74. EVERYDAY BIRDS 
But the looker-on is likely to be quite as much 
impressed by what he sees as by what he hears. 
During the whole performance, but especially 
during the latter part of it, the bird is engaged 
in the most violent contortions, suggestive of 
nothing but a patient suffering from uncontrol- 
lable nausea. Moreover, as soon as the prelimi- 
nary hiccoughs begin, the lower throat or breast 
is seen to be swelling; the dilatation grows 
larger and larger till the pumping is well under 
way, and so far as my companion and I could 
detect, does not subside in the least until the 
noises have ceased altogether. 
How are the unique, outlandish notes pro- 
duced? I cannot profess to know. Our opinion 
was that the bird swallowed air into his gullet, 
gulping it down with each snap of the beak. To 
all appearance it was necessary for him to inflate 
the crop in this way before he could pump, or 
boom. As to how much of the grand booming 
was connected with the swallowing of the air, 
and how much, if any, with the expulsion of it, 
my friend and I did not agree, and of course 
neither of us could do more than guess. 
I made some experiments afterwards, by way 
of imitating the noises; and these experiments, 
together with the fact that the grand booming 
seemed to be really nothing more than a develop- 
