216 ON THE NATURAL HISTORY OP THE NIGHTINGALE. 



greater part of Scotland, because, appearing as they do to migrate 

 almost exactly parallel to the lines of longitude, these would proba- 

 bly never find their way to land ; and this I consider to be the rea- 

 son why Nightingales are nowhere found, except as rare and acci- 

 dental stragglers beyond the third meridian of western longitude. 

 From other districts they are cut off by the character of the soil, as 

 they avoid everywhere both the rocky ground and fen. 



Futile experiment of Sir John Sinclair. — And here also we per- 

 ceive an additional cause of failure to the experiment, made upon a 

 large scale, by Sir John Sinclair. That gentleman, wishing to in- 

 troduce the species upon his estates (I rather think) in Caithness, 

 procured a considerable number of Nightingales' eggs, and placed 

 them in the nests of Robins, where the young Nightingales were 

 hatched and reared, and were afterwards observed about the place 

 till the usual season of migration, whefl they disappeared, and were 

 never afterwards seen in the neighbourhood. 



Beturn of young migratorij birds to their native place. — There is 

 even another consideration which may be mentioned here in con- 

 nexion with this circumstance. It appears, from the experiments 

 of Temminck and others, made however chiefly upon aquatic birds, 

 that the young of these (many of which require more than one 

 season to attain their mature plumage, and are, therefore, easily 

 distinguished) do not migrate either to the north or south over so 

 many degrees of latitude as the older individuals ; and although I 

 could furnish some decided and very remarkable instances of the 

 young of the small migratory land birds returning the following 

 spring to the place of their nativity, yet it is possible that the same 

 law which thus exists among migrant water-fowl, may also, to a 

 certain extent, prevail with them ; so that, although the young of 

 the preceding year will return to their native place when situate 

 within the southern or middle districts of the natural summer range 

 of their species, still they may not, perhaps, continue their journeys 

 to the extreme north. It is not unlikely, too, that these may 

 always have some tendency to settle in convenient localities, but 

 are generally driven off and prevented by the birds which have 

 already occupied them; and this is rendered, indeed, the more pro- 

 bable by the fact that, in many situations, no sooner is a Nightin- 

 gale captured in spring, than another immediately supplies its 

 place : yet this is not conclusive, for as migratory birds sing by day 

 before they have finally taken up their abode, we never can be sure, 

 for a certain time, that it is the same individual we hear on succes- 

 sive days; an experienced ear will, indeed, very frequently detect 



