216 
CHARADRII FORMES 
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. Skuas and jaegers are pirates of the air; they pursue 
successful fishing birds and force them to drop the fish they have caught. 
Eggs and young birds in the nest are never safe from them. 
Three jaegers occur in Canada and two skuas — the latter very rare. 
Economic Status. The jaegers are not very numerous and except in 
far away, wild localities, where numbers give them local importance, they 
have no economic influence. 
36. Pomarine Jaeger, bos’n (boatswain) bird, le labbe pomarin. Stercor- 
arius pomarinus. L, 22 (tail 9-25 maximum). Projection of centre tail feathers beyond 
outer ones 4 -25 inches. Occurs in two phases and intermediate stages. In the dark phase, 
the general colour is dark brown, slightly lighter below and on cheeks, with a black cap. 
In light phase, the underparts, breast, neck, and face are white; cheeks mostly, and throat 
in some cases, tinged with golden; the cap is black (Figure 311) and the rest of body dark 
brown. Dark barring may occur on flanks, breast, and underparts. Hardly distinguish- 
able by colour from the two next jaegers. 
Distinctions. The largest of the three jaegers. (Disregarding the long projecting 
tail feathers, 17-75 in length.) A jaeger with a wing over 13| inches probably belongs to 
this species. The elongated tail feathers of the 
adult are wide, instead of pointed, and twisted 
at the tip so that the ends stand in a vertical 
plane instead of lying horizontally (Figure 313;. 
Field Marks. For recognition as a jaeger 
see Field Marks under Family, page 215. The 
trailing, broad, twisted tail feathers are prob- 
ably the best specific field marks. 
Nesting. On the ground, on the moors 
and tundras of the north. 
Distribution.. Breeds on the islands and mainland of the Arctic, across the continent. 
Recorded from Great Slave and Athabaska Lakes, but not elsewhere in the interior, except 
one record from Saskatchewan and one from Ontario. Much less common on the British 
Columbian than on the east coast. 
37. Parasitic Jaeger, arctic or Richardson's skua, le labbe parasite. Ster- 
corarius parasiticus. L, 17 (tail 8*25 maximum). (Projection of centre tail feathers 3-25. 
In coloration hardly distinguishable from the other two 
jaegers (Sec preceding species for general description). 
Occurs in both phases there described and in various inter- 
mediate stages. 
Distinctions. Decidedly smaller than the Pomarine, 
slightly larger than Long-tailed Jaegers. Length, dis- 
regarding elongated tail feathers, 13-75 instead of the 
17-75 of the former or 13 of the latter. A jaeger with a 
wing under 13 inches is probably either this or the next 
species. The elongated tail feathers of the adult are 
pointed and narrow instead of wide and twisted as in the 
Pomarine and only 3-25 inches projection beyond the 
rest, instead of 8 inches as in the Long-tailed (Compare 
Figure 314 with 313 and 315). Immatures and birds with 
the centre tail feathers in moult are difficult to separate from the Long-tailed. The l>est 
distinction seems to be in the colour of the shafts of the primary feathers. In this species 
the shafts of the three first primaries (counting from outside) are white, the remainder 
darkening progressively as they succeed each other on the wing. In the Long-tailed there 
is an abrupt darkening of colour of the shafts with the third primary. This distinction 
is not infallible and occasional juvenile specimens are very difficult of determination. 
Field Marks. For recognition marks as a jaeger See Family Field Marks, page 215. 
The small projection of middle tail feathers and their not being broad and twisted probably 
make the best specific field marks. 
Nesting. On the ground, on the moors and tundras of the north. 
Figure 314 
Tail of Parasitic Jaeger; 
scale, about 
Tail of Pomarine Jaeger; scale, about 1. 
