BLACK TERN. 255 



example has occurred in West Africa, in the Cameroons. It is not known 

 that the Black Tern visits any of the Atlantic islands, but on the continent 

 of America a form occurs so nearly allied as to be doubtfully distinct *. 

 Sterna nigra surinamensis is, as a rule, somewhat darker and browner on 

 the underparts than European birds, but intermediate forms occur which 

 connect the two subspecies together. The American form breeds across 

 the continent, from South Alaska to South Canada, ranging as far south 

 as the Northern United States. It passes through the Southern States on 

 migration, and winters in Mexico, the West Indies, Central America, and 

 the northern portions of South America. 



It is not known that the Black Tern winters in any part of Europe ; it 

 arrives late in spring, and retires early in autumn. It makes its first ap- 

 pearance in Spain late in April, and Irby noticed numbers crossing the 

 Straits of Gibraltar on the 16th of May. It passes at once to its breeding- 

 grounds, reaching Denmark late in May. The return migration begins 

 late in July, it passes through France in August, and recrosses the Straits 

 in September and October. 



The Black Tern is rarely seen on the sea-coast ; it is essentially a lake- 

 bird, and prefers such as are full of beds of reeds and rushes. It delights 

 in large ponds full of horsetails (Equisetum) , and sheets of water sprinkled 

 over with water-lilies and different species of pond-weed (Potamogeton) . 

 It is one of the most gregarious of birds, and one of the most graceful on 

 the wing. The flocks of these birds, which skim like Swallows over the 

 water, often hovering like Kestrels over a luckless little fish, add a 

 wonderful charm to the landscape, whether it be near the lakes on the 

 sandy heaths of South Holland, or the floating islands of the lagoons on 

 the Pomeranian coast, or the marshes not far from Copenhagen, or the 

 almost endless extent of flooded country on the banks of the Lower Danube. 

 In all these localities I have watched them for hours or taken their nests. 

 The Black Tern is a late breeder, and it is useless to look for eggs in Denmark 

 before the first week of June, or on the Danube before the last week of May. 

 When a colony of these birds is invaded, their notes are constantly heard ; 

 the most common ones may be represented by the syllables kik and kek, 

 but occasionally a long-drawn kre-e-e is uttered. The nests are built on 

 floating weed, and can very rarely be reached without a boat ; they are 



* The synonymy of the Eastern form is as follows : 

 Sterna surinamensis, Gmel. Syst. Nat. i. p. 604 (1788). 

 Sterna plumbea, Wilson, Am. Orn. vii. p. 83, pi. 60 (1813). 

 Anous plumbea ( Wils.), Steph. Shaw's Gen. Zool. xiii. pt. i. p. 142 (1825). 



Ilydrochelidon surinamensis (Gmel.). I , 



i i, / nr-j \ ( Bonap. Comet. Rend. 1856. p. 773. 

 Ilydrochelidon plumbea ( ll'tls.), | 



Hydrochelidon lariforniis surinamensia (Gmel.), Ridgw. Nom. N. Am. Birds, p. 53 

 (1881). 



