268 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



even in a cliff swallow's nest. They are very persistent in their at- 

 tempts to raise a family; if a set of eggs is taken the birds will lay a 

 second set of eggs within a very short time and, if necessary, a third set. 



Eggs. — The western bluebird has been known to lay three to eight 

 eggs to a set; probably sets of three are incomplete; sets of four, five, 

 and six seem to be almost equally common; I have heard of only one 

 set of eight, in the collection of Sidney B. Peyton. The eggs are pale 

 blue and practically indistinguishable from those of the eastern blue- 

 bird in every way. The measurements of 50 eggs in the United States 

 National Museum average 20.8 by 16.3 millimeters; the eggs showing 

 the four extremes measure 23.3 by 16.3, 20.1 by 17.5, 19.1 by 16.8, 

 and 20.3»by 15.2 millimeters. 



Young.' — The period of incubation does not seem to have been 

 definitely determined, nor does it seem to be known how long the 

 young remain in the nest; probably both of these periods are similar 

 to those of the eastern bluebird. Incubation of the eggs and brooding 

 of the young seems to be done entirely by the female. Harriet 

 Williams Myers (1912) watched a nest near Los Angeles for 1 hour 

 and 35 minutes. "During this time the female left four times, staying 

 away five minutes once and eight the other times. Her times for 

 brooding were respectively twenty-two, eighteen, ten, and twenty- 

 four minutes. Almost invariably during this and subsequent watch- 

 ings the female did not leave the nest until the male came to it." 

 Four days later, during an hour and a half, "the female left the nest 

 four times as before. The longest interval of staying away was 

 twenty-seven minutes ; the shortest two minutes. The longest interval 

 of brooding was sixteen minutes; the shortest thirteen." Eight days 

 later when there were young in the nest, she watched it for an hour. 

 "During the hour fifteen trips were made to the nest, the feeding 

 being very equally divided. In fact, with two or three exceptions, 

 the birds were both at the nest at once each of the fifteen times." 



James Murdock has sent me a photograph of a western bluebird 

 at its nest in a hole in a yellow-pine log. While he was photographing 

 he noticed that two males and one female were feeding the young; 

 he and his companions saw the two males enter the nest. He writes 

 to me: "One at a time they flew directly in front of us and entered 

 the nest, one coming out while the other went in. Both had food in 

 their bills." 



Kenneth Racey (1939) writes: "The bluebirds are most amusing 

 in the way they keep house and care for the young and they go through 

 the same performance each year. The first brood is brought off and 

 then within a few days the old birds are busy laying and brooding again. 

 When the second brood fledges, both families, usually eight young and 

 the two adults, join in one flock and remain in the neigh bom-hood, 



