LIFE HISTORIES OF NORTH AMERICAN GUULS AND TERNS. 267 



I believe that the series of eggs collected by Mr. Hersey are the only 

 authentic eggs of the Aleutian tern in existence outside of those col- 

 lected for the United States National Museum referred to above. 

 These eggs vary in shape from ovate to elongate ovate, with a de- 

 cided tendency toward the latter. The shell is thin, with very little 

 luster. The ground color varies from " clay color " or " honey 

 yellow " to " olive buff " or " Marguerite yellow." In a general way, 

 they are not only more elongated, but darker and more richly colored 

 than other tern's eggs. They are usually heavily marked with large 

 blotches and smaller spots, scattered irregularly over the egg or 

 coalesced into longitudinal splashes or in a wreath near the larger 

 end. These markings consist of underlying spots or splashes of 

 various shades of drab, from " deep brownish drab " to " pallid 

 brownish drab," overlaid with bold and handsome blotches and spots 

 of the darker and richer shades of brown, such as "Mars brown," 

 " Vandyke brown," and " light seal brown." The measurements of 

 44 eggs, in the United States National Museum and the writer's col- 

 lections, average 42 by 29 millimeters; the eggs showing the four 

 extremes measure 46.7 by 30, 45 by 30.5, and 40 by 27.5 milli- 

 meters. 



Young. — Only one brood is raised in a season, and, according to 

 Mr. Hersey's experience, no second attempt to raise a brood is made 

 if the first eggs are taken. Mr. Turner (1886) gives the period of 

 incubation as 17 days, but this is evidently an error, as the common 

 and roseate terns are known to have an incubation period of 21 daj^s. 

 Doctor Nelson (1887) says: 



The eggs are rarely laid before June 5 or 10, and I found one egg with an 

 embryo two-third grown on September 1, but this is very unusual. The young 

 of aleutica are hatched from the last of June until September, and the first ones 

 are on the wing by the last of July. 



Speaking of the second island, referred to above, near St. Michael, 

 he writes: 



On September 1, 1879, I visited the island near Kegikhtowik and found from 

 GO to 80 adults of this species haunting the vicinity and circling in gi-aceful 

 flight all about the island. When we landed and passed over the island the 

 birds showed considerable anxiety and continually uttered a thin, clear, thrilling 

 whistle. With the exception of some broken eggshells and the old depressions 

 showing the nesting sites, nothing but a single egg was found there ; but as we 

 walked out on a low cape, covered with large scattered rocks, we put up, one 

 after the other, a considerable number of young birds just able to fly, and a 

 goodly number were secured. When they arose they had a queer, erratic, dazed 

 kind of flight, reminding me of the flight of an owl suddenly disturbed in the 

 daytime. The old birds kept flying in toward the point with small fishes in 

 their beaks, but although we concealed ourselves in the rocks others of the 

 party evidently warned them, so that only two or three of the adults were 

 taken. One young bird was fired at and missed and flew wildly out to sea, 

 when it was joined by an old bird, which kept close to It, and as the young bird 



