are rare; and there 

 is no warrant for supposing that migrating birds sustain that 

 accelerated flight which they show for a short time when in pursuit 

 of prey. Migrating crows seem to fly at a rate of about 30 to 45, 

 falcons at 40 to 48, geese at 42 to 55, ducks at 44 to 59 miles per 

 hour. As to the length of uninterrupted flight, there is no possi- 

 bility of resting (except on the sea) on or near the direct route from 

 Alaska to Hawaii, some 2,000 miles; but so long a flight without a 

 break is probably an altogether exceptional, though not unique, 

 feat. Even strong birds like storks take many rests on the lands 

 over which they travel in their autumnal flight from North Europe 

 to South Africa. It is probable that 200 miles is good work for a 

 migrating :tork, and that its day does not exceed eight hours. 

 The record for actual length of migrational range is to the credit 

 of the Arctic tern, which may spend our winter in the summer of 

 the Antarctic Circle ! 



According to the famous Heligoland observer, Gatke, migrating 

 birds usually travel at great altitudes, perhaps 20,000 feet, though 

 he admitted that there is also much migration at low levels, as in 

 the case of hooded crows, starlings, and skylarks. But Gatke's 

 estimates were based on theoretical and fallacious assumptions, and 

 the actual observations made by airmen show that few birds are 

 encountered at levels above 3,000 feet. Lucanus concludes that 

 most flight takes place below 1,300 feet, and that flight above 

 3,300 feet is exceptional. Meinertzhagen concludes that the few 

 birds met with above 5,000 feet are the exception, and that the 



