250 



ISLAND LIFE. 



[part II. 



Birds as Seed-carriers. — The great variety of fruits that are 

 eaten by birds afford a means of plant-dispersal in the fact that 

 seeds often pass through the bodies of birds in a state well-fitted 

 for germination ; and such seeds may occasionally be carried long 

 distances by this means. Of the twenty-two land-birds found in 

 the Azores, half are, more or less, fruit-eaters, and these may have 

 been the means of introducing some plants into the islands. 



Birds also frequently have small portions of earth on their 

 feet ; and Mr. Darwin has shown by actual experiment that 

 almost all such earth contains seeds. Thus in nine grains of 

 earth on the leg of a woodcock a seed of the toad-rush was 

 found which germinated ; while a wounded red-legged partridge 

 had a ball of earth weighing six and a half ounces adhering to its 

 leg, and from this earth Mr. Darwin raised no less than eighty- 

 two separate plants of about five distinct species. Still more re- 

 markable was the experiment with six and three-quarter ounces 

 of mud from the edge of a little pond, which, carefully treated 

 under glass, produced 537 distinct plants 1 This is equal to a 

 seed for every six grains of mud, and when we consider how 

 many birds frequent the edges of ponds in search of food, or 

 come there to drink, it is evident that great numbers of seeds 

 may be dispersed by this means. 



Many seeds have hispid aw^ns, hooks, or prickles which readily 

 attach them to the feathers of birds, and a great number of 

 aquatic birds nest inland on the ground ; and as these are pre- 

 eminently wanderers, they must often aid in the dispersal of 

 such plants.^ 



^ The following remarks, kindly communicated to me by Mr. H. N. 

 Moseley, naturalist to the Challenger, throw much light on the agency of 

 birds in the distribution of plants : — ''Grisebach (Veg. der Urde, Vol. II. p. 

 496) lays much stress on the wide ranging of the albatross (Diomedea) 

 across the equator from Cape Horn to the Kurile Islands, and thinks that 

 the presence of the same plants in Arctic and Antarctic regions may be 

 accounted for, possibly, by this fact. I was much struck at Marion Island 

 of the Prince Edward group, by observing that the great albatross breeds 

 in the midst of a dense, low herbage, and constructs its nest of a mound 

 of turf and herbage. Some of the indigenous plants, e.g. Acsena, have 

 flower-heads which stick like burrs to feathers, &c., and seem specially 

 adapted for transportation by birds. Besides the albatrosses, various 

 species of Procellaria and Puffinus, birds which range over immense dis- 



