E. LÖNNBERG, HYBRID GULLS. 3 



The preserved specimen from ^^/c, 1913 represents a some- 

 what more advanced stage than the figure, because it has 

 already on the upper back some new, slate-coloured feathers. 

 The colour of these is somewhat darker than that of the 

 adult hybrid to be described below. It resembles more 

 nearly the colour of the most anterior feathers of the mantle 

 of a Larus fusciis affinis from Ireland, but there is also an 

 undefined, dusky streak in the middle of each feather. 



The legs of the young hybrid in its second year are 

 reddish pink. The bill is for its greater part about »flesh 

 colour», but somewhat in front of the nostrils it is blackish 

 horn-coloured and with the extreme tip light. It is thus 

 paler than that of a Larus ftiscus of corresponding age. 



The figure of a hybrid from the 15th of March 1915 

 (Pl. 2) shows a still somewhat immature bird. It is in winter 

 plumage, as may be seen from the påle brownisli streaks on 

 the head, hind neck and flanks. The mantle is of a beautiful 

 bluish grey colour. This colour is mucli darker than that of 

 the mantle of L. leucopterus, and even darker than that of 

 L. argentaius, but it is rather similar to that of certain spe- 

 cimens of Larus cachinnayis (especially a specimen in this 

 museum from Lake Kossogol in Mongolia). Scapulars and 

 secondaries display broad white tips, and the primaries are 

 in their outer parts black with white spöts, terminal or sub- 

 terminal. It is the tail, which with its blackish mottling 

 proves the immaturity of the bird. The feet are reddish 

 pink. The greater portion of the bill has a colour which is 

 a little more yellowish than the »pearl grey» of Dauthénay 

 (355, 2). Subterminally it is blackish horn-coloured, and the 

 mandible shows a sign of the beginning red spöt. 



The fourth figure from July 1916 (Pl. 3) shows a bird 

 which, with the exception of some still remaining mottlings 

 on the central tail-feathers, has a fully adult plumage. — 

 The development of birds in confinement is of ten retarded, 

 because even with the best care the conditions are not quite 

 like those of the natural state. This accounts for the dark 

 markings on the tail, which otherwise ought to have disap- 

 peared in a bird of that age. It happens, however, some- 

 times also in nature that such juvenile markings are retained 

 even in breeding birds. This summer for instance I shot 

 for this museum a male Larus fiiscus which belonged to a 



