214 LIFE : OUTLINES OF GENERAL BIOLOGY 



Pcntland Hills; (2) they were protected and encouraged by the 

 proprietor, who fed his young pheasants on the gulls' eggs; (3) they 

 nevertheless flourished, the last clutch being always left to hatch; 

 and (4) they increased enormously till (ii>97) there were 1,500-2,000 

 pairs of birds. The grouse that used to frequent the heather disap- 

 jxared. Hut with the extension of the gullery the vegetation 

 (5) underwent a noticeable change, the heather being replaced by 

 abundant coarse grass, which was cut for hay, then by a dense 

 growth of rushes, both (6) becoming almost choked by a forest of 

 docks. \\hereujx)n the villagers, angry at the destruction of their 

 hay-crop, made persistent raids on the gullery, and the proprietor, 

 regretful at the disappearance of grouse, ceased to protect the 

 gulls for his pheasants. In 1917 not more than thirty pairs nested, 

 where a few years before there had Ixn-n some two thousand pairs. 

 Then the vegetation began to change back again (7), the docks and 

 rushes giving way to rough grass and even to heather. Finally, the 

 grouse began to return! 



KoADS AND HoRSKS. — We have referred to the trimming and 

 broadening of roads, with the resulting decrease of shelter, but there 

 are two other points to be considered. The modern road adapted to 

 motor-traffic has in many cases something in the way of tar- 

 macadam or asphalting; and it is generally believed that the wash 

 after rain is detrimental to the small animals in ditches and stream- 

 lets, and directly or indirectly to trout and salmon in the adjacent 

 rivers. This may possibly mean the destruction of the young stages 

 of some injurious insects, but it also implies a reduction of part of 

 the food-supply of insectivorous birds. It may be replied, however, 

 that this will Ix* far more than outweighed by the augmentation of 

 insects im])lit'd in the increase of farm-land with its abundance ot 

 suitable food-plants. The issues are so manifold and criss-cross that 

 it is ne.xt to im|X)ssihle to predict the final result of more or less 

 necessary changes; but the general projX)sition is this, that extensive 

 crops aiTord suixrahundant food to inst^ct-pests — such as turnip 

 green-fly. turnij> moth, turnip saw-fly, turnip flea-beetle and dia- 

 mond-barked moth; that a promi.seful counteractive of these 

 plagues is the multiplication of the birds which prey upon them; 

 and that this implies a conservation of suitable shelter and cover. 



The numlxTs of field-ins<'cts must be incalculably greater than in 

 old days, when agricultural ojxTations were le.ss extensive; and that 

 ought automatirally to mean more birds. Yet it may sometimes mean 

 a disproi)ortionate increas*- of certain tyix«s of bird, such as starlings, 

 which arc apt to drive away .smaller insect-eaters, like wrens, robins, 

 and warblers, whicli, moreover, are more dejx^ndent on the minor 

 shelters like hedgerows, the starlings mostly roosting in trees. 



Some birds, that are largely .seed-eaters, like the finches, may be 

 beneficial to agriculture, inasmuch as they feed their young on 



