166 BULLETIN 191, UNITED STATES NATIONAL MUSEUM 



nesting activities. A different situation is present early in spring. An 

 example was noted on an early day in March, when, just after 5 :30 p.m., 

 a sparrow hawk flew to a magpie nest in a sycamore. The two magpie 

 owners came immediately and drove away the hawk. The possibility of 

 the hawks taking permanent possession of a nest at this time of day, 

 just before dark, may provide an explanation for the repeatedly observed 

 circumstance that pairs of magpies keep an especially close guard in the 

 tops of the trees over their nests for about half an hour each evening 

 just before dark. 



During the early part of the nesting season whenever sparrow hawks 

 singly or in pairs approached and attempted to enter an occupied magpie 

 nest, one or both of the rightful owners would c.ome immediately and 

 drive them from the vicinity. When smaller birds, for one example 

 a flock of juncos, came near a magpie nest, the magpies paid no atten- 

 tion. They seemed to recognize the nature of the threat offered by 

 sparrow hawks. 



Eggs. — Seventy sets of eggs contained in the Museum of Vertebrate 

 Zoology or collected by W. B. Davis made up a total of 455 eggs, or 

 6.5 eggs per set. Number in a set ranged from five to eight, and the 

 modal number was seven. This indicates a slight tendency toward 

 smaller sets than are laid by the black-billed kind. 



Laying time for this bird is usually the latter part of March. Late 

 nests are rare, and as already indicated they are almost certainly never 

 completed or used in the season they are started. Extreme dates for nests 

 with eggs are March 30 and June 2. All but six of the 70 sets mentioned 

 above were collected in April. This no doubt indicates a shorter, and 

 earlier, season suitable for nesting than that of the black-billed magpie. 



Dawson (1923) described coloration of the eggs as yellowish glaucous 

 or pale olive-buff, finely and rather uniformly speckled and spotted with 

 buffy brown, or citrine drab, or grayish olive, or deep grayish olive. 

 A considerable degree of variation in color was observed by Kaeding 

 (1897) in the 30 or more sets of eggs he collected. Some were heavily 

 blotched with lilac and buffy or purplish brown. Bendire (1895) ob- 

 served that eggs with a greenish tinge in the ground color appeared more 

 frequently in this than in the black-billed magpie. 



Measurements of 195 eggs of this magpie were given by Dawson 

 (1923) as follows: Average 30.8 by 22.4 millimeters (1.22 by 0.88 

 inches) ; index 72.1. Largest tg^, Z7 by 23.4 (1.46 by 0.92) ; smallest 

 26.7 by 20.3 (1.05 by 0.80). Measurements of 62 eggs in the United 

 States National Museum were as follows (Bendire, 1895) : Average 31.54 

 by 22.54 millimeters; largest 34.29 by 22.86; smallest 28.45 by 21.34. 

 Kaeding (1897) has commented on the diversity in shape shown in his 



