252 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



sand, gravel, or moss or in the rocks. Occasionally a thin lining of 

 dry grasses is used, but an elaborate nest is rarely or never seen. 

 Turner (1886) says: 



The nest is merely a bare spot on the ground. Sometimes a few blades of 

 grass surround tlie margin of the nest, but these seem to be more the result of 

 cleaning off a bare spot than an attempt to construct a nest. 



Palmer (1890), who found this the only species of tern at Funk 

 Island, says that the eggs were laid on the bare rocks, often with 

 broken pieces of granite or pebbles sometimes gathered from a dis- 

 tance arranged about them in a circle. In some cases he found bones 

 of the great auk used in the same manner. Occasionally the eggs 

 were laid in depressions in the gravel, among mussel shells, in crev- 

 ices, amid tangled masses of chickweed 6 inches high that was dead, 

 in a circle 5 inches about ; also in depressions in dead grass as if a 

 mouse's nest had been appropriated. McGregor (1902) says: 



A typical nest was a depression 1 inch deep by 5 inches in diameter, lined 

 with dry grass and weed stalks. 



Parry (1824) says: 



The nest in which the eggs are deposited, and each of which generally con- 

 tained two, consisted merely of a small indentation in the ground, without any 

 downy feathers or other material. 



[Author's note: Eggs. — The Arctic tern raises only one brood 

 in a season and the set usually consists of two eggs ; three eggs are 

 often laid, but larger numbers are very rare. A very large majority, 

 or nearly all, of the sets collected in the far north consist of two eggs. 

 The eggs can not be distinguished from those of the common tern 

 by any constant or even prevailing character, though they seem to 

 average a trifle darker in color and more rounded in shape, which 

 varies from ovate to rounded ovate. The ground color varies 

 greatly ; in the darkest eggs it is " Brussels brown " or " Dresden 

 brown " ; in others it is " Saccardo's olive," " ecru olive," or " dark 

 olive buff " ; and in the lightest egg " water green " or " pale olive 

 buff." The eggs are more or less irregularly spotted or blotched with 

 the darker shades of brown, such as " chaetura black," " bone brown," 

 or " chestnut brown," and often there are underlying spots of vari- 

 ous shades of " brownish drab " or " ecru drab." The measurements 

 of 123 eggs in the United States National Museum average 41 by 

 29.5 millimeters ; the eggs showing the four extremes measure 46 by 

 32 and 37 by 27 millimeters. 



Plumages. — The period of incubation is probably about 21 days. 

 Both sexes incubate. The downy young of the Arctic tern may be 

 distinguished from that of any other American tern by the black or 

 dusky frontal space, which includes the lores and extends across the 

 base of the bill. This dark area matches in color the dark-colored 



