132 BIRD BEHAVIOUR 



liarity I never observed in any other nestlings : they 

 kept their tails turned over on their backs, and 

 under their closed wings ; a most admirable ar- 

 rangement for the tight packing which is the lot 

 of nestlings reared in holes hacked out in trees, 

 as young Barbets are, but nevertheless young Wood- 

 peckers have not the habit, though similarly placed. 



The nestling most celebrated for its peculiarities 

 is that of the Hoatzin (Opisthocomus hoazin) of the 

 forests along the edge of some rivers in northern 

 South America. The adult bird is not unlike a 

 perching Pheasant in general form, size, and habits, 

 but the young are most curious creatures, clad at 

 first in a scanty down like that of a young Pigeon, 

 but nevertheless born open-eyed, not blind as Pigeons 

 .and other naked or nearly naked nestlings are ; they 

 are also able to clamber about the boughs, in which 

 action not only the bill and feet are brought into 

 play, but also the wings, which have claws at the 

 end of the first and second digits, the first digit in 

 birds being that little movable point which 

 supports the set of pigmy quills known as the 

 bastard- wing, which may be seen projecting at the 

 pinion- joint of a Pigeon's wing when it is about to 

 settle, and the second forming the tip of the 

 pinion. 



These claws of course represent two of the three 

 original claws found in the separate digits of the 

 primaeval birds' forelimb (which were probably 

 simply enclosed in a common skin like a Kingfisher's 

 toes), and so it is interesting to find them still in 



