346 TROPICAL WILD LIFE IN BRITISH GUIANA 



The proportions of the wing upon hatching are much 

 the same as those of the adult, except that the arm is a little 

 longer and the forearm a little shorter, while the hand re- 

 mains about the same. The main variation during growth 

 takes place between the forearm and the arm, the former 

 increasing proportionally as the latter decreases. The hand 

 parallels the forearm and increases slowly but steadily until 

 the young heron is fully fledged. It greatly exceeds the 

 adult in length at this time, but for the rest of the developing 

 period which lasts for several weeks it decreases until the 

 bird is mature. In this respect it closely resembles the hand 

 of the hoatzin, though its excess of length is not so great, 

 and there are no large claws to reduce. 



Notwithstanding the fact that the young herons, like 

 the young hoatzins, climb about the tree or bush where their 

 nest is situated, before being able to fly, they have no wing 

 claws. They are a curious combination of precocious birds 

 and those that are born helpless. For the first ten days 

 or two weeks after hatching they are as helpless in their nest 

 as any nidicolous bird, but after that long before they de- 

 velop flight they may be seen moving freely about among 

 the maze of branches near their nest. They seldom use their 

 wings to climb with, but rely chiefly upon their great wide- 

 spread toes to carry them to safety from a chance pursuer. 

 The erect position and great feet enable them to do by bal- 

 ance what the hoatzin has to do by crawling and clinging. 

 If by rare chance, they do lose their equilibrium, the instinct 

 of many forgotten ages comes to their aid and out go the 

 wings to brace against the nearest hold as naturally as they 

 did many thousands of generations ago. It is undoubtedly 

 largely due to the acquired erect posture of body and there- 

 fore ease of balance, that the wings have lost their claws, for 

 as the habit of balance increased, so must the use for func- 

 tional fingers have decreased, until as useful members they 

 became obliterated. 



In one of the toucans at least, and in some of the Pas- 



