334 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



Aleutians, Dr. Stejneger (1885) says: "They are not known to breed 

 on the islands, where they have been collected only during the spring 

 migration. In 1882 I shot only one specimen on each island, but 

 during the 'bird-wave' of 1883, they were plentiful in the northern 

 part of Bering Island. The birds occurring on the islands belong to 

 the same stock as those inhabiting the mainland of Kamtschatka." 



Courtship. — All the small Old World leaf -warblers have more or less 

 well-defined postures and display actions in courtship, but those of 

 Acanthopneuste borealis have yet to be adequately observed. Dixon 

 records two birds that were "seen to perch on a limb fluttering their 

 wings quite audibly and uttering a harsh 'chit' at frequent intervals," 

 which sounds like a display action, though it might possibly have been 

 aggressive, and I have observed what was evidently a sexual chase of 

 the type met with in so many small birds, among the bushes in a 

 Norwegian birch swamp late in June. 



Nesting. — The nest is placed among vegetation on the ground and 

 is a domed structure with entrance hole at the side, built of fine 

 grasses with commonly some moss and dead leaves and lined with fine 

 grass. It is characteristic that feathers are absent from the lining, 

 though one recent author has recorded three small ones in one nest. 



Collett (1886) found three nests near Matsjok, of which he says: 



The first nest I found (on July 27th) was placed at the foot of a slope thickly 

 covered with birch trees, and was well hidden by Cornus suecica, halfgrown 

 Chamaenerion angustifolium, Veronica longifolia, and Melica nutans. It lay 

 under the root of a tree, which partly formed a roof to the nest. The other nest, 

 found the same day at another slope in the wood, had no such protection; but 

 both nests were completely domed, as is usual in those of the other Phylloscopi. 

 They were most loosely constructed; the outer base was composed of some dry 

 birch-leaves; the outside consisted of coarse straws and moss, the interior of finer 

 straws, but without a trace of hairs or feathers. The number of young birds in 

 the first was seven, in the other six. Each brood was about nine days old. 



The third nest (July 28th) also lay on a high slope covered with birch trees, 

 protected by a thin branch of juniper and surrounded mostly by Cornus suecica, 

 while the other tall forest plants here were absent. This nest was thus some- 

 what exposed. Like the others, it was domed and loosely put together, inside 

 with fine straws, outside of larger, but nevertheless soft, straws, as well as a good 

 deal of two kinds of moss which covered the ground in the immediate neighbour- 

 hood, viz. Hylocomium splendens, Hedw., and Dicranum scoparium, Hedw. The 

 number of young was six, nearly ready to fly. 



Henry Seebohm (1879) writes of its nesting in Siberia: "When I 

 left the Arctic circle it had probably not commenced to breed; but 

 on the 6th of July I had the good fortune to shoot a bird from its nest 

 at Egaska, in latitude 67°. * * * The nest was built on the 

 ground in a wood thinly scattered with trees, and was placed in a 

 recess on the side of a tussock or little mound of grass and other 

 plants. It was semidomed, the outside being composed of moss, and 



