198 THE ANIMALS OF NEW ZEALAND 



enabling members of a herd to find their fellows at night, or to 

 follow the lead of others in escaping enemies. It usually occurs 

 in animals of gregarious habits, and we should judge therefrom 

 that Notornis is gregarious. It is all the more curious, then, 

 that isolated individuals should have been caught, and nothing 

 seen of their fellows. But from what enemy does the Notornis 

 flee ? What native animal of the present day preys on Notornis 1 

 Probably none. Then this 'recognition mark' must have come 

 down from a time and place in which there were enemies." 



Order Herodiones. 



Large birds with long legs, neck, and bill. Toes long and 

 slender, the hind toe not elevated above the others. Part of the 

 head and neck naked. 



Family Ardeidae. 



Bill long, strong, and acute. Wings rounded. Tail short. 

 Outer toe with a broad basal web ; middle claw pectinated. Space 

 between the mouth and the eves bare. 



Key to the Genera. 



1. Tail feathers ten. 2 

 Tail feathers twelve. 3 



2. Tarsus equal to luiddle toe. Ardetta. 

 Tarsus shorter than middle toe. Botaurus. 



3. Bare portion of tibia is less than inner toe and claw. Deuiiegretta. 

 Bare portion of tibia at least equal to inner toe and claw. 4 



4. Bill not longer than middle toe and claw. Herodias. 

 Bill longer than middle toe and claw. Notophoyx. 



Genus Herodias. 



Bill not serrated, but a distinct notch at the end of the upper 

 mandible ; not longer than the middle toe and claw. Tail feathers 

 twelve. No crest, but a well developed dorsal train. Nearly 

 cosmopolitan. 



