224 BTILLETIN" 113, TTNTTED STATES NATIONAL MUSEUM. 



the slightest concern each tern sought its own egg despite the fact that it 

 had been moved several feet and placed in a different nest. After allowing each 

 bird to remain on its egg for 15 minutes, I again left the blind and retrans- 

 ferred the eggs with the same result as before. Each parent bird settled on 

 its own egg without hesitation, and, as before, not evidencing any surprise over 

 the change of the location. 



The eggs of Cabot's tern are certainly beautiful and subject to 

 great variation; they make one of the prettiest series in the egg 

 collector's cabinet. The ground color on the prettiest eggs varies 

 from "seashell pink " to " pale cinnamon pink," or from " pale pink- 

 ish buff" to "pale ochraceous buff." Some show various olive 

 shades, from ^ olive buff " to " light buff ; " others vary from creamy 

 white to pure dull white. The markings vary endlessly in size, 

 shape, and extent. Some eggs are uniformly covered with small 

 spots, densely or sparingly; others are boldly marked with large 

 heavy blotches or irregular, fantastic scrawls. These markings may 

 be confluent in a ring at either end. The markings are usually 

 in the darkest shades of " blackish brown " or black ; occasionally 

 they are more or less washed out on the edges, as in the royal tern's 

 eggs; occasionally blotches or scrawls of " burnt umber " or " russet " 

 are overlaid with darker shades; spots, blotches, and scrawls of 

 " pale lavender gray " are seen under the bolder markings. Often 

 both fine spots and bold scrawls are seen on the same egg. When 

 these include two shades of brown and the lavender gray on a pink 

 background the effect is beautiful. One odd egg in my collection 

 has the pink ground color nearly concealed by fine scrawls of several 

 shades of reddish brown, suggesting certain types of falcon's eggs. 

 The shell is smooth, but without luster. The shape varies from 

 ovate to elongate ovate. The measurements of 41 eggs, in the United 

 States National Museum and the writer's collections, average 51.1 

 by 36 millimeters; the eggs showing the four extremes measure 

 57 by 37.5, 51.5 by 38.5 and 46 by 33 millimeters. 



Town^.— Incubation seems to be shared by both sexes and lasts 

 for about three weeks. Morris (1903) quotes Selby as saying: 



As soon as the young birds become tolerably fledged, but before they are 

 altogether able to fly, they frequently take to the water, swimming off to the 

 smaller rocks, where they continue to be fed by the parents until capable 

 of joining them in their fishing excursions. 



Plumages. — Downy young Cabot's terns do not show so much 

 variation as young royal terns and will average much lighter in 

 color. They are seldom much darker than " cartridge buff " on the 

 upper parts and are usually buffy white or white. They are also 

 usually immaculate; often a few small dusky tips are seen on the 

 down of the back, and occasionally an individual is uniformly mot- 



