448 BULLETIN 17 9, UNITED STATES NATIONAL MUSEUM 



darker browns, with sometimes a few underlying spots of pale lilac 

 or drab. Some eggs are evenly covered with fine dots, more often 

 sparingly than thickly, and others show numerous larger spots or 

 small blotches scattered over the egg, or concentrated in a ring 

 about the larger end; rarely an egg is nearly immaculate. The 

 measurements of 50 eggs average 18.8 by 13.5 millimeters; the eggs 

 showing the four extremes measure 21.1 by 13.5, 20.8 by 15.2, 17.3 by 

 13.2, and 19.0 by 12.2 millimeters. 



Young. — Much study has been given to the development, care, 

 and behavior of young barn swallows, and a number of excellent ar- 

 ticles have been published on the subject. Since space will not permit 

 extensive quotations from these, I shall attempt merely a condensed 

 summary of the facts, with a few direct quotations. Readers who 

 would like to make a more detailed study of the subject, are referred 

 to the following more important papers: E. M. Davis (1937), Day- 

 ton Stoner (1935 and 1936a), Wendell P. Smith (1933 and 1937), 

 and Harold B. Wood (1937a and 1937b). 



Most observers give the period of incubation as either 15 or 17 

 days, but some have placed it as low as 13 days; it probably varies 

 some, with 15 a fair average. Both parents share this duty, chang- 

 ing places at frequent intervals, averaging about every 15 minutes. 

 Dr. Wood found that after the third day of incubation they changed 

 at intervals of between 4 and 15 minutes; on the eleventh day the 

 intervals ranged from 6 to 36 minutes. William Brewster (1938) 

 says: "The change which took place on an average of OA'^er every 

 fifteen minutes was effected with singular adroitness. The incoming 

 bird, twittering loudly, flew directly to the nest always aiming for 

 the point where its partner's tail projected over the rim. * * * 

 So quickly was it done that I doubt if a person looking down on the 

 nest from above could have got more than the briefest possible 

 glimpse of the eggs." 



The female apparently incubates during the night, with the male 

 perched near her. Two broods seem to be raised generally in a sea- 

 son in the more temperate portions of the bird's range. Dean Ama- 

 dou observed vhout a dozen pairs nesting in a barn in New York 

 State, and tells me that "almost exactly 60 percent raised a second 

 brood. Usually pairs that used an old nest, constructed in previous 

 years, would raise two broods ; those that built a new one only one." 



The young remain in the nest 18 days (Smith), 19 days (Wood), or 

 23 days (Herrick) and are fed and cared for constantly by both 

 parents. They are not always fed in regular rotation; generally the 

 one that seems most anxious for food is fed first. Probably the 

 youngest birds are fed on regurgitated food, though this does not 

 seem to have been definitely observed; they are, however, known to 

 be fed on fresh insects at an early age, mostly very small insects. 



