LIFE HISTORIES OP HORTH AMERICAN GULLS AND TEENS. 23 



The period of incubation is 23 days. Both sexes incubate. Mr. 

 A. L. V. Manniehe (1910) writes: 



As far as I could notice the sexes divided the breeding duties evenly between 

 themselves. The posture of the bird while brooding is high, the neck and head 

 erected. While the one bird broods, the other guards its mate and the hunt- 

 ing territory. As soon as a bird of the same species or another larger bird 

 appears upon the scene, the watching bird utters a long penetrating cry and 

 attacks the unwelcome guest; having chased him ofE, the skua again takes 

 its seat near the brooding mate. If you retire some 50 meters the bird will 

 quickly settle upon the nest again. The clamorousness and fearlessness of the 

 bird make it easy to discover nearly every nest, even on a most extensive ter- 

 ritory. 



If the eggs be removed from the nest, the skua will nevertheless as a rule 

 lie down upon the nest for some few minutes. In a certain case I saw a bird 

 lying more than half an hour upon the empty nest. 



■ Young. — The chicks, which soon after the hatching leave the nest, seem 

 during the first days to be principally fed with insects. In the gullet of a newly 

 hatched bird I found a crane-fly (Tipula), but they are even when quite 

 young able to eat lemmings, which the parents hunt, eat, and afterwards dis- 

 gorge before them. The young ones grow very quickly. It is a well-known 

 fact that the young of this skua appear before the first molt in two-color 

 varieties — a pale and a dark. The pale variety seems to occur somewhat more 

 frequently than the dark. 



Though this and the preceding species were both common in north- 

 western Greenland, the members of the Crocker Land Expedition 

 failed to find the nest of either. To illustrate the peculiar behavior 

 of this species near its nest, I quote from Mr. Ekblaw's notes of 

 July 16, 1914, as follows: 



• .Though I failed to find them I felt confident that I had been very near either 

 the eggs or the young of Stercorarius longicaudus to-day. Among the rocks 

 just above Moraine Lake a pair of these birds flew uneasily about me and 

 alighted from time to time near me as I searched at length for the nest that 

 I suspected was on the plateau. ( The male boldly perched, within 40 feet of 

 me, and though the female was shyer she did not leave me far either. An in- 

 genious deceit that the female attempted is worthy of note. After flying 

 nervously near and about me she flew to a large bowlder and settled down 

 snugly beside it, to all appearance as if she were returning to her nest. I 

 hastened to the place exultantly, only to find, when the bird flushed, that she 

 had deceived me. After another nervous flight about me she repeated the 

 performance, and again I was deceived, even though I; waited until I thought 

 she would tire of her strategy, if deceit it were. When she tried a third time 

 to, delude. me I waited to let, her tire, but her patience outwore mine and I 

 finally flushed her. In an hour's search of the moraine afterwards I failed to 

 find any nest. 



Plumages, — The only downy young that I have seen is plainly 

 colored without any dark markings. It varies from "bister" or 

 "buffy brown" above to "wood brown" below, being darkest on 

 the back." Yarrell (1871) describes "a nestling in half-down" as 

 "pale smoke-brown on the downy head and under parts with very 

 dark brown feathers tipped with rufous on the back and wings." 

 174785—21 3 



