Page:Bird-lore Vol 05.djvu/105

 92 Bird-Lore

All przt-cocial birds are hatched with a growth of downy feathers , .. which. when they are dry, practically cover their body. (mm/1mm a/ . . . ' . . Most almcial blnlS are born essentially naked and do not hung at, t . B. [I leave the nest until they have acquired the nestling or If I.

Juvenal plumage. There are. however. numerous excep-

tions to this statement. For example, many species of the familv Alcidz (l’uﬂins. Murrelets. etc), the Petrels. Herons, Hawks and Owls are

WELLJ'URUED star or KED’H’IVUEI) mlacxuixn. Ax ALTRICIAL BIRD

llinxlewoml. K. J, May w, wa

more or less well covered with feathers at birth, but are then nevertheless comparatively helpless and spend some weeks in the nest.

The signiﬁcance of the condition of the young at birth is far-reaching, but, unfortunately, it is not as yet understood. It happens that most of the older or lower forms of birds, *that is, those birds nearest the reptilian type, whence, it is believed, all birds descended,—are prmcocial. On the other hand, all the higher birds, that is, those farthest from reptilian ancestors. are altricial. For example, among North American birds the Grebcs, Loons, Gulls. Terns, Ducks, Rails, Coots, Snipe, Plover and gallinaceous birds are pnecoeial, that is, their young run or swim shortly