PDF - Wallace Online

v THE PHILOSOPHY OF BIRDS' NESTS 103ants' nests, the soft materials of which they can easily hollowout.Many terns and sandpipers lay their eggs on the baresand of the sea-shore, and no doubt the Duke of Argyll iscorrect when he says that the cause of this habit is not thatthey are unable to form a nest, but that, in such situations,any nest would be conspicuous and lead to the discoveryof the eggs.' The choice of place is, however, evidentlydetermined by the habits of the birds, who, in their dailysearch for food, are continually roaming over extensive tidewashedflats. Gulls vary considerably in their mode ofnesting, but it is always in accordance with their structureand habits. The situation is either on a bare rock or onledges of sea- cliffs, in marshes or on weedy shores. Thematerials are sea-weed, tufts of grass or rushes, or the ddbrisof the shore, heaped together with as little order and constructiveart as might be expected from the webbed feet andclumsy bill of these birds, the latter better adapted for seizingfish than for forming a delicate nest. The long-legged broadbilledflamingo, who is continually stalking over muddy flatsin search of food, heaps up the mud into a conical stool, onthe top of which it lays its eggs. The bird can thus situpon them conveniently, and they are kept dry, out of reachof the tides.Now I believe that throughout the whole class of birdsthe same general principles will be found to hold good,sometimes distinctly, sometimes more obscurely apparent,according as the habits of the species are more marked, ortheir structure more peculiar. It is true that, among birdsdiffering but little in structure or habits, we see considerablebut we are now so welldiversity in the mode of nesting,assured that important changes of climate and of the earth'ssurface have occurred within the period of existing species,that it isby no means difficult to see how such differenceshave arisen. Simple habits are known to be hereditary, andas the area now occupied by each species is different fromthat of every other, we may be sure that such changes wouldact differently upon each, and would often bring togetherspecies which had acquired their peculiar habits in distinctregions and under different conditions.