THE WHITEHEAD 75 
fourth, its relation to the other three, and its 
interest in the nest, was harder to establish, for 
when a single member of the quadruple alliance 
arrived alone, it commonly awaited the presence 
of a second and third shareholder, frequently of 
both, before proceeding to deliver the goods. 
Whilst waiting thus, the solitary bird occupied 
itself in cramming its already well-filled maw, 
jerking the latest layers into place with beak 
pointed upwards, so as not to drop the lower 
stratum of booty—much as a boy, face to sky, 
attempts to get a cherry into his mouth by the 
stem. Sometimes, however, as many species do, 
rather than waste time, the billful was swallowed, 
and the bird flew off to seek fresh provender. 
Again and again it was possible to swear to three 
Separate birds, each definitely distinguishable by 
the insect wings, legs, and bodies in its beak ; 
the fourth was the difficulty. It was a bird which 
appeared to be partly engaged in feeding the 
brood, and partly engaged in acting as outlook 
or scout. The plumage of the sexes being but 
slightly differentiated, it was impossible to tell if 
one and the same bird always acted guard, if in 
fact the responsibility of scouting was shared or 
was settled by arrangement or by chance. It 
was not until the youngsters were taken from the 
nest and placed on a twig preparatory to being 
photographed, that all four parents showed them- 
