88 A HISTORY OF 



retreat. When the whole family is completely plumed, and capable 

 of avoiding danger by flight, they are then led forth when the weather 

 is fine, and taught the paternal art of providing for their subsistence. 

 They are led to the places where their food lies ; they are shown the 

 method of discovering or carrying it away; and then led bark to the 

 nest for a day or two longer. At length, when they are completely 

 qualified to shift for themselves, the old ones take them abroad, and 

 leading them to the accustomed places, forsake them for the last time, 

 and all future connexion is ever at an end. 



Those birds which are hatched and sent out earliest in the season, 

 are the most strong and vigorous ; those, on the other hand, that have 

 been delayed till the midst of summer, are more feeble and tender, 

 and sometimes incapable of sustaining the rigours of the ensuing win- 

 ter. Birds themselves seem sensible of this difference, and endeavour 

 to produce early in the spring. If, however, their efforts are ob- 

 structed by having their nests robbed, or some similar accident, they 

 still persevere in their efforts for a progeny ; and it often happens that 

 some are thus retarded till the midst of winter. What number of eggs 

 any bird can lay in the course of a season is not ascertained ; but this 

 is true, that such as would have laid but two or three at the most, if 

 their nests be robbed, or their eggs stolen, will lay above ten or twelve. 

 A common hen, if moderately fed, will lay above a hundred from the 

 beginning of spring to the latter end of autumn. In general, however, 

 it obtains, that the smallest and weakest animals are the most prolific, 

 while the strong and rapacious are abridged by sterility. Thus, such 

 kinds as are easily destroyed, are readily repaired ; and nature, where 

 she has denied the power of resistance, has compensated by the ferti- 

 lity attending procreation. 



Birds, in general, though they have so much to fear from man and 

 each other, are seldom scared away from their usual haunts. Although 

 they be so perfectly formed for a wandering life, and are supplied with 

 powers to satisfy all their appetites, though never so remote from the 

 object, though they are so well fitted for changing place with ease and 

 rapidity, yet the greater number remain contented in the districts 

 where they have been bred, and by no means exert their desires in 

 proportion to their endowments. The rook, if undisturbed, never de- 

 sires to leave his native grove ; the black-bird still frequents its ac- 

 customed hedge ; and the red-breast, though seemingly mild, claims a 

 certain district, from whence he seldom moves, but drives out every 

 one of the same species from thence without pity. They are excited 

 to migration by no other motives but those of fear, climate, or hunger. 

 It must be from one of these powerful motives that the birds, which 

 are called birds of passage, every year forsake us for some time, and 

 make their regular and expected return. 



Nothing has more employed the curiosity of mankind than these 

 annual emigrations; and yet few subjects continue so much involved 

 in darkness. It is generally believed, that the cause of their retreat 

 from these parts of Europe, is either a scarcity of food at certain sea- 

 sons, or the want of a secure asylum from the persecution of man 

 during the time of courtship and bringing up their young. Thus the 

 starling, in Sweden, at tne approach of winter, finding subsistence, no 



