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1921.] Velocity of Migratory Flight among Birds. 
that birds only fly at their fastest when pursuing or when 
pursued. Anyone who has watched a Falcon being flown 
at a hook will be struck by the speed which the usually 
leisurely-flapping hook can attain from the moment he 
realizes he is the quarry. 
I have seen hooks travelling on migration, and accurate 
observation gives their pace as from 38 to 40 miles 
per hour. Now these migratory Hooks were travelling 
in their usual leisurely fashion, and not at anything like 
the speed they can use when attacked bv a Falcon. All 
other migrations which I have witnessed in many and various 
parts of the world confirm my belief that migratory flight 
differs in no way from every-day movement, except that it 
is steadier and possibly a trifle slower. 
So in dealing with this question, 1 shall consider estimates 
of any normal flight as the normal velocity which birds 
attain on migration. That birds can hurry I do not doubt, 
but such effort could not belong sustained, and would be of 
little use to them in the long-distance migratory journeys 
they are accustomed to take. 
I shall first deal with those estimates of velocity which 
previous writers have recorded, but which cannot be regarded 
as reliable. Giitke claims that Hooded Crows fly at 
108 miles per hour and Bluethroats at 180 whilst on 
passage, and especially in the spring. 4 He claims that 
Bluethroats pass from between 10 and 27 degrees of 
northern latitude to the 54th degree of northern latitude 
in nine hours. He also assumes that the American Golden 
Plover takes but fifteen hours from Labrador to northern 
Brazil, supporting this theory by his personal observations 
on Godwit and Curlew covering over 7000 yards in sixty 
seconds, or at the rate of over 4 miles a minute ! 
His estimate of Hooded Crow flight is based on the 
assumption that their line of flight is from east to west 
over Heligoland, and that they make for the east coast of 
England. This apparently is not the case, for their line 
of autumnal flight over Heligoland is from north-east to 
south-west, and these are probably not the birds which 
