49 



FAMILY STERCORARIID2E. SKUAS AND JAEGERS. 



General Description. The Jaegers are predaceoua sea-birds. In colour they are dark 

 brown and white. The family shows a peculiar dichromatism and all Canadian species 

 occur in two colour phases, one an almost evenly dark brown and the other a dark or slaty 

 brown with white or light head, neck, and underparts and an almost black cap. 



Distinctions. The bills of the Jaegers (See Figure 3, p. 18) are characteristic, there 

 being a distinct nail at the tip forming a well-marked hook plainly separable from the 

 remaining cere at the base of the bill. This character separates them easily from the 

 Gulls, whereas the presence of nostrils and two instead of three toe webs (Figure 6, p. 19 

 for comparison), distinguishes them from the Cormorants which have bills similar in out- 

 line. The fact that the nostrils are not in tubes (Figure 11, p. 19) differentiates them from 

 the Petrels which they otherwise resemble. 



Field Marks. Jaegers are dark in colour above, have a quite conspicuous light band 

 across the underside of the wing near the tip, and are hawk-like in flight. Two of the 

 three species, in the adult state, show elongated tail feathers that are good recognition 

 marks. 



Nesting. On the ground, in grass. 



The occurrence of the two colour phases as well as every possible 

 intermediate plumage, makes the identification of some of the Jaegers a 

 difficult matter. Jaegers are pirates of the air; they pursue successful 

 fishing birds and force them to disgorge the fish they have swallowed; 

 and eggs and young birds in the nest are never safe from them. 



Three Jaegers occur in eastern Canada and one Skua the latter too 

 rare and accidental, except off the outer Newfoundland coast, for further 

 mention. 



Economic Status. The Jaegers are not very numerous and except in 

 far away, wild localities, where numbers give them local importance, they 

 are of little economic influence. 



Genus Stercorarius. Jaegers. 



36. Pomarine Jaeger. BO'SN. (BOATSWAIN). FR. LE LABBE POMARIN. Stercorarius 

 pomarinus. L, 22. (Tail 9 -25, projections of centre feathers beyond outer ones 4-25.) 

 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 probably the best 

 field marks. 



Nesting. On the 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. FR. 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 having 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. This distinction, however, is not infallible and occasional 

 specimens occur that are very difficult of determination. 



