The quail also has

the oesophagus widened out at the lower extremity, and in the
aegocephalus and the owl the organ is slightly broader at the bottom
than at the top. The duck, the goose, the gull, the catarrhactes,
and the great bustard have the oesophagus wide and roomy from one
end to the other, and the same applies to a great many other birds. In
some birds there is a portion of the stomach that resembles a crop, as
in the kestrel. In the case of small birds like the swallow and the
sparrow neither the oesophagus nor the crop is wide, but the stomach
is long. Some few have neither a crop nor a dilated oesophagus, but
the latter is exceedingly long, as in long necked birds, such as the
porphyrio, and, by the way, in the case of all these birds the
excrement is unusually moist. The quail is exceptional in regard to
these organs, as compared with other birds;