tremulous motion of the wing-feathers : others, again, contended 
that it was caused by the tail feathers. This was first mooted by 
the Danish naturalist, Meeves, and he produced some very 
striking and curious evidence to prove his view. He showed that 
the outermost tail-feathers had peculiarly thickened shafts, 
which were also bent in a very striking way. By removing these 
feathers, and sticking them into a cork, he was enabled, by 
twirling the cork rapidly round at the end of a string, to reproduce 
the “ bleat ” exactly. Many years later Dr. Philip Bahr revived 
this experiment, for the purpose of finally setting the matter at 
rest—for there were still many who remained unconverted to 
the Meeves interpretation. Dr. Bahr left no room for further 
doubt. He showed, too, that during the production of this 
sound these tail-feathers were extended laterally, so as to 
separate them from the rest of the tail, and so give the air rushing 
past them during the earthward plunge, full play on these sound- 
producing structures. He too, applied the test first instituted 
by Meeves, and so clinched his arguments. One may hear this 
strange music as early as February, and even, though rarely, 
as late as July. But it is essentially a breeding-season, or rather 
a “‘ Courtship ” performance sound, though it may be evoked by 
a sitting bird suddenly surprised, when she will ‘“ bleat” 
as she leaves her eggs, possibly to distract the intruder on 
her vigil. 
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