. A history of birds . nus Guttera. The pheno-mena here exhibited appear hitherto to have been passed withoutcomment, yet it is certainly remarkable that this keel, elsewhereamong birds a thin plate of bone, should in these Swans andCranes have developed into a cavernous receptacle, involvingalso the body of the sternum forming the roof of this are the factors which have brought about the formationof this curious chamber ? The theory of natural selection hereseems inadequate; while the theory of mutation involving thesympathetic variation of two such dissimilar structures seems nomo
. A history of birds . nus Guttera. The pheno-mena here exhibited appear hitherto to have been passed withoutcomment, yet it is certainly remarkable that this keel, elsewhereamong birds a thin plate of bone, should in these Swans andCranes have developed into a cavernous receptacle, involvingalso the body of the sternum forming the roof of this are the factors which have brought about the formationof this curious chamber ? The theory of natural selection hereseems inadequate; while the theory of mutation involving thesympathetic variation of two such dissimilar structures seems nomore helpful. For the capture of ants and other insects the Woodpeckershave developed a protrusible tongue—agreeing therein withmany ant-eating mammalia—and powerful salivary , without any such elaborate apparatus one of the King-fishers {^Halcyon cyanoleucus) of Liberia, which, after the fashionof his people, is almost tongueless, contrives to subsist on antswithout any special apparatus for their capture!. 6*^ Coverts III. 46A The upper surface of the wing of a Little Stint {Tringa miniita) toshow (a) the difference between the distal and proximal overlap-theformer shown by the major, the latter by the median coverts—and {b) the tault-incr which results in the formation of an intercalary row m diastataxic wmgs.° B, Upper surface of a portion of the forearm of an Owl to show the diasta-taxic condition of the wing. ADAPTATIONS 409 Here again is another instance of apparent over-elaborationin Nature. We say apparent advisedly, for the fact that so manywidely different creatures have developed a highly complexlingual mechanism for the capture of insect food shows thatthese exceptions require further study. By way of contrast we may site the case of the Red-headedWoodpecker {Melanerpes erythrocephald), which, like its con-geners, possesses a protrusible tongue ostensibly for the capture ofinsect prey, yet lives at any rate very largely, on eggs of otherbirds, even e
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbirds, bookyear1910
