E. LÖNNBERG, HYBRID GULLS. 17 



The pattern especially of the first and second primaries 

 of these Gulls closely resembles the corresponding one of 

 Larus marinus, although it contains less black, and it is thus 

 clearly an inheritance from that parental side. It is also of 

 interest to find that the pattern of the third and fourth 

 primaries of the hybrids nearly resemble the pattern of the 

 fourth and fifth primaries of L. marinus resp. The general 

 reduction of the black pigment in the hybrid explains the 

 fact that its third priraary resembles the fourth, and not the 

 third, primary of L. marinus, and so on. The third, fourth 

 and fifth primaries of L. marinus are namely essentially of 

 the same type with a white tip, and a white spöt on the 

 inner web at some distance from the tip, and these two white 

 markings are separated by black, which reaches further proxi- 

 mally on the outer than on the inner web. This black is 

 gradually reduced in its proximal portion from the third to 

 the fifth. The third primary of the hybrid has thus had the 

 faculty of developing black pigment to approximately the 

 same (reduced) amount as the fourth primary of L. marinus, 

 and the fourth primary of the former about as much as the 

 fifth (or sixth) of the latter. 



With regard to their dimensions these hybrids are strong 

 and powerful birds. The specimen from Upernivik has a 

 length of wing amounting to 485 mm, or a little more, and 

 the adult one from the Zool. Garden of Copenhagen is slightly 

 larger with the length of the wing 490 mm. The culmen of 

 the former is about 66 mm and of the latter perhaps 1 mm 

 more. 



From the descriptive notes above it will appear that the 

 young hybrids of this origin in their juvenile plumages are 

 more similar to young Larus marinus than to L. glaucus of 

 similar age, and this stånds as an analogy to that which has 

 been stated above concerning the young Larus fuscus X L. 

 leucopterus hybrids, which are more similar to young L. fuscus 

 than to young L. leucopterus. With other words both these 

 combi nations of hybrids resemble in their youth the corre- 

 sponding stages of the young of the darker, or more pigmented 

 parental species. This depends, of course, on an inherited 

 faculty of producing more pigment than the young of the 

 respective lighter parental species is able to. On the other 

 hand there is no doubt that tlie påle young of Larus glaucus, 



Arkiv för zoologi. Bd 12. N:o 7. 2 



