190 THE BOOK OF THE OPEN AIR 



to many enemies, and who are speci- even a small one. Accidents of local- 

 ally liable to human molestations. ity appear to react on avine fecundity 

 One great principle stands out clearly with extreme rapidity, as might be 

 from these inquiries that birds in- expected when generations are counted 

 variably reproduce their kind by an by years. Where a locality changes 

 instinct of reproduction, and not as a its character from rural to suburban 

 mere necessary appendage to sexual or urban in a few years, for instance, 

 intercourse. Any minor principles are we do not find the birds that formerly 

 more or less latent, and would repay laid large clutches in it continuing to 

 deeper inquiry. lay large clutches ; but on the con- 

 trary we find them within three years 

 accommodating the number of their eggs 



IF it is established that all birds have to the food supply. This accommo- 

 a strong parental instinct, as distin- dation cannot of course be deliberate 

 guished from the purely sexual attrac- in the parents, but must be due to 

 tion, and that this parental instinct impoverished physical condition. They 

 is so strong that neither eggs nor a are less well nourished as a district 

 callow youngster or so can satisfy it, once adapted to their habits and 

 but every pair labours on determinedly needs ceases to be so adapted ; and a 

 to raise the maximum number of greater expenditure of labour becomes 

 matured youngsters, it remains to necessary to procure what food is 

 ascertain how and why the members obtainable ; and so they have a smaller 

 of a single species differ in the extent store of physical strength, and much 

 of their fecundity. Not only do we find of it is exhausted in the work that 

 different normal clutches as between comes before nesting, 

 species and species, but we find vary- The possibility, and later the cer- 

 ing clutches between different members tainty, of these differences, and their 

 of the same species, and that often in origin, was early brought under my 

 close neighbourhood. The accidents notice, seeing that for several years 

 and conditions of locality would appear I resided for alternate periods in the 

 to be the determining factor, some bleak and smoky outskirts of a north- 

 districts being suited to the successful ern manufacturing town, and on 

 rearing of a large brood, and others ad- the edge of some of the richest land 

 verse to a particular species maturing in the fertile western counties. Orni- 



