. The story of the birds; . ilders have perhapsnever been colored or marked, but others doubtlessmay be blank by losing their family record. Amongthe colored eggs of many birds to-day there are tend-encies toward an occasional white egg, and in thebluebirds these are rather frequently found. It ispossible that, since their eggs are no longer more use-ful when colored than when plain, the bluebird ofthe very far future may lay a white egg, if it persistin hole building. If we had space some evidences could be citedthat the coloring and marking of eggs are compara-tively recent. It is shown by t
. The story of the birds; . ilders have perhapsnever been colored or marked, but others doubtlessmay be blank by losing their family record. Amongthe colored eggs of many birds to-day there are tend-encies toward an occasional white egg, and in thebluebirds these are rather frequently found. It ispossible that, since their eggs are no longer more use-ful when colored than when plain, the bluebird ofthe very far future may lay a white egg, if it persistin hole building. If we had space some evidences could be citedthat the coloring and marking of eggs are compara-tively recent. It is shown by the deposit of color inthe oviduct, occurring usually when the egg is lowdown only, and then upon the outer layers of theshell chiefly. In some grouses and ptarmigans thecolor can be readily rubbed off when the egg is firstlaid. On the other hand, in a few birds there is evi-dence which seems to show that there is a tendencytoward losing color. In the cormorants and similarforms, in cuckoos and others, the outer layer of the. Sparrow hawk, youn*,^, and nesting hole. THE MARKINGS AND SHAPES OF BIRDS EGGS. HQ shell is usually incomplete and uncolored, while thatbelow is a bluish green. Many of the hawk formsappear (as they have grown more arboreal in theirbuilding) to have a tendency to lose those strongmarkings, and to dilute the deep stains which charac-terize the eggs of their ancestral relatives, the vul-tures. So also the flycatchers usually lay stronglymarked eggs, but the Phoebes are only specked occa-sionally, and the least flycatchers are always whollywhite. Eggs frequently hint, though not always very re-liably, the kinship of the bird; and, strange to say,their very great variations may sometimes seem in-clined to point one way and sometimes the other. Infact, many of these variations must be the result of thedouble strain of kinship that comes into every crow blackbird lays two forms of eggs—onerather crowlike and one zigzagged, like those of theorioles. I
Size: 1246px × 2005px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectbirds, bookyear1897
