blotches, spots, and speckles, principally about the base ; and another is similarly marked about the 

 point, the basal half being immaculate. 



Deep shell-marks are infrequent; but, when they occur, they appear grayish. It is impossible to 

 more than indicate the various patterns. Even between eggs of the same set there is great diversity of 

 markings. Sometimes a plain egg is found in a set, all the others of which are plentifully marked, and 

 vice versa. The color of the markings is subject to considerable variation. Sometimes it is greenish- 

 brown, sometimes yellowish-brown, and sometimes reddish-biwvn ; and these colors run through all shades, 

 from the faintest to the deepest. 



The eggs vary in long-diameter from 2.00 to 2.25 inches, and in short-diameter from 1.60 to 1.80. 

 The majority of eggs measure between 2.10 and 2.20 in long-diameter, and between 1.70 and 1.78 in 

 short-diameter. Incubation lasts, according to Mr. F. W. Carpenter, twenty-seven days. 



DIFFERENTIAL POINTS: 



See Buteo borealis. 



REMAKES : 



Fig. 3, Plate XLIX, represents three eggs of the Red-shouldered Hawk, selected from two sets. 

 One of these was collected by Mr. Charles Dury, near Cincinnati, in April, 1870. The other was col- 

 lected north-east of Columbus, in April, 1883. 



The Red-shouldered Hawk is said to feed largely upon frogs, rats, and mice. Only occasionally does 

 it commit depredations on the poultry yard. The pairs remain mated throughout the year, and do not 

 engage in family quarrels as soon as the brood is reared, as do the Red-tailed Hawks. A pair will 

 occupy the same nest for a number of years, if undisturbed, adding each spring the necessary repairs. 



The Red-tailed Hawk has the same habit of remodeling its old nest year after year, instead of build- 

 ing an entirely new structure. I have known a nest to be occupied the year after I had killed one of a 

 pair which, at the time, had young in the nest; and from this I inferred the remaining bird had found 

 another mate, and had returned to the old home, or else a pair of birds too lazy to build a new nest 

 had taken possession of the old one which had been abandoned. 



Nesting of the Red-shouldered Hawk is often delayed by cold and stormy weather several weeks 

 beyond the usual time. Generally, egg-laying begins about two weeks later than with the Red-tailed 

 Hawk; but, if the spring is wintry, the time between the laying of the two species is considerably 

 lengthened, from the fact that B. borealis cares little for cold and wind when the season of house-keep- 

 ing arrives. I have discovered its eggs when the temperature was below freezing and the ground cov- 

 ered with snow, and have no doubt that many of the sterile eggs found are rendered so by too great a 

 loss of heat. 



A wet season affects materially the appearance of the eggs of both species, as the coloring matter 

 of the markings is quite soluble in water. In a given set of eggs, the brightness and intensity of the 

 markings, as well as the clearness of the ground-color, depend largely upon whether the days during 

 oviposition have been wet or dry. Thus, if showers occur, the eggs exposed will be more dingy, cloudy, 

 and nest-stained than if dry weather prevails. 



176 



