36 Introduction. 



and swampy spots, which are the especial habitat of the whole 

 order of waders. 



We come now to the last order, ' Natatores,' the ' swimmers/ 

 whose name bespeaks them as denizens of the ocean and lake. 

 Kemarkable for their facilities of swimming and diving, and for 

 their powers of submergence often for a considerable time, many 

 families of this order procure their food entirely in the water. 

 For this purpose the beaks of some are armed with sharp hooks 

 or teeth, as in the mergansers ; some are straight, sharp, and 

 compressed, as in the divers, auks, and gulls; others again, 

 which rarely dive and in diet are graminivorous as well as 

 granivorous, are furnished with very broad and much de- 

 pressed mandibles : all are peculiarly formed for holding 

 securely their food, which is frequently of a slimy and slippery 

 nature. 



We have now run rapidly through the several orders and 

 tribes, paying attention to the general formation of the beak in 

 each, and have seen how strong a resemblance usually pervades 

 all the families contained in them ; we cannot fail to have 

 observed at the same time how admirable in every case was the 

 construction for attaining the desired end. There are still some 

 particular species which exhibit so remarkable a peculiarity in 

 this organ that I am unwilling to pass them by. 



One of the most curious is the Crossbill, a bird familiar to 

 most persons, as it occasionally, though not periodically, visits 

 us in considerable numbers. Its name at once points out what 

 some persons (and these naturalists of eminence, including the 

 zealous but often inaccurate Buffon) have been pleased to call 

 its natural defect, but which is now pretty generally considered 

 a most admirable provision of nature. These birds inhabit 

 extensive forests of pines and firs, the seeds of which form their 

 chief food ; but to arrive at these, a peculiar instrument is 

 necessary. To this end, the mandibles (which in young birds in 

 the nest are of the ordinary form) become elongated and cross 

 one another at the tip to a considerable degree ; in some speci- 

 mens the upper mandible is curved to the right, the lower to 



