GAMBEL'S WREN-TIT 85 



may be near together or widely separated. The male often sings 

 within 25 feet or less of the nest as he goes to it or leaves, but with 

 equal frequency from other parts of the territory. 



Eggs. — The number of eggs in a set is usually four, but sets of 

 three are not infrequent and sets of five occur occasionally. There is 

 some evidence that the smaller sets are laid by the younger females or 

 early in the season and the larger sets by older females or late in the 

 season. The eggs are usually laid early in the morning on successive 

 days. They are oval and of a uniform pale greenish blue. There are 

 no markings of any kind and the surface is dull. A single brood of 

 young is reared each year, but if the eggs or nestlings are destroyed, 

 the birds will lay as many as four or five sets during the nesting 

 season, which at Berkeley lasts from March to July. 



[Author's note: The measurements of 40 eggs average 18.1 by 

 14.5 millimeters ; the eggs showing the four extremes measure 19.6 by 

 16.0, 16.3 by 14.2, and 17.8 by 12,7 millimeters.] 



Incubation. — The incubation period was 16 days for three sets of 

 eggs that I observed and was probably the same in two other cases. 

 Newberry (1916), however, observed a nest in which the eggs hatched 

 in 15 days. The adults spend at least some time on the nest after the 

 second egg is laid, but in all cases that I observed, continuous incuba- 

 tion began on the day the next-to-the-last ^gg is laid; hence usually 

 on the day the third is laid. In the nest watched by Newberry a lapse 

 of 3 days occurred between laying and the beginning of incubation. 



During the days of incubation the activities of the pair follow a set 

 pattern. The female incubates at night. About 20 minutes after sun- 

 rise (the wren-tit is a relatively late riser) the male sings from his roost- 

 ing perch. The female responds with her call, and both often repeat 

 them. In 10 or 15 minutes the male comes to the nest bush, and when 

 he is within a few inches the female leaves. Her first action is to 

 stretch thoroughly, then in a few moments she is off in search of food. 

 In 15 or 20 minutes she returns, and when she is close to the nest her 

 mate leaves. He sings almost at once and frequently while he is for- 

 aging and patrolling his territory and as he approaches the nest again. 

 Similar exchanges continue throughout the day though the shifts 

 gradually lengthen to 45 or 60 minutes during midday and again 

 shorten toward sunset. Finally when the female returns to the nest 

 within 30 minutes or less of sunset no more changes occur. The male 

 sings often as dusk approaches, and his last songs come from near or 

 on the roosting perch. 



Young. — The eggs of a set hatch within a period of 24 hours. In 

 two nests that I observed, two eggs hatched early one morning, a third 

 later in the day, and a fourth the following morning. During the first 

 35 days the young are constantly brooded by one or the other of the 



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