ALCIB^: AUKS. 797 



* 

 the end. Tarsus much abbreviated, comparatively stout, about three-fourths as long as middle 



toe and claw. Middle and outer toes nearly equal. Basal semipalmation of toes more exten- 

 sive than in PodMpes. Lobe of hind toe moderate. 

 853. P. podi'cipes. (For podicipes, see above.) PrED-BiLLED Grebe. Dabchick. Dippee. 

 DiEDAPPER. Waterwitch. Adult, breeding plumage : Bill light duU bluish, or bluish- 

 white, dusky on ridge or at tip, encircled with a broad black band. Iris brown and white ; 

 eyelids white. Feet greenish-black outside, leaden-gray inside. Frontal and coronal bristles 

 black. Crown, occiput, and neck behind, grayish-black, the feathers with sUghtly lighter 

 edges. Sides of head and neck brownish-gray. A broad black throat-patch, extending on 

 sides of lower mandible. Upper parts brownish-black, the feathers with scarcely lighter edges. 

 Primaries and secondaries chocolate-brown, the latter frequently with a white area on the inner 

 webs. Under parts ashy, washed over with silvery-gray, thickly mottled with dusky ; these 

 dark spots most numerous and evident on the pides. Lower belly nearly uniformly dusky. 

 Winter plumage : Bill light dull yellowish, without a dark band, more or less dusky on the 

 ridge. No gular patch. Crown and Occiput dusky brown. Upper parts with more evident 

 pale edgings of the feathers than in summer. Neck, breast, and sides, light brown, darker 

 posteriorly, where more or less conspicuously mottled with dusky. Under parts otherwise pure 

 silky- white, immaculate; lower belly grayish. Young-of-the-year : White gular patch in- 

 vaded by streaks of the brownish of the head, and the latter much streaked with white. 

 Dimensions: length about 13.00; extent 24.00; vidng about 5.00; bill along culmen 0.75 ; 

 along gape 1.30 ; height at nostrils 0.40 ; width 0.25 ; tarsus 1.50 ; middle toe and claw 2.15. 

 Varies greatly in size. Inhabits the greater part of S. and C. Am. and aU temperate N. Am. ; 

 the most abundant species of the family in Eastern U. S. 



63. Family ALCID-^: Auks. 



Feet palmate, three-toed (hallux wanting). Tarsi reticulate or partly scuteUate. Tibio- 

 tarsal joint naked. Claws ordinary. BiU of wholly indeterminate shape, often much as in 

 ColymbidcB or Podieipedidee ; often curiously shaped, with various ridges, furrows, or homy 

 protuberances. Tail perfect, of few feathers. Lores completely feathered. Nostrils wholly 

 variable in shape and position, naked or feathered. Legs .very variable. Coloration vari- 

 able ; head often with long curly crests. No tibial apophysis. Usually (always?) an anconal 

 sesamoid, sometimes double. Carotids usually double (single in AUe). Coeca coli pres- 

 ent; ambiens muscle present, accessory semitendinosus absent; oil-gland tufted. Palatal 

 structure sohizognathous ; nasal schizorhinal. Nature altricial and ptilopsBdic. Eggs few or 

 single, plain or variegated. The numerous species confined to the Northern Hemisphere. 



Birds of this family vrill be immediately recognized by the foregoing circumstances, taken 

 in connection with general pygopodous characters. Agreeing closely in essential respects, they 

 differ among themselves to a remarkable degree in the form of the bUl, with every genus and 

 almost every species ; this organ frequently assuming an odd shape, developing homy pro- 

 cesses, showing various ridges and furrows, or being brillj^ntly colored. It is the rule that 

 any soft part that may be observed on the bill will finally become hard, or form an outgrowth, 

 or both ; and such processes, in some cases at least, are temporary, appearing only during the 

 breeding season. 



The last sentence, reprinted as it stands in the original edition of the Key (1872) hints at 

 the extraordinary changes undergone by the bill in several genera oi AkHdce, so ably elucidated 

 in 1877 and 1879 by L. Bureau, who showed that in many species parts of the homy covering 

 of the biU are regularly shed or mwblUd, in a manner analogous to the casting of deer's antlers, 

 quite as shown by E. Eidgway in the case of our White Pelican, which drops the "centre- 

 board." In the Common Puffin, for example, no fewer than nine pieces of the bill fall of 



