BLACK- HEADED GULL. 313 



birds alighted on the water, and the floating crowd, every bird with its 

 black head to wind, rested on the surface for a few minutes and then rose 

 again in a body. Sometimes a dozen or more perched on the crown of a 

 small birch tree or on the slender twigs of the willows ; then a few 

 hundred bii'ds would suddenly rise from the ground and swoop in a body 

 over the surface of the Avater. Now and then a bird, presumably the owner 

 of one of the nests we had robbed, flew almost close to us, with angry cries; 

 and at any time by waving a hat we could fill the air with thousands of 

 birds, the incessant cries ceasing for a moment as the birds rose, to be 

 instantly resumed when they were fairly on the wing. The note of the 

 Black-headed Gull at its breeding-grounds resembles that of the Common 

 and Arctic Terns. Every modulation of the consonants k and r were pro- 

 duced, such as ki', kr, kr, or kik, kik, kik, varied to kah, kah and kraw, kraw, 

 sometimes kru, km, and often kree-ah, kree-ah. Occasionally the babel of 

 thousands of voices was almost deafening. All the time fresh arrivals 

 were seen coming over the trees from every direction, with steady beat of 

 wing, white tail slightly expanded, and red legs stretched out under it, 

 looking black against the snowy whiteness. Not unfrequently they skim 

 over the tops of the trees with expanded motionless wings. The nests are 

 very slight structures, mere depressions in the spongy ground, which bends 

 beneath the weight of a person walking upon it. Occasionally the eggs 

 are laid on the bare ground, but there is generally a lining of dead grass, 

 sedge, or other weed. 



In a colony of Black- headed Gulls on the island of Zealand, not far 

 from Copenhagen, where the nests were partly placed on an island and 

 partly in the lake, I noticed that those built on the water were large 

 floating structures of reeds and horsetail partly supported by water-plants 

 of various kinds, some of them even standing six or ten inches above the 

 surface of the water, whilst those on the island were very slight, scarcely 

 more than a mere lining to a depression in the grass. In another gullery 

 which I visited on a lagoon on the Pomeranian coast, the nests were built 

 on a floating island, and were large structures, as big as nests of the Coot. 

 The Gulls were breeding in company with Common and Black Terns, and 

 it was remarkable how much shyer they were than those birds. On the 

 Lower Danube the nests were also floating on weeds of various kinds and 

 were large. Although the colony was not a very large one, the birds were 

 demonstrative enough, crying loudly, sometimes a single kak, at others kak, 

 kak, frequently kark, and occasionally kak, kark. The Adriatic Black-headed 

 Gull, which seems to be much more of a sea-bird, has quite a difl'erent note. 



Very few birds are subject to greater variation in the colour of their 

 eggs than the Black-headed Gull. They vary in number from two to three, 

 and four are occasionally found. Sometimes the eggs in one clutch are 

 very much alike; but occasionally one of the eggs is quite diftereut from 



