782 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



barred and those of back and sides of neck with more yellow tips ; 

 under wing-coverts and axillaries mostly brown usually with some 

 whitish edgings and a few axillaries sometimes barred ; upper wing- 

 coverts without pale tips except usually some lesser with white 

 tips. Dark form. — Apparently as adult but browner, not so black 

 and with shorter tail and occasionally obscurely barred on under - 

 parts but sequence is very difficult to trace in dark form. Moult as 

 adult except that tail sometimes starts Aug. 



Third winter. — Much like adult but throat more barred and 

 with very little or no yellow ; centre of under -parts often ticked 

 dark brown ; flanks and tail-coverts more barred. Third summer. 

 — As adult but with some white edgings to under wing-coverts and 

 axillaries and often some barred black and white, lesser coverts at 

 point of wing often edged white, under and upper tail-coverts and 

 vent usually more mottled with white and often some barred ; 

 sometimes chin and throat heavily streaked blackish. Dark form. 

 — Like adult but under -parts, under wing-coverts and sometimes 

 some upper tail-coverts narrowly tipped buff. 



Measurements and structure. — $ wing 348-375 mm., tail (ad.) 

 central 190-225, outer 70-105 shorter, (juv.) central 130-152, outer 

 5-15 shorter, (1st summer) central about 25 longer than outer, 

 (2nd summer) central 40-70 longer, tarsus 48-56, bill from feathers 

 36-40 (12 adults measured). $ wing 340-373, tail : (ad.) central 

 165-215, outer 50-95 shorter, bill 35-40. Primaries : 1st narrow 

 and about two-thirds primary-coverts, 2nd longest, 3rd 5-15 mm. 

 shorter, 4th 20-35 shorter, 5th 40-60 shorter. Elongated central 

 tail-feathers usually twisted towards vertical in adults and 3rd 

 summer birds but sometimes not twisted even in adults, tips 

 rounded with obtuse point. Rest of structure as Great Skua. 



Soft parts. — Bill yellowish-brown, tip black ; legs and feet 

 (ad.) black with some grey on tarsus, (juv.) blue-grey with distal 

 half of toes and webs black ; iris (ad.) black-brown, (juv.) whitish. 



Characters. — No subspecies. Distinguished from other British 

 Skuas by wing and bill being smaller than Great, larger than Arctic 

 Skuas, no white showing beyond primary-coverts as in Great Skua, 

 adult having rounded and usually twisted central tail-feathers. 



Breeding-habits. — Little definite information available : less 

 sociable in habits than Great or Arctic Skuas, nests being placed 

 considerable distances apart. Nest. — Depression in mossy tundra. 

 Eggs. — Normally 2, olive or warm brown in ground-colour, blotched 

 and spotted blackish-brown. Average of 19 well authenticated 

 eggs, 64.06x44.8. Max.: 72.6x44.9 and 71 X 47. Min. : 57.2 X 

 43.6 and 66.1 X41.5 mm. Breeding -season. — Second half June and 

 early July. Incubation. — No reliable data. Single brooded. 



Food. — Where Terns and Gulls are at hand will force them to 

 disgorge food in flight. On breeding ground feeds largely on lem- 

 mings and will also capture fish and devour carrion, stranded fish, 



