120 BIRD BEHAVIOUR 



been speaking above, being exemplified by the 

 " nestling " young of Canaries, Budgerigars, Doves, 

 and Pigeons, while our ordinary poultry, with their 

 active running or swimming chicks, exemplify the 

 former. 



When we study the bird class family by family, 

 we shall find that the cleavage between these two 

 types of nestlings is very definite and complete ; 

 that is to say, they never both occur in the same 

 family. All young Pigeons, so far as is known, are 

 as helpless as those of the common Pigeon, even 

 in the case of those Ground-Doves found in America 

 and Australia which so closely resemble Partridges 

 in general habits ; and all young of the Duck family, 

 from the grazing Geese to the fishing Mergansers, 

 are as well able to "paddle their own canoe" as 

 the familiar domestic duckling. 



The two types crop up independently, moreover, 

 in very distinct families ; no one would think of 

 classing Pigeons and Hawks together because they 

 both have helpless young and feed them, or putting 

 Fowls and Ducks in the same group because in both 

 cases the young are active and more or less inde- 

 pendent. It will be seen that the two types of 

 young have no relation to the general habits of the 

 parents, whether carnivorous or vegetarian, terres- 

 trial or aquatic ; the production of one or the 

 other type may be regarded as a minor habit, 

 generally connected with the style of nest or 

 nesting-site used. Thus, birds which have a well- 

 developed perching foot, such as Pigeons, Herons, 



