114 ESSAYS OF A BIOLOGIST 



joins its mate is also beautiful. Some little time be- 

 fore the human watcher notes the other's approach, 

 the waiting bird rises on its branch, arches and 

 spreads its wings, lifts its aigrettes into a fan and 

 its head-plumes into a crown, bristles up the feathers 

 of its neck, and emits again and again a hoarse cry. 

 The other approaches, settles in the branches near 

 by, puts itself into a similar position, and advances 

 towards its mate; and after a short excited space 

 they settle down close together. This type of greet- 

 ing is repeated every day until the young leave the 

 nest; for after the eggs are laid both sexes brood, 

 and there is a nest-relief four times in every twenty- 

 four hours. Each time the same attitudes, the same 

 cries, the same excitement; only now at the end of it 

 all, one steps off the nest, the other on. One might 

 suppose that this closed the performance. But no: 

 the bird that has been relieved is still apparently ani- 

 mated by stores of unexpended emotion; it searches 

 about for a twig, breaks it off or picks it up, and re- 

 turns with it in beak to present to the other. Dur- 

 ing the presentation the greeting ceremony is again 

 gone through; after each relief the whole business of 

 presentation and greeting may be repeated two, or 

 four, or up even to ten or eleven times before the free 

 bird flies away. 



When there are numerous repetitions of the cere- 

 mony, it is extremely interesting to watch the pro- 

 gressive extinction of excitement. During the last 

 one or two presentations the twig-bringing bird may 



