BILLS OF THE CONIROSTRES. 185 



be expected. In tropical countries, the vegetation of 

 trees may be said to be constant, and the ground 

 vegetation is in a great measure propagated by bulbs, 

 or, at all events, the seeds of herbaceous plants do 

 not strew the ground there either so numerously, or 

 for such a length of time, as they do in regions where 

 the winter is more decided. There is thus not much 

 food for, at least the ground species of the Conirostres, 

 in tropical climates, and where they are found, they 

 are not so migratory in their habits as the soft-billed 

 birds. In such climates as that of England, their 

 grand feeding time is in winter, because the fields 

 are then covered with seeds, which are softened and 

 sweetened by the action of the weather, but have not 

 begun to sprout; and perhaps there is no race of 

 wild animals so serviceable to cultivation in such 

 climates as these birds. They come in vast crowds, 

 and clear the stubble field of the seeds of weeds, 

 which, if they were to spring up, as of course they 

 would do, if not gathered by the birds, would com- 

 pletely choke the crops in the following season. 



The bills of all these birds are thick and strong, 

 enlarged at the base, sharp at the tip, and the man- 

 dibles are often fortified by a margin, which, acting 

 upon the tough rinds of seeds, bursts them, and 

 extracts the farinaceous part, which is much more 

 readily and effectually done by the flat grinding 

 margins of the bill than it would be by sharp edges. 

 The different effect of these two kinds of form in 

 effecting this purpose may \>e perceived by any one 

 who tries to crack a nut with a pair of scissors, and 

 another with a pair of nut-crackers of the same lever- 

 power. 



The birds which have those bills do not feed ex- 

 clusively, or at all times, upon seeds. Indeed, it will 



