112 BULLETIN 16 7, UNITED STATES NATIONAL MUSEUM 



ACCIPITER COOPERI (Bonaparte) 

 COOPER'S HAWK 



HABITS 



• 



If the sliarp-sliinned hawk is a blood-thirsty villain, this larger 

 edition of feathered ferocity is a worse villain, for its greater size 

 and strength enable it to do more damage. Furthermore, it is much 

 more widely common during the breeding season, being one of our 

 commonest hawks in nearly all parts of the United States. It is 

 essentially the chicken hawk, so cordially hated by poultry farmers, 

 and is the principal cause of the widespread antipathy toward hawks 

 in general. 



In my early bird-nesting days, 30 and 40 years ago, this was one of 

 our commonest nesting hawks ; but for the past 30 years it has been 

 steadily decreasing in numbers. This is perhaps due to constant 

 persecution, but it is largely due also to the marked decrease in the 

 numbers of small birds. I have always considered this and the 

 sharp-skinned hawk as competitive species, each intolerant of the 

 other. I have frequently found one of these Accipiters nesting in 

 the same tract of woods with one of the Buteos, but I have never 

 found the two species of Accipiter nesting in the same tract; and 

 several times I have known cooperi to replace velox in a tract where 

 the latter had repeatedly nested. It is a curious fact that the soli- 

 tary vireo {Lanivireo solitarius) has so often been found nesting 

 in pine woods occupied by a pair of Cooper's hawks as to suggest 

 some significance in the ecology ; I find six such cases recorded in my 

 notes, and once the vireo's nest was within 50 feet of the hawk's 

 nest; we have also noted that we never find the vireo in similar 

 woods occupied by sharpshins ; the reason seems obvious. 



Nesting. — Cooper's hawk is still a fairly common breeder in south- 

 eastern Massachusetts, though my records show that we found three 

 times as many nests during the 20 years previous to 1910 as we 

 have since then. My earliest date for a full set of eggs is April 22, 

 and my latest date for heavily incubated eggs of the first laying is 

 June 3. But I have only six records for April and only three for 

 June, leaving 39 records for the month of May. According to our 

 experience here. Cooper's hawk shows a decided preference for 

 white-pine groves as nesting sites; but it is not nearly so closely 

 confined to this type of woods as is the sharp-shinned hawk. Our 

 notes record 27 nests in white-pine woods, 16 in deciduous woods, 

 mostly oaks and chestnuts, 4 in mixed woods, oaks, chestnuts, and 

 pine, and 1 in a pine on an open knoll among a few scattered oaks ; 

 this last was occupied by a pair that had nested the previous year 

 in a tract of oak woods nearby that had since been cut off. Of these 

 48 nests, 28 were in white pines {Plnus strobus), 11 were in oaks 



