BRITISH BIRDS OF FASTEST FLIGHT 55 
to the body — an indication of rapid flight. The 
swift, a bird of passage which crossed the wade sea 
after breeding in Japan, is not known to alight 
in AustraHa, w^here it spends a considerable time 
hunting its insect prey in the upper air." 
In A History of the Birds of Europe,"^ 
Dresser writes : " The present species {Acanthyllis 
caudacuta or Chaetura caudacuta caudacuta) and 
Acanthyllis gigantea are said to be the swiftest 
birds in existence. Tickell says that he never 
witnessed anything equal to the prodigious swift- 
ness of its movements." 
Chaetura caudacuta cochinchinensis (which is 
to be found in Malacca, Sumatra, and Cochin 
China) is a form of the spine-tailed swift allied to 
that species {Chaetura caudacuta caudacuta) which 
is so rare a visitor here. I have examined and com- 
pared numerous specimens of these three species 
of spine-tailed swifts, and it would seem practic- 
ally certain, in view of their similarity in size and 
structure, that their speed must be similar. 
Mr. E. Stuart Baker, who has made experi- 
ments as to the speed of the Chaetura nudipes and 
the Chaetura cochinchinensis, writes : ^ " Both 
1 Vol. iv. p. 616. 
2 British Birds Magazine, vol. xvi. No. 1 (June 1, 1922), p. 31. 
