468 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



especially are very worn and moult to 2nd winter begins. Subse- 

 quent plumages apparently like adult. 



Measurements and structure.— $ wing 340-380 (one 408) mm., 

 tail 54-73, tarsus 76-98, bill from nostril 58-70 (12 measured). ? 

 wing 330-385, bill 53-67. Primaries : 1st very small and hidden 

 by primary-coverts, 2nd longest, 3rd as long or 1-5 mm. shorter, 4th 

 12-20 shorter, 5th 30-45 shorter, 6th 50-65 shorter ; outer primaries 

 sharply attenuated at tips but not definitely emarginated, second- 

 aries short, tips broad and notched. Tail short, much rounded (fan 

 shaped), 18 or 20 feathers, rather stiff, tips rounded. Upper and 

 under tail-coverts almost as long as tail. Bill very strong and 

 compressed, tapering to sharp point, upper mandible with upper 

 line descending gradually to tip, sides rather rounded, gonys sloped 

 upwards and tip of under mandible finer than that of upper. 

 Nostrils small, slit-like with tooth-shaped projection about centre. 

 Most of tibia enveloped by skin and legs thus inserted very far 

 back. Tarsus short and extremely compressed. Three toes long and 

 webbed, hind toe minute and elevated ; claws convex, rounded 

 and rather nail -like. 



Soft parts. — Bill in winter pale grey (juv. paler more bluish - 

 white), ridge of upper mandible blackish-slate extending over sides 

 to nostrils, tip horn -colour, in summer bill blacker ; legs and feet 

 (ad.) outside nearly black, inside very pale grey, webs same with 

 flesh-coloured centres, (juv.) paler, outside dusky, inside milky 

 blue-white ; iris (ad.) wine-red, (juv.) red-brown. 



Characters. — C. i. elasson (western N. America) stated to be 

 smaller requires confirmation. For differences of G. adamsii see under 

 that species. Much larger size distinguishes it from other Divers. 



Field -characters. — Exclusively aquatic, Divers are in Britain 

 mainly marine, but inland lakes are resorted to in nesting season 

 and casually at other times. In swimming and diving they equal 

 if not excel Grebes, from which they differ in larger size, bulkier 

 bodies — carried higher when swimming — stout necks and lack of 

 extravagant tippets and ruffs in breeding-season. All are loquacious 

 in spring and summer, uttering loud uncanny wails and hoarse 

 barking cries. Breeding dress of Great Northern differs from that 

 of Black-throated in throat-band and collar, profuse white speckling 

 of entire upper-parts and absence of slate-grey crown and hind- 

 neck. In winter plumage the two hardly differ except in size and 

 relative length and stoutness of bill, characters not always reliable 

 in the field. Wailing cry of Great Northern is described as a 

 " loud blood-curdling scream." Other notes are a loud resonant 

 " hooo-hoo-hoo-hoo " (Jourdain) and a sharp bark, " yap, yap, 

 yap " (Knox). 



Breeding-habits. — Met with on larger sheets of water and lakes 

 where water is deep. Nest. — In Iceland little more than a flattened 

 spot on tussock close to water or on island, but in Canada often a 

 big heap of vegetable matter in shallow water. Eggs. — 2, ground- 



