LIFE HISTOKIES OF NORTH AMERICAN GULLS AND TERNS. 241 



on the pebbly beaches. Often the nests were not over 2 or 3 feet 

 apart and often within that distance of the gulls' nests. 



Eggs. — The eggs of the common tern vary in shape from ovate or 

 short ovate to elongate ovate. The ground color varies from " pale 

 buff " or " olive buff " in the lightest eggs to shades of " wood 

 brown," " cinnamon," or " Isabella color " in the darkest eggs. I 

 have one Q.g^ in my collection which is " pale turquoise green " — a 

 rare type of coloration. There is a great diversity of color patterns 

 in the markings, but most of the eggs are quite heavily spotted with 

 various shades of dark brown and drab, " hair brown," " Vandyke 

 brown," " seal brown," or " clove brown." Some eggs are sparingly 

 spotted and others quite denselj'^ covered with small spots or dots; 

 some are boldly marked with large blotches of dark colors or heavily 

 splashed with lighter shades; many have underlying splashes or 

 blotches of " olive gray " or " lilac gray," producing handsome effects. 

 The measurements of 82 eggs, in the United States National Museum, 

 average 41.5 by 30 millimeters; the eggs showing the four extremes 

 measure 45 by 31.5, 44 by 32.5, 35.5 by 28.5 and 41 by 27.5 milli- 

 meters. 



Young. — I believe that only one brood is normally raised in a 

 season, although it frequently happens that the first set of eggs or 

 young is destroyed, making a second attempt necessary; but Prof. 

 Lynds Jones (1906), who has made a careful study of this species, 

 has produced some evidence to indicate that two broods are often 

 raised. It does not seem to me, however, that his evidence is con- 

 clusive. He has worked out the period of incubation as 21 days 

 and has given a very accurate account of the development of the 

 embryo. I can hardly spare the space to quote from his excellent 

 paper on the subject as freely as it deserves, but the following two 

 passages are well worth repeating: 



Both male and female take regular turns sitting, but my observations indicate 

 that the female spends more time on the nest than the male. In the cases 

 studied, a bird, later found to be the female, approached the nest abruptly and 

 settled upon the eggs without any preliminaries. She remained quiet 40 min- 

 utes, when she uttered a peculiar call, which was repeated at short Intervals, 

 until a bird separated itself from the hovering cloud or company at the water's 

 edge, when she stood up, took a few steps, and flew away. The male alighted 

 on tlie sand several rods to leeward of the nest and approached it gradually, 

 simulated feeding, and called loudly at intervals. When he reached the nest 

 he merely stood over the eggs to protect them from the scorching rays of the 

 sun and kept calling at intervals. In 20 minutes he became more restless, called 

 more frequently, and soon ran some distance to windward of the nest and took 

 wing. Within a few minutes the female alighted on the sand near the nest 

 and went abruptly to it and settled upon the eggs. This maneuver was repeated 

 many times, with slight modifications. 



How do the old birds recognize their own young among the multitude of young 

 birds congregated on the beach? was a question which occupied a good deal of 



