EASTERN MEADOWLARK 63 



blotched, and speckled over the entire surface with different shades of brown, 

 ferruginous, pale heliotrope purple, and lavender; these markings generally pre- 

 dominate about the larger end of the egg, and are rarely heavy enough to hide 

 the ground color. 



In some sets the markings consist mainly of a profusion of fine dots; in others 

 the spots are well rounded and fewer in number; and again they occur in the shape 

 of irregular and coarse blotches, mixed and finer specks and dots; in fact, there is 

 an endless variation in the style of markings. 



The average measurement of a series of two hundred and one specimens in the 

 United States National Museum collection is 27.75 by 20.35 millimeters, or 

 1.09 by 0.80 inches. The largest egg measures 30.78 by 22.61 millimeters, or 

 1.21 by 0.89 inches; the smallest, 21.59 by 18.29 millimeters, or 0.85 by 0.72 inch. 



Ninety-five eggs weighed by G. B. Saunders (MS., see p. 56) had 

 an average weight of 6.6 grams, a minimum weight of 5.4 grams, and 

 a maximum weight of 7.7 grams. Eggs of any one clutch are usually 

 similar in size, coloration, and weight. He found that of 85 eggs in 

 20 nests found at Ithaca, N. Y., 14 eggs, or 15.5 percent, were sterile. 



Incubation. — When an average clutch of five eggs is laid, incu- 

 bation may begin with the deposition of the third, the fourth, or the 

 fifth egg, but more frequently begins with the laying of the fourth egg. 

 The incubation period is usually 14 days, but under certain unusual 

 conditions it may be only 13 or as many as 15 days. 



Although the male has been credited with a share in incubation, 

 Saunders (MS., see p. 56) has never witnessed any such cooperation 

 in the many nests that he has closely observed. Once incubation has 

 begun the female remains on the eggs most of the day, leaving only 

 long enough to feed. The nest is never left at night unless she is 

 frightened by an intruder. During 12 hours and 40 minutes of day- 

 light, one female spent 9 hours and 40 minutes, or 76 percent of the 

 time, on the nest. The longest absences from the eggs were during the 

 middle of the day when the temperature was highest. On cool or 

 rainy days less time is spent away from the nest. 



While incubating, the female is continually active. These activities 

 include listening to songs and sounds of approaching danger, "hum- 

 ming" when the male sings, turning the eggs, feeding on insects which 

 come within reach of the nest, probing in the nest, rearranging nest 

 materials, preening, etc. The female on the nest often responds to the 

 flight song of the male by voicing low, sweet chuckling notes that are 

 unlike any others uttered by the meadowlarks. The softness of these 

 sounds precludes their detection by man at distances greater than 15 

 or 20 feet. The eggs are turned many times during the day, and in 

 the course of 1 hour in the late afternoon a female was observed to 

 turn them five times. The eggs do not hatch in the order that they 

 are laid; for example, the fourth egg may hatch several hours in ad- 

 vance of the third. Individual variation in development causes 

 differences of several hours or even a day in the hatching time. 



