HOATZINS. 



247 



of the Rallidce. Many of its anatomical characters, its osteology, and the 

 peculiarities of the young birds, show that the genus Opisthocomus is an 

 isolated form, probably the survival of some ancient stock of birds, of which 

 it is the only survivor. Fossilized remains of a bird like the hoatzin have 

 been found in France, so that the type may have been far more widely 

 spread in ancient times, and have been distributed over certain portions of 

 the Old World. 



One curious feature about the hoatzin is the size of its crop, which is situ- 

 ated in a deep cavity in the upper half of the pectoral muscles. It occupies 

 the upper part of the chest, and is so enormous 

 as to distort the f urcula and sternum. The nest- 

 ling is hatched naked, and has a well-developed 

 claw on the pollex and index fingers of the wings, 

 so that it is able to crawl about by their means. 

 Mr. J. J. Quelch, the Director of the Museum at 

 Georgetown in British Guiana, has written a 

 most interesting account of the hoatzin, from 

 which w r e have extracted the following notes : 

 ' ' Soon after the hatching of the eggs, the nest- 

 lings begin to crawl about by means of their 

 wings and legs, the well-developed claws on the 

 pollex and index being constantly in use for hold- 

 ing and hooking on to the surrounding objects. 

 If the birds are drawn from their nest by means 

 of their legs, they hold on firmly to the twigs 

 both with bill and wings ; and if the nest be 

 upset by means of a rod pushed up from below, 

 they hold on to all objects with which they come 

 in contact by means of bill, feet, and wings, mak- 

 ing considerable use of the bill, not only to reach objects above them, but 

 also with the help of the clawed wings to raise themselves to a higher level. 

 One curious feature noticed with a nestling which had been upset in the 

 river, was its power of rapid swimming and diving when pursued. As soon 

 as the hand was placed close to it, it rapidly dived into the dark water, in 

 which it was impossible to see it, and would rise at distances of more than a 

 yard away. Owing to this power, the little creature managed to evade all my 

 attempts to seize it, taking refuge eventually under the bushy growth, where 

 it was impossible to pursue it. The prolonged immersion which a nestling 

 will thus instinctively and voluntarily undergo, or which an adult bird will 

 bear in an attempt to drown it, seems to me to be quite remarkable. 



"The nestlings, when resting on the bare sticks of the nest, are observed 

 to rest the weight of the body, as in the adult birds, on the bare and 

 thickened integument of the carina sterni, the toes being spread out and the 

 wings generally drawn up to the side." 



The food of the adult hoatzin consists of leaves or fruit, and the birds 

 after death have a very unpleasant odour, which prevents them being eaten 

 as food. They are incapable of sustained flight, and in this fact we see 

 another rail-like characteristic. Mr. Quelch observes : " Whether from the 

 fact of their occupying situations where they are but seldom disturbed, or 

 but little likely to be pursued, or from a natural weakness of wing, the birds 

 are but seldom seen in flight ; and when they take to the wing during dis- 

 turbance, they do so for but a very short distance a very exceptional flight 



Fig. 15. THE HOATZIN 

 (Opisthocomus cristatus). 



