60 THE TERNS 



are seldom reached until May. The southward passage lasts from August to 

 October, during which period they are seen not only along the coast, but inland 

 (cf. O. V. Aplin, Birds of Oxfordshire, p. 166). Few remain till October, and some 

 have reached the Spanish and Portuguese coasts by September (see below). 

 The species is scheduled in the B. 0, C. Migration Reports, but very little definite 

 information has as yet been collected. As regards habits, the species is said to 

 appear at its summer haunts in the morning, having arrived during the night, the 

 numbers increasing nightly for ten or twelve nights (Migration Report, 1883, p. 45). 

 Several interesting records of marked common-terns recovered, exist : (1) marked 

 at Ravenglass, Cumberland, July 30, 1909, recovered at Espina, Galicia, Spain, 

 September 21, 1909 ; (2) marked at Ravenglass July 23, 1910, recovered 

 25 miles south of Oporto, Portugal, about September 12, 1910 ; (3) marked at the 

 Hook of Holland July 16, 1910, recovered at Boulogne, France, September 1, 1910 

 (cf. Witherby, British Birds, iii. p. 219, and iv. p. 179). [A. L. T.] 



4. Nest and Eggs. The nesting-sites vary extraordinarily : off the west 

 of Scotland one may find large colonies breeding on the bare, water-worn rocks ; 

 in East Anglia and other parts the eggs are laid on the great shingle-beds close to the 

 sea ; in Holland the nests are sometimes on short meadow grass or in sandy mud- 

 flats in the polders, and at other times floating on the surface of fresh-water meers 

 inland. In some cases there is no lining whatever, a natural cavity in rock being 

 used or a hollow in sand : at other times dry bents, bits of dead reed, and other 

 vegetable matter are carelessly arranged. (PI. xuu.) The eggs are 2 to 3 in 

 number, generally the latter ; but I have several times seen 4 or 5 together, pro- 

 bably laid by more than one bird. The ground-colour varies from dull greyish to 

 ochreous and brownish, blotched and spotted, sometimes boldly and richly, but 

 more often rather sparingly with dark blackish brown and underlying ashy grey. 

 Some eggs when first laid have a very beautiful blue ground, which unfortunately 

 soon fades, and a distinctly red variety also occurs on rare occasions. (PI. H.) 

 Average size of 108 eggs, 1-61 x 1-19 in. [40' x 30'2 mm.]. Incubation commences 

 as soon as the first egg is laid, and apparently lasts 20-21 days from the date of 

 the full clutch. This is confirmed by W. Evans's observations on eggs hatched 

 in incubators, which hatched on the twenty-second and twenty-third days. 

 Naumann states that both sexes incubate, but chiefly the hen, who also broods 

 during the night. In fine sunny weather the eggs are left uncovered for long 

 periods. Saunders states that exceptionally eggs have been found by May 15; 

 but this is very unusual, and as a rule they are laid about the beginning of June, 



