TERNS. 399 



been already named : and there is also a traceable relation 

 between the heights at which they breed and the distances 

 to which they range over the ocean. 



SABINE'S GULL (Larus Sabini). 



Has been seen as a very rare winter straggler on the coast 

 of Ireland ; but as it has been seen only once, and does not 

 in any essential particular differ from the others, a detailed 

 account of it is not necessary. 



TERNS (Sterna). 



The terns have much more the form and character of air 

 birds, than even the lightest made and best winged of the 

 gulls. They are so continually on the wing, and so rapid 

 and varied in the use of it, that they have been called " sea 

 swallows." They have their wings pointed, and most of 

 them their tails forked like the swallows ; and though they 

 do not catch their food open-mouthed in the air as the 

 swallows do, or have their bills adapted for such a purpose, 

 yet they are very swallow-like in their motions. Over the 

 surface of the sea there are few winged insects to capture, 

 as there is neither food nor resting-place for them there ; 

 but the number of minute creatures contained in the water 

 is very great, and these are always coming to the surface, 

 especially when the water is a little agitated. When the 

 waves roll considerably, they are worked towards the lines 

 of least agitation on the slope, and the terns hawk about 

 and capture them, and alight on these lines even when there 

 is a considerable swell Their prey is smaller than that of 

 the gulls, and they seldom need to swim, and never dive, 

 in quest of it : but though they do not swim habitually, they 

 are so constructed as that they can recover themselves and 

 escape, if they happen to be caught in the water, or even in 

 the breakers. The fry of fish, when in the younger state, 



