INTRODUCTION. XIX 



The nature of the country, whether prairie or wooded, rocky and 

 barren, or marshy, must also be taken into account in all speculations 

 on the distribution of the feathered tribes. Several of the Grallatores, 

 for instance, that feed by thrusting their bills into soft marshy soil, 

 frequent the Saskatchewan prairies only in spring, and as soon as the 

 warm and comparatively early summer renders the soil dry and unfit to 

 yield them support, they retire to their breeding-quarters in the Arctic 

 lands. There, the frozen sub-soil acted upon by the rays of a sun 

 constantly above the horizon, keeps the surface wet and spongy 

 during the two short summer months which suffice these birds for 

 rearing their young. This office performed, they depart to the south- 

 ward, and halt in the autumn on the flat shores of Hudson's Bay, 

 which, owing to accumulations of ice drifted into the Eay from the 

 northward, are kept in a low temperature all the summer, and are 

 not thawed to the same extent with the more interior Arctic lands 

 before the beginning of autumn. They quit these haunts on the 

 setting in of the September frosts, and passing along the coasts of the 

 United States, retire within the Tropics in the winter. 



Many species, which are purely summer visiters of the high lati- 

 tudes, are resident within certain parallels of the United States, de- 

 tachments advancing to the north in the spring for the purpose of 

 rearing their young and retiring to the south of the resident stations 

 in winter. It is obviously very difficult to ascertain whether the 

 individuals of these species which breed in the higher latitudes are 

 the same that retire farthest southwards in winter, those remaining 

 in the intermediate districts in winter being the pairs which bred 

 there, though from analogy we are led to think that such is the case. 

 Of the strictly resident birds in Europe it is known that many (the 

 House-Sparrow, for instance) shelter themselves in winter in their 

 nests and summer haunts ; and of the migratory ones, the same pair 

 have been observed to build several successive seasons in the same 

 spot. Some species seem to claim a right of property within a certain 

 beat, chasing away with great pertinacity all the other birds that they 

 can master. In the instance also of the Falconidce and some other 



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