204 BULLETIN 167, UNITED STATES NATIONAL MUSEUM 



Courtshij). — Mr. Dixon (1928) says that this hawk is so noisy 

 during the mating season that it becomes very conspicuous. 



The usual progr-am is for the bird leisurely to ascend in wide spirals to an 

 elevation of 1500 to 2000 feet above the nest grove, where it will give a few 

 preliminary flaps of its wings, the signal for the noise to begin, and squalling 

 and diving it will descend to the same place from which it started or to the 

 nest grove nearby, in a series of nose dives and side slips. I have seen 

 eagles doing this same stunt without the noise, but have also noted that always 

 in the ofling there is an interloper in the form of another eagle, to whom it is 

 perhaps given as a warning. The Red-bellied Hawk seems to do this stunt 

 for the sheer joy of the thing. 



Nesting. — The same writer, who has "a record of twenty-three 

 nesting locations within a radius of thirty miles of Escondido", says : 



The Red-bellied Hawk, like the Cooper Hawk, selects as a nest site, not some 

 commanding view of its hunting grounds, but a location in a densely wooded 

 grove. Preferal'.ly, the nest is placed about one-half way up the main stem 

 of the tree, upon horizontal limbs and braced against the main trunk. This is a 

 distinctive trait where nesting groves have not been disturbed by clearing 

 of land or been washed away by floods. Rather than leave a chosen hunting 

 ground, however, the hawks will accommodate themselves to almost any kind 

 of a location. Considering their size, the birds build the smallest structure of 

 any of the raptores hereabouts. I have often found nests which from tha 

 ground looked as though they could not possibly contain eggs, let alone conceal 

 a sitting bird, but upon climbing the tree, the bird would leave and the nest 

 would be found to contain four eggs. After incubation is well begun it is 

 almost impossible to flush the sitting bird by any other method than climbing 

 to the nest, and in several instances I have known the bird to remain until the 

 climber reached it. 



The nest is composed outwardly of dead twigs of the trees common to the 

 river bottom, such as sycamore, willow and cottonwood, the inner part of 

 frayed-out bark of the cottonwood and willow. This bai-k makes a soft mat 

 upon which the finishing touches of green leaves and downy feathers are 

 placed. The green leaves are constantly replenished during the incubation 

 period and long after the young are hatched. After incubation has progressed 

 somewhat a large number of downy feathers will make their appearance on 

 and around the nest. This becomes so noticeable in some cases as to be a 

 sure sign of occupancy and one which I have never noticed to such a marked 

 degree in any of our other raptores. 



A pair of hawks often has two or more nests, usually in the same tree or in 

 adjoining trees, and if undisturbed they will remain year after year in the same 

 grove. If an old nest is used, very little is done to it with the exception of relin- 

 ing with bark and green leaves ; so the structure does not take on such a large 

 size as with other hawks. The determining factor in a location seems to be the 

 food supply, and if that is to be had the hawks will use whatever trees are 

 available. I have found nests in willow as low as twenty-five feet from the 

 ground and in large sycamores as high as eighty-five feet. I have never found 

 these hawks using any nest but one constructed by themselves, though I have 

 found other birds using theirs. 



On April 9, 1929, I spent a most interesting day in the field with 

 Mr. Dixon in his territory, visiting seven nests of red-bellied hawks. 



