1048 SYSTEMATIC SYNOPSIS. —PYGOPODES— GAVIjE. 



the base of the iuner. Tail short, but well formed, of 18-20 stiff featliers. Tibia with a very- 

 long apophysis ; patella rudimentary. Sternum M-ith long, broad, median projection backward 

 (metasternum), and shorter lateral processes. Skull with deep temporal fossse and supraorbital 

 depressions, separated by a well-marked sagittal crest, and small lacrymal bones iu close con- 

 nection with nasals. Spinal column with free vertebrae. Carotids double. Coeca and ambiens 

 present, accessory seraitendinosus absent; sternotracheal muscles symmetrical. Back spotted. 

 Head of adults never crested or ruffed, of young not striped. Loons are large heavy birds 

 with broad flattened body and rather long sinuous neck, abundant on the coasts and large in- 

 land waters of the Northern Hemisphere. They are noted for their powers of diving, being 

 able to evade the shot from a gun by disappearing at the flash, and to swim many fathoms 

 under water. Loons also share with Grebes the curious faculty of altering their specific grav- 

 ity at will, by inhaling or exhaling air, so that they can sink quietly down in the water without 

 diving, and swim with the body more or less submerged, but with head and part of the neck out 

 of water. They are migratory, breeding mostly in high latitudes, generally dispersed S. in 

 winter. They are prsecocial, and generally lay 2 dark-colored spotted eggs in a rude nest or 

 none by the water's edge. The voice is extremely loud, harsh, and resonant. Sexes alike; 

 9 smaller than ^ ; young and winter adults different from summer adults. There is but 

 one genus, with 5 species, all North American. 



CrA'VIA. (Ital. name of a Grull. As Lat. used by Moehring, 1752, for Gulls; by Brisson, 

 1760, for Gulls and the Noddy Tern; by Forster, Enchiridion, 1788, p. iiS, for the Loons, as 

 here applied ; by Boie, 1822, for certain Gulls ; by Gloger, 1842, and Naumann, 1834, for certain 

 Plovers ; by the A. 0. U. 1886-95, for the Ivory Gull : see Allen, Auk, xiv, July, 1897, p. 312, 

 and CouES, ibid. p. 313. In the plural, Gavice was used by Bonaparte, 1850-53, for an order 

 of birds equivalent to Longipennes and Tubinares, or Gulls and Petrels (including the genus 

 Chionis !), to which were added the Urinatores, or Loons, Grebes, and Auks. I now restrict 

 GavicE to the latter. See Newton, Diet. 1893, p. 310.) Loons or Divers. Characters as 

 above given for the family GaviideB. {Colymbus of all former editions of the Key. Urinator 

 of A. 0. U. 1886-95.) 



Analysis of Species and Varieties (Adtilts in summer). 



Head and neck black, with green, blue, and purple reflection, and patches of white streaks. 



Bill mostly or wholly black ; culmen, commissure, and gonys gently curved with slight gonydeal angle ; feathers 

 falling short of middle of nostrils; culmen 3.00 or less; gape 4.00 or more ; height of bill at nostrils usually 



under 1.00. Gloss of head and neck mostly green ; white spots of back nearly square imber 



Bill mostly yellow ; culmen nearly straight ; commissure and gonys straight with sharp gonydeal angle ; feath- 

 ers reaching middle of nostrils ; culmen about 3.75 ; gape about 5.00 ; height of bill at nostrils usually over 1.00. 



Gloss of head and neck mostly blue ; white spots of back longer than broad adamsi 



Top of head bluish-ash ; front of neck blue-black ; neck with white stripes. 



Larger: wing about 12.00 ; bill about 2 .50, stout, with convex culmen arcticus 



Smaller: wing about 11.00 ; bill about 2.00, slender, with straight culmen pacificus 



Throat and sides of head bluish-ash ; front of neck with red patch lumme 



Analysis of Species {Adults in winter and Young). 



Back with paler gray margins of the feathers and no spots. Wing 12.50 or more. 



Bill as above said for summer imber 



Bill as above said for summer adamsi 



Back uniformly dark or with gray margins (young); some spots on wing-coverts. Wiug 11.50-13.00. 



Larger, as above said arc/icus 



Smaller, as above said pacificus 



Back profusely spotted with white. Wing 11 50 or less lumme 



G. im'ber. (Danish imber; Swedish immer, emmer; Fferoic imbrim ; Icelandic himbrim; 

 English ember, imber, immer, etc. in composition M'ith goose. Fig. 711.) Common Loon. 

 Great Northern Diver. Imber Diver. Ember-goose. Adult (^ 9 > in summer: Bill 

 black, the tip and cutting edges sometimes yellowish. Feet black. Iris red. Head and neck 



