THE TERN8 OB SEA-SWALLOWS. 331 



neath its wing, as at all seasons and in every sea they had 

 been remarked flying, while there appearance on land was 

 never noticed: 



"The bird of Thrace, 

 Whose pinion knows no resting-place." 



It is true that the petrels do not quit the sea except at the 

 time of laying, and for the purpose of making their nests 

 upon very precipitous rocks, where they feed their young 

 on half-digested animals. They retire there during the 

 night, and utter a most disagreeable cry, resembling the 

 croaking of a reptile. 



The Terns or " Sea-swallows " have remarkably long 

 wings and slender bills; the tail is forked, and the plum- 

 age generally is of a delicate pearl-white, with more or 

 less black upon the head. The terns are continually on the 

 wing, and although web-footed, are not seen to SAvim ; they 

 rest but seldom, and only on the land, feeding for the most 

 part on small fish and mollusca, which they seize upon the 

 surface of the water, but they also catch aerial insects. In 

 flying they send forth sharp and piercing cries. The most 

 elegantly formed of the terns is that called the " Roseate," 

 the mantle of which is a pale tint, the under-parts of a 

 rosy hue. Mr. Selby tells us that on the Fame Islands it 

 breeds abundantly. "When intruding on the nest, the 

 bird showed great anxiety, approaching so near that Ave 

 knocked one or two down with a fishing-rod used by the 

 keeper of the lighthouse for fishing from the rocks. All the 

 terns are very light, the body being comparatively small, 

 and the expanse of wings and tail so buoys them up that 

 when shot in the air they are sustained, their wings fold 

 above them, and they whirl gently doAvn like a shuttlecock." 

 The species are numerous and occur in both hemispheres. 



The Skimmers, although possessing much of the general 

 habits of the terns, are distinguished by the singular form 

 of the bill, the upper mandible of which is considerably 



