THE SANDERLING. 125 



has been found, are peculiar in the set of their tides, and must 

 be the same in the substances (including among them a por- 

 tion at least of the food of the littoral birds) which those 

 tides waft along and deposit. 



The tides of the Channel and the British Sea meet on some 

 part of these shores, and the place, and also the time of their 

 meeting, varies with the state of the weather, so that the 

 point of confluence shifts along the coast, and the relative 

 turns of the two tides shift along with it, thereby producing 

 several alternations of flood in the time of one regular tide 

 of the open sea ; and, though the Channel tide generally 

 carries a portion of the swell of the Atlantic along the con- 

 tinental shore, which occasions the tumbling sea on the coast 

 of the Netherlands, and the great eddy which formed the 

 cod-fishery banks, yet the tide has much of an alternating 

 character upon the shore of England, and must keep the 

 small animals which are floodable by the water continually 

 in motion there, thus furnishing an abundant supply to those 

 birds that seek their food upon the beaches. Some circum- 

 stance of these tides, or of the matters which they deposit, 

 and the small animals which they foster on the shores, no 

 doubt determine the locality of the Kentish plover j in the 

 same manner as the drier atmosphere, the milder climate, 

 and the greater number of soft caterpillars, in the south-east 

 of England, determine the locality of the nightingale. A 

 very minute and accurate study of all the branches of natural 

 history is, however, necessary, in order to arrive at anything 

 like certain conclusions on the very curious, but, in the pre- 

 sent state of our knowledge, very vague subject of the local 

 distribution of birds. 



THE SANDERLING (Colidris arenario). 



The sanderling is another of our shore or beach birds, 

 agreeing with those already mentioned in the general form 



