LIFE HISTORIES OF NORTH AMERICAN GULLS AND TERNS. 135 



Mr. George (Jr. Cantwell has sent me a photograph of a remarkable 

 nest of a ring-billed gull which he found at Prince William Sound, 

 Alaska, in June, 1912. His notes state that the nest was " made of 

 usual material, but unique in the matter of situation, placed in the 

 crown of a dwarf spruce, that grew to the height of about 4 feet 

 above the surface of a small rock, upon which it had taken root. 

 The rock set in an open bay of the salt water, about one-half a mile 

 from shore. On other near-by islands a colony of Arctic terns were 

 nesting, and on the bars of a stream on the near-by mainland other 

 ring-billed gulls had nests. This was the only nest noted in the 

 trees there, or on any other occasion." 



Eggs. — The ring-billed gull normally raises but one brood, and the 

 fidl set usually consists of three eggs; often only two eggs are laid, 

 and sets of four are very rare. The eggs are subject to the usual varia- 

 tions in gulls' eggs. In shape they are usually ovate or short ovate ; 

 the shell is smooth, thin, and almost lusterless. The ground color 

 varies from " Brussel's brown " or " snuff brown " to " pinkish buff " 

 or " cartridge buff " in the commoner types of eggs ; in the greener 

 types of eggs, which are rarer, the ground color varies from " deep 

 olive buff " to " pale oliA'e buff," or in some cases to " yellowish glau- 

 cous," which makes the egg look much greener than it really is. The 

 prevailing types of eggs show the usual markings of gulls' eggs — 

 spots and blotches of various sizes and shapes irregularly distributed ; 

 some eggs are finely speclded all over; in some the markings are 

 confluent into a ring; and some are handsomely decorated with ir- 

 regular scrawls, splashes, or blotches. Nearly all eggs show under- 

 lying spots or blotches of various shades of " quaker drab," lavender 

 or " mouse gray." These markings are very faint in the lighter types. 

 The heavier and darker markings are made up of various shades of 

 brown, often several shades on the same ^gg overlapping each other 

 as if superimposed; these vary from " blackish brown" or " fuscous 

 black " to " burnt umber," " russet," or " Dresden brown." Often the 

 darkest markings are on the lightest colored eggs, making strong 

 contrasts. The measurements of 40 eggs in the United States Na- 

 tional Museum and the author's collections average 59.3 by 42.3 milli- 

 meters; the eggs showing the four extremes measure 64.5 by 42.5, 

 59.5 by 44.5, 54 by 40.5, and 60.5 by 40 millimeters. 



Young. — The period of incubation is about 21 days. The young 

 remain in the nest for a few days, but soon learn to run about and 

 hide among the rocks or under the vegetation near their nests. They 

 learn to swim at an early age, and may often be seen swimming out 

 from the shores of their island home when disturbed. They are care- 

 fully guarded by their anxious parents and driven back to dry land 

 as soon as the dangerous intruder has departed. They seem to ap- 

 preciate the value of their protective coloring, and will remain hid- 

 174785—21 10 



