16 BULLETIN- 113, UNITED STATES NATIONAL MUSEUM. 



neck clouded with light drab and the dark crown less pronounced 

 than in spring. This disappears partially by wear, but I have seen 

 one adult, taken in California on April 29, in which this plumage 

 was being replaced by a partial molt. 



Adult parasitic jaegers can be distinguished in life at a long dis- 

 tance by the downward extension of the drab mantle on the sides of 

 the neck which seems to form a partial collar ; this is entirely absent 

 in the long-tailed jaeger; the long central tail feathers are more 

 pointed and are held differently in flight from those of the pomarine 

 jaeger, as explained under that species; these feathers are, however, 

 an unsafe guide by which to distinguish the parasitic and long-tailed 

 jaegers, as there is much individual variation and overlapping. 

 These last two species can hardly be distinguished in life in the im- 

 mature plumages. For the best characters by which they can be 

 distinguished in the hand I would refer the reader to Dr. Leonhard 

 Stejneger's (1885) excellent remarks on the subject. 



In the dark phase, which may prove to be a distinct species, the 

 sequence of molts and plumages is practically the same as outlined 

 above, though the birds are much darker in all stages. During the 

 first year the brown edgings are conspicuous, but during the second 

 they are replaced by narrower and whiter edgings, the under tail- 

 coverts being heavily barred in both cases. The adult plumage is 

 wholly sooty, with sometimes a trace of the golden collar.] 



The proportions of the two phases vary considerably. At Ips- 

 wich in the migrations, which extend over most of the summer, the 

 birds in light phase outnumber the dark birds in the proportion of 

 8 or 10 to 1. On the Labrador coast I found those in the dark phase 

 more numerous in proportion than at Ipswich. Richardson (1825) 

 says that on the banks of the Coppermine River in the beginning of 

 July the greater part of them had dark abdomens. Grinnell (1900) 

 in Alaska found a sooty bird mated with a light one and remarks 

 that " one could scarcely believe them to be of the same species." He 

 says that half of this species in June and July were in the dark 

 plumage. Thayer and Bangs (1914) mention two pairs in northern 

 Siberia, where all four birds were in the light phase, and one pair 

 at Kodiak Island, Alaska, where the birds were in the dark phase. 

 Nelson (1887) mentioned a similar dark couple. The difference be- 

 tween the two phases seems as great as that between the greater and 

 the sooty shearwaters. 



Food. — The feeding habits of the parasitic jaeger vary consider- 

 ably with the locality. The host on which it preys is in some places, 

 as on the New England coast, the common tern, although the arctic, 

 roseate, and least terns, as well as the Bonaparte's gull, maj^ in places 

 be added. On the eastern Labrador coast I found the ffreat flocks of 



