2 BIRD BEHAVIOUR 



and men, most of which differ from each other more 

 than the earliest known bird, the Archaofteryx of 

 Jurassic times, does from the modern Sparrow in the 

 back-garden. 



On the other hand, t^e numerous species and 

 families of birds and their close alliance with each 

 other afford, by this very narrow range of differentia- 

 tion, an attractive and philosophical study ; among 

 them survive types which in mammals have become 

 " missing links " or are only discoverable in the 

 fossil state. In fact, it is the survival of so many 

 connecting forms that makes it so difficult to group 

 the families of birds into larger " orders," a difficulty 

 which only occurs with mammals when we look 

 back among their fossil predecessors preserved among 

 the rocks. 



We look, for instance, with interest upon the 

 remains of the various ancestral predecessors of the 

 horse family, as exhibited in museums, and try to 

 realize what changes of habit must have occurred 

 to convert a small animal with paws into a large 

 one with a single hoofed toe on each foot. But 

 among the birds, if we go to the Duck family 

 {Anatidee) we find still in existence practically all 

 the links .between a light-bodied, large-winged bird 

 with non-waterproof plumage and half-webbed 

 feet with large grasping hind-toe, and almost 

 exclusively aquatic diving Ducks which rival the 

 Grebes and Cormorants in their subaqueous per- 

 formances, and exhibit almost as much modification 

 of structure. And the habits of these can be 



