49 



This is the largest of the Jaegers. It resembles the other two species in coloration so 

 closely that its separation is difficult except by size and in adult condition. The species 

 occurs in two colour phases and in all intermediate stages. 



Distinctions. Elongated middle tail feathers of adult are wide and twisted at the 

 tip so as to lie in a vertical instead of a horizontal plane. 



Field Marks. The broad, elongated, twisted tail feathers are propably the best 

 field marks. 



Nesting. On ground, in grass. 



Distribution. Breeds on the islands and mainland in the Arctic across the continent. 

 Occurs on the sea coasts farther south, only as a migrant. 



37. Parasitic Jaeger. PR. LE LABBE PARASITE. Stercorarius parasiticus. L, 17' 

 (Tail 8-25, projection of middle feathers beyond outer ones 3-25.) This species occurs 

 in two colour phases, a light, and a dark one. In the dark phase the general colour 

 is dark brown slightly lighter below and with a black cap. In the light phase the under- 

 parts, breast, neck, and face are white, with black cap. Intermediate stages of coloration 

 also occur. 



Distinctions. The smaller size of this bird should distinguish it from the preceding 

 in all plumages. In the adult, the middle tail feathers project only 3 inches beyond the 

 others instead of 7 inches as in the next species and are slender instead of broad and twisted 

 as in the last species. Immature birds of the Long-tailed species, not haying the long 

 tail feathers, are almost exactly similar to this species, and can best be distinguished by 

 the colour of the shafts of the primary feathers. In the Parasitic, the shafts of the three 

 first feathers are white and the remainder are progressively darker as they succeed each 

 other on the wing. In the Long-tailed, there is an abrupt darkening of colour of the shafts 

 after the third primary. 



Field Marks. Small projection of the middle tail feathers as above and their not 

 being twisted make a field mark of fair reliability in adult birds. 



Nesting. On ground, on the moors and tundras of the north. 



Distribution. Breeds in the Arctic across the continent and is much more common 

 on the seaboard in migration than inland, where it is a very rare though possibly a regular 

 straggler. 



This is the only Jaeger that is likely to be met with in the interior on 

 the Great Lakes. Other species have been recorded, but upon investigation, 

 except in one instance, they have been found to be young birds incorrectly 

 identified, usually on the ground of their lack of elongated tail. 



38. Long-tailed Jaeger. FR. LE LABBE A LONGUE QUEUE. Stercorarius 

 caudus. L, 21. (Tail 13-25, projection of centre feather beyond outer ones 8.) Very 

 similar in coloration to the preceding, but the long slender middle tail feathers project 7 

 or 8 inches beyond the others instead of only 3. 



Distinctions. The Long-tailed Jaeger although having nearly the measurements 

 of the Pomarine, owing to the great tail length being included, is a much smaller bird 

 than either of the other two species. Size should distinguish it. Juveniles are often con- 

 fused with the Parasitic but the wing characters given under that species are diagnostic. 



Field Marks. It is possible to separate only adult Jaegers in life; the long middle 

 tail feathers being the best guide. 



Nesting. Similar to that of the other Jaegers. 



Distribution. Breeds in the Arctics of Europe, Asia, and America. Is only of rare 

 occurrence on east coast. 



Though the Long-tailed Jaeger has been recorded on the Great Lakes 

 most of such occurrences are misidentifications of juveniles of the preceding 

 species. 



FAMILY LARID^E. GULLS AND TERNS. 



General Description. The Gulls and Terns are long-winged swimmers, easily separable 

 from the Jaegers by the shape and construction of the bill which shows a single continuous 

 surface without distinct parts or joints (Figures 4, 5, p. 18). The colours of the adult 

 are usually pure white, with white, pearl-grey, or black mantles, often with black wing 

 tips, hood, cape, or cheek spots. , 



