298 BULLETIN 17 0, UNITED STATES NATIONAL MUSEUM 



inches in over-all diameter, the inner cavity was 12 inches in diameter 

 and 2 inches deep, and the outside depth was 8 inches. 



The smallest nest that I have seen was in an old squirrel's nest, 52 

 feet from the ground in the topmost crotch of a tall white pine; it 

 measured only 18 by 16 inches in outside diameter but was deeply 

 hollowed to a depth of 8 inches. The rubbish and dirt had been 

 scraped out, down to the bare branches, and there was no lining 

 except a few downy feathers of the owl. 



My most interesting nest was the one in a historic old beech, in a 

 large tract of heavy, mixed timber, which had been the home of a pair 

 of red-shouldered hawks or a pair of barred owls for many years 

 (pi. 41). This nest was built by the hawks and occupied by them in 

 1907. On April 3, 1909, we were surprised to find that a pair of great 

 horned owls had invaded this territory and taken possession of this 

 nest; this was the first and only time that I have known this owl to 

 usurp a nest of this hawk. The owls had, apparently, brought in 

 some fresh sticks and added a few fresh sprigs of white pine, and the 

 nest was well lined with the downy feathers of the owl; this fresh 

 material may have been added by the hawks, which may have been 

 driven away by the owls after they had started repairing the nest. 

 But Bubo did not long remain in possession of this nesting site, for 

 we robbed the nest, and the barred owls appropriated the nest in 1912. 

 In 1913, 1915, and again in 1928, the red-shouldered hawks, probably 

 the original owners of the nest, occupied their old home. Since then 

 the nest has disappeared. 



Our experience with this nest was not entirely unique, for other 

 somewhat siimlar cases of several species using a nest successively 

 have been recorded. John N. Clark (1887) found a pair of Cooper's 

 hawks nesting in the lofty crotch of a large chestnut, near Saybrook, 

 Conn., in 1884; the following year this nest was occupied by a great 

 horned owl, from which he secured a set of two eggs; in 1886 he was 

 surprised to find that a pair of red-tailed hawks had appropriated the 

 nest; and in 1887 he collected a set of barred owls eggs from this same 

 old nest. It was indeed a popular nest to attract four species in four 

 succeeding years. 



The great horned owl is our earliest breeder, often laying its eggs 

 in February, and sometimes in January, as far north as New England 

 and New York, a month or six weeks earlier than our largest hawks. 

 It seems remarkable that its eggs should be laid before the snows of 

 winter have gone and while they are likely to freeze if left unprotected ; 

 but the reason is obvious when the following facts are considered. 

 The period of incubation is about 28 days, the young remain in the 

 nest about six or seven weeks, and are unable to fly until they are 10 

 or 12 weeks old; this means that if the eggs are laid about the first of 

 March, as they usually are in this latitude, it will be the middle or last 



