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Show 250 ISLAN 0 LIFE. (pART II, Bi?'ds as Seed-ca?Tiers.-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 w~ll-fitted for germination; and such seeds may occasionally be. earned lo~g distances by this means. Of the twenty-two land-brrds found m the Azores, half are, more or less, fruit-eaters, and these may have been the means of introducincr some plants into the islands. b • Birds also frequently have small portions of earth on thmr 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 eightytwo separate plants of about five distinct species. Still more remarkable 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! 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 rna y be dispersed by this means. Many seeds have hispid awns, 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 preeminently wanderers, they must often aid in the dispersal of such plants.1 1 The following remarks, kindly communicated to me by Mr. H. N. Moseley, naturalist to the Challengm·, throw much light on the agency of birds in the distribution of plants:-" Grisebach (Veg. der· Erde, 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. Acrona, have flower-heads which stick like burrs to feathers, &c., and seem specially adapted for transportation by birds. Besides the albatrosses, various species of Proeellaria and Puffinul'l, birds which range over immense dis- CUAP. XII.] TilE AZORES. 251 Pacil,it~ies jo1· Dispenal oF Azo?'ean Plants No~" · th 'J · .- " rn e course of very long ~~riods of time the various causes here enumerated would be s~ffiCient to stock the remotest islands with vegetation, and a consrderable part of the Azorean flora appears well adapted t~ be so conveyed: Of the 43D flowering-plants in Mr. Watson's hst, I find t~at about forty-five belong to genera that have either pappus or: wmged seeds; sixty-five to such as have very minute ~:;eeds; thrrty have fleshy fruits such as are greedily eaten b b' d . lh l'. y rrs, sev~ra ave nsprd seeds; and eighty-four are glumaceous plants, w~rch are all probably well-adapted for being carried partly by wmds and ~artly by currents, as well as by some of the other causes mentwned. On the other hand we have a very suagestive fa?t in the absence from the Azores of most of the trees and shrubs ~rth large and heavy fruits, however common they may be in Euro~e. Su~h are oaks, chestnuts, hazels, apples, beeches, alders, and firs; whrle the o~ly trees or brge shrubs are the Portugal :aural, myrtle, laurestm~s, ~lde~·, Laurus canariensis, Myricafaya, d,nd a dou?tfully pecuhar JUmper-all small berry-bearers, and therefore hkely to have been conveyed by one or other of the modes suggested above. tances ma?', I think, ha~e played a great part in the distribution of plants, and especwll~ acc.ount, m some measure, for the otherwise difficult fact (when ~ccurnng m the tropics), that widely distant islands have similar mountam plants. The Procellaria. and Puffinus in nesting, burrow in the ~Tound, ~s far as} ha':e se~n choosing often places where the vegetation 1s the thwkest. I he bnds m burrowing get their feathers covered with ve~·etable mot~ld, which must include spores, and often seeds. In high latitude~:; the ~uds often b.urrow nea1: the sea-level, as at Tristan d' Acunha or I~erguelen s L.and, but m the tropics they choose the mountains for their ~,~sti~~·-place (F1~~ch an~ Hartlaub, Om. der Viti- und Tonga-Inseln, 1867, Eml01tun~ p. xvm). 'I~~s, JJujjinus rnegasi nests at the top of the Korobasa b~sa5.a mountam, VIti Levu, fifty miles from the sea. A Procellaria breeds m hke man.ner in the high mountains of Jamaica, I believe at 7,000 feet. Peale descnbes the same habit of P1·ocellaria 1·ostrata at Tahiti, and I saw :he .burrow~ myself amidst a dense growth of fern, &c., at 4,400 feet elevatiOn m that Island. Phaethon has a similar habit. It nests at tl crata of Kilauea, Hawaii, at 4,000 feet elevation, and also high up in Tahi;~ In order to account for the tra~sportation of the plants, it is not of course necessary that the ~arne species of Procellaria or Diomedea should now range bet':ee~ the dis~ant ~oints where the plants occur. The ancestor of the no:v differ~ng speCies m1ght have carried the seeds. The range of the genus IS sufficient.'' |
