40 BRITAIN^S BIRDS AND THEIR NESTS. 



birds. The migrations of the species under discussion 

 were first studied in this way in Germany. The little 

 fishing village of Rossitten, at the south-eastern corner of 

 the Baltic Sea, is the seat of the German Ornithological 

 Society's Vogehvarte, or ornithological station, while near 

 the village there happens to be a colony of Black-headed 

 Gulls. For several years the young birds of this colony 

 have been marked with light aluminium foot-rings in- 

 scribed with the address ' Vogelwarte, Rossitten,' in 

 addition to a number, different in each case. Some fifty 

 of these have been heard of again, and the results so far 

 are of great interest. Some of the birds had followed 

 the north coast of Germany and the north and west 

 coasts of France, some touching the south of England ; 

 others had gone so far, and then cut across Europe, 

 perhaps following the Rhine and Rhone, and had reached 

 the Balearic Islands ; still others had crossed at once to 

 the Adriatic and had reached the south of Italy, and 

 even Tunis. In the same way Black-headed Gulls in 

 this country are now being marked with rings inscribed 

 with various addresses, and in a few years we shall 

 probably know much more than we do now of the life- 

 history of the members of this interesting and familiar 

 species nesting in the British Isles. 



By the middle of Febiniary or early in March most of 

 the Gulls have returned from their wanderings and have 

 assembled at their nesting haunts. The nests are large 

 bundles of herbage, quite sufficient to keep the eggs high 

 and dry above the water or mud. Late in April or early 

 in May the eggs are laid. They are frequently two, but 

 more often three in number. Genuine clutches of four 

 eggs are probably not very rare ; but fom- or more eggs 

 in the same nest are probably to be regarded as the joint 

 product of two hens. In colour the eggs are very variable. 



