284 BULI.ETIN 113, UNITED STATES NATIONAL. MUSEUM. 



in a day. It may be of general interest to note that after the first few days 

 the parent always recognizes and feeds its own young and no other, and, fur- 

 lliermore, the young tern recognizes its own parents and attempts to feed only 

 from tliem. Never but once out of many tliousands of observations did I see a 

 young tern begging food from a stranger. 



Plumages. — I have seen two quite distinct types of downy young. 

 In one the upper parts are variegated with "chamois buff" and 

 black ; in the other the upper parts are deep sooty or brownish bhick, 

 the down on the head and neck being tipped with " ochraceous 

 buff." These colors include the sides of the head, neck, and body, 

 in each case, and the under parts are pure white. Mr. Gitford (1913) 

 describes some downy young, collected on Clipperton Island, as 

 " streaked with grayish brown and dull white on the upper surface, 

 but the white down is tipped with rufous." 



When about 30 days old the young bird is fairly well clothed in 

 its Juvenal plumage. In this plumage the upper parts are "clove 

 brown " ; the back, upper tail-coverts, and wing-coverts are narrowly 

 edged with buff ; the scapulars are broadly tipped with buffy white ; 

 and the under parts are uniform " olive brown," shading off to gray- 

 ish white on the belly and crissum. The bill is small and the tail is 

 square, or nearly so. Probably the light edgings wear away during 

 the winter and apparently a complete prenuptial molt takes place 

 in the spring. I have seen birds in summer, apparently about a 

 year old, with long wings and forked tails, in which the crowns and 

 upper parts are " fuscous black," the foreheads white, and the under 

 parts white, heavily clouded with dusky. At the next molt, the first 

 postnuptial, the adult winter plumage is probably assumed. This 

 differs from the adult nuptial plumage only in having a few scatter- 

 inor white feathers in the crown and the lores. I have not seen suf- 

 ficient material, collected at the proper seasons, to work out the sea- 

 sonal molts of the adult. 



Food. — ^The food of the sooty tern seems to consist almost entirely 

 of small fishes, which it picks up gracefully off the surface of the 

 sea without wetting its plumage. Audubon (1840) says: 



Like some of the smaller gulls, this bird not infrequently hovers close to the 

 water to pick up floating objects, such as small bits of fat pork and greasy sub- 

 stances thrown overboard purposely for maldng the experiment. 



Dr. E. W. Nelson (1899) says of the Pacific variety: 



They feed well out at sea, and were not found anywhere along shore, except 

 when they came to their roosting place on Isabel Island. There were no signs 

 of their roosting about the Tres Marias, although they may roost on some of 

 the outlying rocky islets. Grayson found them in small numbers farther 

 west, about the Revillagigedo Islands. During our trip to the Tres Marias many 

 schools of large fish were encountered swimming close to the surface nnd con- 

 stantly breaking, often with such force and rapidity that the water boiled and 

 foamed over considerable areas. These schools of fish were commonly accom- 



