282 FACULTIES OF BIRDS. 



rence of the periods at which the moult takes place 

 in the old and young- birds ; and this also appears 

 to be the cause that the flocks composed of adult 

 individuals migrate to a much greater distance, 

 whether in autumn or at their return in spring, than 

 the bands composed of young ones, which do not in 

 either season extend their journey so far. The 

 plumage of these birds being still incomplete, and 

 the colours not fixed, they generally take one or two 

 years before they are in a state for breeding. They 

 then choose those places where adults of their own 

 species do not build their nests, the latter always 

 expelling them from the districts which are to give 

 birth to a new progeny. When the old ones extend 

 their journey to the arctic regions, those of one or 

 two years old are found in the middle countries of 

 Europe; and when the old ones choose the tempe- 

 rate climates, the young ones remain in the south, or 

 at farthest do not pass the seas which separate 

 Europe from the northern parts of Africa countries 

 in which the greater part of the larger species of our 

 migratory birds, that do not perfect their growth 

 within the first year, choose to reside in winter. It 

 is from these countries, or the numerous islands of 

 the Archipelago, and those of the Mediterranean 

 and the Gulf of Venice, that they set off on their 

 return in spring. Numerous flocks are then seen 

 on all our southern coasts, especially where the sea 

 forms gulfs, such as the Archipelago, the Adriatic 

 Gulf, and those of Genoa and Lyons. These meet- 

 ings continue eight, ten, or at most fifteen days ; in 

 which time the passage of those countries is com- 

 pleted. The routes taken by our marsh and water 

 birds depend entirely on the course of the rivers 

 arid the direction of the great lakes. As the waters 

 are to supply each species with its proper food, they 

 seern to be impelled by a wonderful instinct, to 



