BLUE-GRAY GNATCATCHER 351 



eggs average 14.5 by 11.2 millimeters; the eggs showing the four 

 extremes measure 15.5 by 11.2, 15.2 by 14.7, 13.2 by 11.2, and 15.2 

 by 10.7 millimeters.] 



Young. — Little has been written about the nest life of the blue- 

 gray gnatcatcher, and my own notes are peculiarly deficient in this 

 respect. Out of the many gnatcatcher nests that I have seen, I 

 find that I have not followed the history of a single one completely 

 through any one phase of its development. 



Incubation is said to require about thirteen days from the laying 

 of the last egg. G. A. Petrides (MS.), writing of a nest near Wash- 

 ington, D. C, found "day-old young" on May 21 in a nest where 

 the last egg of the set had been laid on May 8. William Palmer 

 (1906) stated that, during incubation, the female parent "rarely 

 leaves the nest" and is fed there by the male, the inference being 

 that he does not share in the duties of incubation. On the other 

 hand, Mrs. Nice (1932) remarked the close cooperation between the 

 parents during incubation and stated that they relieve each other 

 on duty at short intervals (15 to 40 minutes) and that the eggs are 

 not left uncovered for more than a minute at a time. W. P. Proctor, 

 of Benton Harbor, Mich., coordinates these apparently irreconcilable 

 statements when he writes (MS.): "At some nests, both birds sit on 

 the eggs; at others, the female alone sits. Where the birds take 

 turns, one usually sits from 15 to 25 minutes. At a nest where the 

 female alone sat, there was no regularity; she was off anywhere from 

 an instant to 15 minutes, and once * * * 26 minutes." 



Care of the young is characterized by the usual intense activity 

 of this species, both parents sharing the duties of feeding and brood- 

 ing the young. So unsuspicious, or so preoccupied, are they at this 

 time that they completely ignore human proximity and fly directly 

 to the nest with food. Added to this "dead give away," the growing 

 young in the nest soon become very noisy, so the finding of nests at 

 this stage of development is an easy matter for even an inexperienced 

 observer. 



In the experiment to be described later in the section "Behavior," 

 Maurice Brooks (1933) stated that a feature of the feeding of the 

 young "was the extreme frequency" — 43 feedings in 20 minutes, 34 by 

 the female, 9 by the male. This unequal division of labor does not 

 obtain, I believe, under natural conditions for, although I do not 

 have notes to verify it, my recollection is that the male visits the 

 nest with food almost or quite as frequently as does the female. 



Food brought to the young consists exclusively of animal matter, 

 mostly insects; but so tiny are the separate items that an observer 

 at a distance of only a few feet can seldom identify them. Some- 

 times larger prey is brought in, large enough, according to W. P. 



