THE NEST 71 



The Nest 



Enemies of Nesting Birds. It will add to our appreciation of a 

 bird's resources and most assuredly to our sympathy with birds, if 

 before discussing, their nesting habits we merely mention some of the 

 enemies and dangers which threaten birds at this season. These are 

 of two kinds; first, the elements; second, predatory animals including 

 parasites. High winds, heavy rains, prolonged wet or cool periods and 

 hail-storms are among the weather phenomena often fatal to the life 

 of the nest; while chief among the animals that prey upon the eggs or 

 young of our birds, are Crows, Jays, Crackles, cats, squirrels, opossums, 

 minks, weasels, skunks, snakes, and man, who either directly, as an 

 egg collector for the table or cabinet, or indirectly, in mowing fields, 

 clearing hedgerows and in other ways, has won a prominent place among 

 the enemies of nest-life. 



With such an array of adverse conditions and relentless foes, the 

 bird which reaches maturity may be said to have escaped nine-tenths 

 of the dangers to which bird-flesh is heir. One realizes, therefore, how 

 important it is for birds to select a site, build a nest,- and care for their 

 young in a way which has proved to be most desirable for their species; 

 and how readily imperfect inheritance of the proper activities or in- 

 ability to conform to new conditions may mean failure to rear a brood, 

 and in the end extinction of the species. 



Nesting Site. The nature of a bird's nesting site appears to be 

 determined by (1) the necessity for protection; (2) condition of the 

 young at birth; (3) temperament, whether social or solitary; (4) 

 habit, whether arboreal, terrestrial or aquatic; (5) haunt, whether in 

 woodland, field, marsh, etc. 



Protection may be secured by hiding the nest, by placing it in more 

 or less inaccessible situations in trees or on cliffs, or by frequenting some 

 isolated islet uninhabited by predatory animals. As I have elsewhere 

 said ("Camps and Cruises of an Ornithologist," pp. 35-37), "So far as my 

 experience goes, all colonial ground-nesting birds breed only on islands." 

 Auks, Murres, Skimmers, Petrels, Tropic Birds, Gannets, Cormo- 

 rants, Pelicans and Flamingoes are examples among North American 

 birds, with which Bank Swallows appear to be the only exception. It 

 is less to their terrestrial habit than to their gregariousness that we must 

 attribute the necessity of an island home for these birds. When nesting, 

 all the individuals of a given species, which at other seasons are scat- 

 tered over a wide area, are focused in a small space. To find one nest 

 is to find all, and to a large degree the fortune of one nest is also the 

 fate of its neighbor. 



Even when arboreal, colonial birds like Herons, Spoonbills, Anhingas, 

 and Cormorants usually breed in trees growing in water and which are 

 thus insulated. The birds just mentioned are all exceptions to the rule 

 that terrestrial feeding birds usually nest on the ground, while arboreal 

 feeders nest in trees. But here the condition of the young at birth exerts 



