4] DISPERSAL AND MICRATION II5 



or 800 miles ' ; he also gives this distance as the one up to Avhich 

 he beheves frugivorous Birds have visited very many islands, carrying 

 germinable seeds in their viscera and consequentlv stocking these 

 islands with plants. 



Earlier, Darwin had similarly remarked [op. cit., pp. 326-7) : 



' after a bird has found and devoured a large supply of food, it is 

 positively asserted that all the grains do not pass into the gizzard for 

 twelve or even eighteen hours. A bird in this interval might easily 

 be blown to the distance of 500 miles, and hawks are known to look 

 out for tired birds, and the contents of their torn crops might thus 

 readily get scattered. Some hawks and owls bolt their prey whole, 

 and, after an interval of from twelve to twenty hours, disgorge pellets, 

 which, as I know from experiments made in the Zoological Gardens, 

 include seeds capable of germination. Some seeds of the oat, wheat, 

 millet, canary, hemp, clover, and beet germinated after having been 

 from twelve to twenty-one hours in the stomachs of different birds of 

 prey ; and two seeds of beet grew after having been thus retained for 

 two days and fourteen hours.' 



What a distance they cotdd have gone in a migrating Peregrine 

 Falcon ! 



(h) Mammals. These, among animals, stand next in importance 

 to Birds as disseminaters of plants. Except in the case of Fruit-bats, 

 which can transport seeds, etc., over stretches of sea much as Birds 

 do, their disseminative powers are confined to individual land-masses 

 — apart, of course, from traversable shallow or very narrow waters 

 or sea-ice in arctic regions (there are no land mammals in Antarctica). 

 The Mammals are important dispersal agents of many herbaceous 

 plants with small seeds, which they swallow with the foliage, etc., of 

 the plants they consume, and are also the main transporters of plants 

 with adhesive disseminules. Even though many herbivorous 

 Mammals eifect such thorough digestion that the vast majority of 

 seeds and fruits which thev take into their bodies are incapable of 

 germination after voiding, there are nevertheless plentiful instances 

 of disseminules being excreted unharmed, and we should always 

 remember the odd animal that dies suddenly, or is killed and eaten 

 by a predator. Ridley {op. cit., p. 336) remarks that, in the case of 

 stone-fruits, ' almost invariably the seeds pass through the intestines 

 of the animal, not only unharmed, but much benefited by the treat- 

 ment. Seeds so passed are known to germinate more quickly and 

 produce stronger plants than those which have not been swallowed 

 by bird or animal and acted on by the gastric or intestinal fluids.' 



