166 BULLETIN 19 7, UNITED STATES NATIONAL MUSEUM 



areas. A wreath of spots about the large end rarely is present. Out 

 of 150 eggs of Lanius ludovlcianus examined by me, 6 instances of 

 reversal of the color pattern, that is, heavy pigmentation on the small 

 end of the egg, have been noted. Four of these examples were in the 

 same set of eggs. 



The measurements of 97 eggs average 24.1 by 18,5 millimeters; 

 extreme measurements are 26.9 and 22.0 for length and 19,4 and 17.3 

 for width. The average and extreme weights of 100 eggs weighed by 

 Hanna (1924) and myself are : 4.64 gm. (5.7-3.6). 



Incubation. — The female alone incubates and begins to cover the 

 eggs usually with the laying of the next to last egg of the set. The 

 incubation period is 16 days. 



The female leaves the nest only for short intervals and depends 

 largely upon the male for her supply of food. Usually the female 

 attempts to return and cover the eggs within five minutes after having 

 been flushed from the nest, unless she is an especially wary individual. 

 When settling upon the eggs the shrike usually spends several seconds 

 in moving about rather vigorously, adjusting the clutch so that it will 

 be well covered and included between the two ventral feather tracts 

 on the breast and belly. The incubating bird faces in various direc- 

 tions while on the nest, often turning toward an observer as if better 

 to watch for danger. It has been repeatedly recorded in my notes 

 that eggs in sets are arranged in a definite order in the nest according 

 to the direction in which the bird previously had been facing during 

 incubation. Sets of six eggs usually are arranged in a double row of 

 three, the row paralleling the long axis of the bird's body. The align- 

 ing of the eggs in a double row appears best suited to the brooding of 

 a large sized set by a bird of the narrow proportions of a shrike. 



The male feeds the female while she is either on the nest or in the 

 near vicinity of it when she has left incubation to meet the male. The 

 food is not placed in the mouth but, as during the period before in- 

 cubation, is snatched from the male's bill and is swallowed at once 

 or, if necessary, first is broken into pieces or impaled. When fed 

 while incubating, the female either stands up in the bottom of the 

 nest or else remains settled on the eggs and allows the male to approach 

 close enough to enable her to reach the food in his bill. Wlien the 

 pair is not at the nest, the male usually does not approach the female 

 but waits for her to come and take the food from him. 



At a nest at Pinole, between 6 and 6 : 30 a. m., the female was fed 

 five times. On this date, March 31, 1930, sunrise was at 6: 16 a. m. 

 Later in the morning the male did not appear at the nest more fre- 

 quently than every half hour, and on a later date in the afternoon, 

 45 minutes elapsed withovit feeding. Occasionally the female may 

 forage for herself within 50 yards of the nest tree ; especially is this 

 done if the male is absent. An estimate of the source of the food 



