LIFE HISTORIES OF 2T0RTH AMERICAN GULLS AND TERNS. 259 



in the sand, on bare ground, or on rocks without any attempt at con- 

 cealment or at nest building. 



Eggs. — Some observers suggest that the roseate and common terns 

 raise two broods in a season; fresh eggs are often found late in 

 August, but these are probably laid by birds that have failed to raise 

 their first broods. The usual set consists of two eggs; three are fre- 

 quently found in a nest and rarely four. The larger sets often, 

 though not always, show evidence of having been deposited by more 

 than one bird. 



The eggs of the roseate tern are similar to, and often indistin- 

 guishable from, those of the other small terns ; but when a large series 

 is compared with others the average difference is well marked. 

 They will average a trifle longer and the markings are smaller 

 and more evenly distributed, with fewer of the large bold mark- 

 ings when compared with a series of eggs of the common tern. 

 There is less variation in the ground color, which ranges from 

 " cream buff " to " cartridge buff " or " pale olive buff." The darker 

 and richer colors of other terns' eggs are seldom, if ever, seen in this 

 species. A majority of the eggs are evenly sprinlded with small spots 

 or dots over the entire surface, either with or without an occasional 

 larger spot ; these spots are seldom large enough to be called blotches 

 and never as large and conspicuous as they are on the eggs of the 

 common tern. These markings are in the darker shades of brown 

 from " warm sepia " to " dark clove brown." There are often numer- 

 ous spots of various shades of violet, plumbeous or lavender gray, 

 underlying the darker markings. In shape the eggs vary from 

 ovate to elongate ovate, usually quite pointed. The shell is 

 smooth, thin, and without luster. The measurements of 87 eggs, 

 in the United States National Museum, average 42 by 30 milli- 

 meters; the eggs showing the four extremes measure 45.5 by 31, 43.5 

 by 32, 38 by 30, and 44 by 27.5 millimeters. 



The exact period of incubation was found to be 21 days by Prof. 

 Lynds Jones (1906), who has also given us (1903) a good account of 

 the process, as follows : 



In two cases that were under careful observation for some time both parents 

 performed the office of incubation in regular turn. The one that I judged to 

 be the female brooded the eggs, tucking them carefully under her feathers, 

 but the male merely stood above them, apparently shielding them from the 

 burning sun, vphile the female went for a lunch and bath. The incoming bird 

 uttered a peculiar rattling sound just before alighting some 20 feet from the 

 nest, when the brooding bird got up and immediately flew away. The relief 

 carelessly sauntered toward the nest, made believe picking up food wlien it 

 reached the nest, then stood over it a moment before settling down, if tlie fe- 

 male. Neither bird remained on the nest over an hour; the male usually less 

 than 40 minutes, not waiting for the female to appear every time before leaving. 



