TEFNS. 509 



Gregarious and noisy in their habits, the gulls and terns are chiefly frequenters 

 of the coasts, although many of them may be found on inland waters, while 

 all may be driven inland by stress of weather. Even in England gulls may be 

 seen following the plough in search of worms ; and in parts of Argentina, as in 

 the Colina district, at a distance of some two Hundred miles from the sea, they 

 appear to dwell permanently inland, nesting in the lagunas. In Britain, while some 

 species breed on coast-clifFs, others nest on islands and inland lakes, grassy downs, 

 and peat-mosses. All the members of the group are birds of powerful and sustained 

 flight, and are capable of floating in the air with scarce a movement of their wings, 

 while they are equally at home on the surface of the water, where their webbed 

 feet enable them to swim with facility. The terns are, however, more essentially 

 aerial and aquatic birds than the gulls, their short legs not being well adapted for 

 walking on land. In the neighbourhood of the sea the food of all these birds con- 

 sists mainly of fish and refuse, but when inland they consume worms, insects, the 

 eggs and young of other birds, and the offal from slaughter-houses. Although the 

 group as a whole has a cosmopolitan distribution, it is noteworthy that in the great 

 area lying between South America and the neighbourhood of Australia and New 

 Zealand not a single gull is to be met with, although terns are abundant. Along 

 the southern shores of Australia, and also in New Zealand, a large, dark-mantled 

 gull (Larus pacijicus) makes its appearance as an isolated form. Geologically, the 

 group appears to be one of the oldest of the existing orders of birds, remains of an 

 extinct genus (Halcyornis) occurring in the London Clay, a formation belonging to 

 the lowest division of the Tertiary period ; while other forms, which have been 

 assigned to the existing genus Larus, occur in beds pertaining to the lower portion 

 of the Miocene period. According to the classification adopted by Mr. Howard 

 Saunders, the order may be divided into two families, the first of which is again 

 split up into three subfamilies. 



The Terns, Skimmers, and Gulls. 



Family Laeid^^. 



Including the three groups above-named, each of which represents a subfamily, 

 the present family is characterised as follows. The beak has no cere at its base ; 

 there are two notches on each side of the hinder margin of the breast-bone ; the 

 toes may be either partially or fully webbed ; and the claws are feeble or of 

 moderate length. 



The terns, of which eleven genera are recognised by Mr. Saunders, 

 constitute a subfamily (Sternince), characterised by the straight and 

 rather slender beak, in which the two mandibles are of nearly equal length ; by the 

 feather-tracts resembling those of the plovers in their arrangement ; and by the 

 slight or distinct forking of the tail. In Britain the group is represented by two 

 genera, and it is to these that our notice is mainly confined. The marsh terns form 

 a genus (Hydrochelidon) represented by four species, three of which are British. 

 Belonging to a group of genera, in which the tail may be either nearly square or 

 deeply forked, and the head devoid of elongated plumes at the gape of the mouth, 



