PLUMAGE OF THE RED-TAILED HAWK 97 



ing, often fill their craws with grasshoppers, that during the after 

 part of the day also enjoy a sail in the air." 



Other writers have noted that the Red-tailed Hawk sometimes 

 feeds upon crows, especially the weak or sickly birds in localities 

 where crows roost in numbers. 



On one occasion while hunting on the farm of Hon. James Wil- 

 son near Traer, Iowa, the writer approached a Red-tail which was 

 apparently being "mobbed" by a score or more of crows. When the 

 writer was almost within gunshot, the hawk started to fly, carrying 

 a dark object which it dropped when shot at, and which proved to be 

 a crow. The hawk escaped, but the crow, though not a shot had 

 struck it, was so pierced both in the skull and thorax by the talons of 

 the hawk that it soon died. 



During the nesting season of the Black-crowned Night Herons 

 (Nycticorax n. naevius) at Eagle lake, in Hancock county, while 

 concealed in the shelter of some oaks where a colony of about two 

 hundred pairs of these herons was located, the writer noticed on sev- 

 eral occasions the commotion caused by the circling of either adult or 

 young Red-tailed Hawks above the trees where nests containing 

 young herons were numerous. The prolonged and startling Whaa ! ! ! 

 Whaa ! ! ! uttered by every adult heron which sighted a ha\vk indi- 

 cated that a dreaded marauder was near. The crows, however, men- 

 aced this heronry much more seriously, since they were ever ready to 

 steal eggs whenever the nests were left unguarded. 



VARIATION AND CHANGE OF PLUMAGE IN THE RED-TAILED HAWK. 



It is interesting to note the range of variation among individuals of 

 borealis and its subspecies. When hard and fast lines are laid down, 

 there is always a specimen to be found which presents one or more 

 characteristics warranting a place in at least two of the varieties. 



Wliile the typical B. borealis is to be found more abundantly east 

 of the Mississippi, it occurs as a rather uncommon resident in eastern 

 Iowa. An adult specimen of this species secured at Sioux City Au- 

 gust 2, 1884 (No. 17490) 'is in the collection of the State University 

 of Iowa. This bird was moulting at the time it was killed and both 

 the partly grown rich chestnut-red tail feathers, as well as the rusty 

 old ones have but a single well-defined subterminal black bar. The 

 tibial flags are lightly washed with buff, but are unmarked. The lower 

 tail coverts are white. 



As for the variety "calurus," while typical specimens of a dark 

 brown or chocolate brown color are not common anywhere in the 



7 



