308 NATATORES. 



are sealed up by the frost, it ceases to afford either shelter or 

 food for the dabbling birds. 



As is the case with that division of the Grallae which 

 follow the progress of seasonal flooding and inundation in 

 the warmer latitudes, this division of the swimming birds 

 is adapted for performing migration on the wing, and by 

 long and lofty flights. From their size and weight, and 

 their wings being more the instruments of migrations than 

 those of habitual use in the procuring of their food, none of 

 these birds fly with so much rapidity as the swallows, or 

 probably some of the other migrants ; but still their speed 

 compared with that of quadrupeds along the ground is very 

 rapid. The wild swan proceeds at the rate of at least twenty 

 miles an hour, and perhaps that of the common wild goose 

 is not much slower. Such are a few of the more general 

 characters, briefly and imperfectly sketched ; but still, per- 

 haps, sufficient to afford at least some general idea of the 

 place which the birds fill in the general system and economy 

 of nature. 



We may, however, farther remark in passing, that, in so 

 far as the nests and breeding places of these birds are known, 

 they are much more prolific than the divers. The number of 

 eggs varies considerably in the different species. In some, as 

 in the wild swan, it is not more than five, while in other 

 species it is as many as fifteen or sixteen ; but taking the 

 average of the whole, it may be estimated at about eight or 

 ten. That might be expected, as both the haunts and habits 

 of the birds expose them more to casualties and to enemies 

 than those of the divers. 



In giving a short notice of the genera, we shall omit the 

 domesticated ones, as not belonging to the wild nature of the 

 country. 



