THE BLACKHEADED-GULL 137 



of fresh pigment into the feathers. 1 As long ago, however, as 1866, 

 Mr. H. Blake Knox pointed out in the Zoologist 2 that the change is 

 by moult, and that the new brown feathers sprout up from under the 

 white and displace them. He limited the spring moult to the head. 

 Dr. P. H. Bahr has since shown that it extends to the breast and 

 back as well. 3 



Soon after it assumes the brown hood, the blackhead moves 

 towards its summer quarters. Before actually settling on the nesting- 

 ground, it appears to frequent the fields in the neighbourhood for 

 three or more weeks. At Scoulton, in Norfolk, where the birds are 

 "preserved" for the sake of their eggs, and are therefore carefully 

 watched, I was told that the first arrivals do not alight on the 

 nesting-ground till March 17th-20th, but they are seen in numbers 

 in the surrounding country as early as mid-February. Their habits 

 at this period have yet to be closely studied, and should prove full 

 of interest, for it is then, no doubt, that they pair off for the 

 season. 



The breeding-places, for the most part, may be classed under 

 one or other of two types. The first may be called the marsh or lake 

 colony. That at Scoulton is an example. Here the nests are built 

 on swampy ground, from which the reeds have been cut, at one 

 end of the large island in the lake. Elsewhere they are built among 

 the water-plants growing on the margin of lakes, and also on tussocks 

 rising from lake or swamp. In the Danube delta Mr. Jourdain found 

 nests floating on water five feet deep, with no support except that 

 occasionally provided by a water-lily leaf or stalk. These colonies are 

 found both inland, and, as at Dungeness, near the sea. They form a 

 remarkable contrast to the second and less usual type, of which 

 Ravenglass and Walney are good examples. At these two places 

 the birds nest in thousands, chiefly on the ridges and sides of arid, 

 sun-scorched sandhills above the beach, sometimes hundreds of yards 



1 Yarrell, History of British Birds, iii. 603. 2 1866, p. 361. 



3 British Birds (periodical), iii. 105, where a careful and detailed account of the spring moult 

 is given and illustrated. 



VOL. III. S 



