LARK SPARROW 891 



Building the first nest of the season usually takes the female 3 to 4 

 days, and a full day or more elapses after the nest is finished before 

 the first egg is laid. On June 10, however, I found an egg laid after 

 only 2 days of nest building. Tlie nest was far from complete, and 

 the female added the lining after laying the egg. 



Eggs. — The lark sparrow usually lays four or five eggs, but some- 

 times only three, and more rarely six. They are ovate and have a 

 shght gloss. The ground is creamy or grayish white, with scribblings, 

 scrawls, and spots of black or very dark browns such as "Mars brown," 

 "carob brown," or "mummy brown," with underlying spots of "light 

 neutral gray." The scribblings, most of w^hich are black, are the 

 predominant markings. These tend to concentrate toward the large 

 end where they are often continuous and form a wreath around the 

 egg, frequently leaving the lower part free of markings except for a 

 few scattered spots. Occasional eggs will have a few scrawls of "light 

 neutral gray" mingled with the dark brown or black scribbhngs. The 

 measurements of 50 eggs of the nominate race average 20.1 by 15.9 

 millimeters; the eggs showing the four extremes measure 23.9 by 17. 3 , 

 18.0 by 15.0, and 18.8 by 14.7 millimeters. The measurements of 40 

 eggs of C. g. strigatus average 20.4 by 16.1 millimeters; the eggs 

 showing the four extremes measure 22.9 by 17.8 and 16.8 by I4.O 

 millimeters. 



At Lake Texoma the eggs w^ere usually laid between 5:00 and 

 7:00 a.m. Before laying, the female sits quietly on the nest and can 

 be approached closely without her showing alarm. As she lays the 

 egg she rises sHghtly on the nest; after depositing it she settles rather 

 deeply back into the nest and often shuts her eyes and sleeps for a 

 short time. The newly laid egg is slightly moist and sticky, but it 

 dries in a matter of minutes. 



Incubation. — Incubation is by the female alone. In the early 

 nesting season she does not start incubating until the clutch is com- 

 plete but may return during the day to shade the nest from the sun 

 by sitting rather high on it. In July, females at Lake Texoma, whose 

 earlier nesting attempts were frustrated by snakes or other predators, 

 often started incubating with the first or second egg. 



The female lark sparrow incubates so diligently that she can 

 frequently be approached quite closely before she takes flight. She is 

 particularly reluctant to leave her nest when the sun is shining on it, 

 and on one unshaded nest in an abandoned field I caught the incu- 

 bating bu'd several times by hand. She spends night hours on the 

 nest, and as incubation progresses, leaves it less frequently during the 

 day. At the start of incubation she may leave it for as much as an 

 hour; toward the end she seldom stays away more than half an hour 

 at a time, and I have watched several that stayed on the nest continu- 

 ally for more than 3 hours. 



