140 



The Stork-like Birds 



is rather slow, although strong, and is accompanied by a continuous flapping of 

 the wings. In general they lay from three or four to six unspotted eggs, which 

 are bluish green or Whitish in color. 



The group is an old one, some half a dozen species having been found fossil, 

 the oldest being from the lower Eocene of England. A single fossil species (Ardea 

 paloccidentalis] has been found in North America, and another (A. megacephala) 

 has disappeared in comparatively recent times from the island of Rodriguez. 



Over one hundred living species are known, distributed, according to Sharpe, 

 among thirty-seven genera, but this number of genera is perhaps excessive, since 



FIG. 43. Great Blue Heron, Ardea herodias. 



the differences between some of the groups seem hardly worthy of full generic 

 rank. North America possesses some eighteen forms, these being lately referred 

 by American ornithologists to no less than eleven genera, most of which were 

 formerly accorded only subgeneric rank. 



The true Herons belong to the genus Ardea and number some dozen or more 

 species. They are quite variable in size, ranging from twenty-eight to fifty-six 

 inches in length; in color there is likewise considerable variation. Of the habits of 

 Herons in general, Hudson, in his "Argentine Ornithology," says: "Two inter- 

 esting traits of the Heron (and they have a necessary connection) are its tireless 

 watchfulness and its insatiable voracity; for these characters have not, I think, 

 been exaggerated even by the most sensational of ornithologists. In other birds 

 of other genera, repletion is invariably followed by a period of listless inactivity 

 during which no food is taken or required. But the Heron digests his food so 

 rapidly that, however much he devours, he is always ready to gorge again; conse- 



