THE WHISKERED TERn! 691 



brighter than C. niger and leucopterus) ; rump and upper tail-coverts 



ash-grey, latter with faint whitish tips ; ear -coverts blacker than 



adult ; whole under -parts white ; 



tail-feathers pale slate-grey with 



tips edged pale buff and subtermi- 



nally black-brown ; wing-feathers 



as adults but tips rather darker, 



innermost secondaries as scapulars ; 



greater and median coverts slate - 



grey faintly tipped pale yellowish - 



buff with a small brownish subter- BiU of the Whisl?m . d Tern 



minal mark ; lesser coverts slate- (cnudonias i. uucopareim). 



grey with brownish centres. 



First winter. — Like adult winter except for brown tips of 

 unmoulted juvenile tail-feathers and innermost secondaries and 

 often a few brown feathers on crown and much-worn wing-coverts. 

 The juvenile body-plumage and central tail-feathers are moulted 

 July-Oct. but not rest of tail nor wing-feathers nor wing-coverts. 

 First summer. — A complete moult takes place Ap.-June. New 

 plumage apparently like adult summer. 



Measurements and structure. — £ wing 232-250 mm., tail : outer 

 feather 83-90, central 64-73, depth of fork 12-22, tarsus 22-25, 

 bill from feathers 30-34 (12 measured). $ wing 230-242. Primaries : 

 1st pointed, narrow and about two-thirds primary-coverts, 2nd 

 longest, 3rd 8-12 mm. shorter, 4th 22-30 shorter, 5th 35-50 shorter. 

 Rest of structure as Black Tern, but bill deeper and rather thicker 

 and gonys shorter with sharper slope ; webs between toes more 

 deeply incised. 



Soft parts. — Bill dark crimson ; legs and feet crimson (juv. red- 

 brown) ; iris red-brown. 



Characters and allied forms. — G. I. indicus (India) is smaller 

 C, I. swinlioei (S. China) is like last but throat usually whiter 

 C. I. fluviatilis (Australasia) is paler than others ; C. I. delalandei 

 (S. Africa) is decidedly darker than other forms. In summer vhite 

 stripes on sides of head and in winter and juvenile absence of brown 

 patches on sides of breast and larger bill distinguish Whiskered from 

 other Marsh-Terns. 



Breeding-habits. — Nests in colonies in shallow water, marshes, 

 lagoons, etc. Nest. — More carelessly built than that of Black Tern, 

 often merely a few rushes or weeds floating on water -surface where 

 some vegetation is growing, such as rushes. No definite cup. Eggs. — 

 Normally 3, sometimes 2, and rarely 4 ; ground generally bluish - 

 green, but sometimes stone -grey, ochreous, or pale brownish, 

 spotted or blotched with blackish-brown and ashy-grey, but less 

 heavily than Black Tern. Average of 100 eggs, 39.2 X 28.4. Max. : 

 44x27.6 and 40.2x30. Min. : 34.9x27.7 and 43.1x26.3 mm. 

 Breeding -season. — Latter half May and early June in south Spain. 



