FLAT-BILLED BIRDS, OK DABBLERS. 307 



skim the surface, or dash horizontally after their prey in the 

 water in the manner of the divers, and not to those which 

 seek the bottom. A bird may get down several feet, or even 

 two or three fathoms ; but to descend to the depth of half a 

 mile, which is shallow compared with the profundity of some 

 seas, and feed there, is beyond the power of any known inha- 

 bitant of the air. The rocks, the gravel, and the sand, again, 

 are fitted only for birds that have hard and pointed bills. 

 Consequently the inland lakes and pools, the slow-running 

 rivers, and their estuaries, the accumulations of water in the 

 fens and marshes, and the level and oozy beaches where the 

 water is shallow, and yet does not generally clear away so 

 completely as to afford a proper pasture for the Grallae, are 

 the principal places where the dabbling birds are to be found. 

 As that marshy state of the country is seasonal, the birds 

 under consideration have seasonal migrations. Those migra- 

 tions, the numbers of the birds, and the times of their appear- 

 ance, of course, vary j but they are all subject to a more 

 extensive winter migration southward than the divers. The 

 reason is obvious ; they do not, generally speaking, get so far 

 to seaward as that line of green water which is so fertile in 

 the arctic sea ; and the inland lakes and also the shallows 

 become frozen much earlier in the season and much farther 

 to the south, than the open sea, or the deeper water. Even 

 where they do not freeze, the northern lakes become less 

 fitted for these birds in the winter. Their banks are at all 

 seasons less thick with vegetation than those of the waters in 

 warmer and more southerly places ; and the vegetation north- 

 ward is generally more frail, so that it is swept away by the 

 winds and floods early in the season ; hence, as the water is 

 exposed to the action of the wind, it lashes the banks like 

 an ocean in miniature ; and, though it has not the lofty 

 swell of the salt sea, it is, from its inferior specific gravity, 

 more brawling and broken ; so that long before its motions 



