154 BULLETIN 16 7, UNITED STATES NATIONAL MUSEUM 



On other occasions, when she was invisible on the nest, I could walk 

 to within 10 yards of the tree before she would fly; I believe that 

 at such times she was asleep on the nest. Even after the young have 

 hatched these hawks are very cautious about returning to the nest; 

 repeatedly I have waited in vain for their return, even when well 

 concealed, after they had once seen me; and their cA^es are exceed- 

 ingly keen. They seem to be much more concerned about their own 

 safety than about the welfare of their eggs or young. 



The young hatch at intervals of one or two days and remain in 

 the nest for four weeks or more. Often one of the eggs proves to be 

 infertile, and oftener one of the young dies and is thrown out of the 

 nest, or is forced out of the nest and is killed by the fall. Norman 

 Griddle (1917) writes: 



The number of eggs laid by earh female varies somewliat and seoins to 

 depend, at least to some extent, upon the food supply. In 1917, the six nests 

 imder observation close to the writer's liome, contained but two eggs each and 

 in only one of the six did the parents succeed in rearing more than one young 

 though both were hatched In every instance. The first nest was discovered on 

 May 6, containing two eggs. Other nests with eggs were located as late as 

 June 14. It is difficult to account for the mortality among the young, though 

 it is noteworthy that the deaths occurred while they were still quite small, and 

 that the latest hatched, and consequently smallest, was invariably tlie one to 

 die. Dead examples presented no indication of violence but seemed to show 

 that, in all probability, death was due to starvation, the lack of food being due 

 in its turn to a scarcity of ground squirrels (gophers) and to the unusual 

 number of hawks nesting in the district. 



The curious habit of the old birds in gathering a green leafy bough and 

 placing it in the nest, characteristic of Swainson's hawk also, is very marked 

 in the Red-tail, a fresh bough being gathered at least once daily during the 

 time when the young are small. There hag been some doubt hitherto as to 

 the cause of this habit, but by observing the nestlings I am led to believe that 

 the bough acts as a sun shade, as the young have been seen to repeatedly pull 

 the bough over themselves and crouch beneath it. Doubtless it also acts as a 

 shield and hides the young from their enemies. The leaves are also occasionally 

 eaten. 



As the young develop they acquire a good deal of boldness and defend them- 

 selves with both beak and claws. They have a habit of closely watching the 

 intruder backing up meanwhile at the approach of a hand; then suddenly they 

 leap forward with wings outstretched, and it requires a rapid movement to 

 escape their onslaught. The old birds make no efforts to defend their young, 

 but fly higli overhead uttering loud cries which are, at times, answered in a 

 shriller key by the young beneath. 



The young, when half grown, become very lively, walking about 

 in the nest, stretching or flapping their wings, backing up to the edge 

 of the nest to void their excrement in a long stream far over the 

 edge; the ground under a nest of young hawks is avoII decorated with 

 a circle of white. Their eyes are very keen, and they frequently raise 

 their heads to watch passing birds or to look for the return of their 

 parents. Their weak, peeping notes are heard occasionally, but when 



