468 BULLETIN 179, UNITED STATES NATIONAL MUSEUM 



or a dozen and alighted close together with trembling wings extended at an 

 angle from their backs, standing high on their legs to avoid soiling their feathers. 

 After alighting they leaned over, filled the mouth with mud with one or two 

 sharp digs and then rose to fly back up the steep slopes to the colony. Males 

 frequently alighted on the backs of the females as they gathered mud and 

 copulation took place while the birds were on the ground. 



Nesting. — The nests of the cliff swallow are cleverly constructed of 

 pellets of mud or clay, are roofed over, and generally assume a flask, 

 retort, or bottle shape with a narrow entrance leading into an en- 

 larged chamber. The protruding neck of the nest varies greatly, from 

 some .5 or 6 inches long, or even longer, to others that have no neck, or 

 even to an open structure approaching the barn swallow type of nest. 

 The cliff swallow may strengthen the walls of its plastic home by the 

 use of straws and horsehair, but such materials are not so freely used 

 as they are in the nests of the barn swallow. As a result the former 

 are more friable and are subject to a greater amount of erosion and 

 breaking, especially if they become dampened during times of heavy 

 rainstorms. The chamber of the nest is scantily lined with a few dried 

 grass stems to which a few feathers and other materials are sometimes 

 added. 



The cliff swallows are gregarious in their nesting habits, and it is 

 exceptional to find isolated nests far distant from others of the species. 

 The primitive nesting sites of this swallow are in various situations 

 afforded by bluffs, cliffs, and the perpendicular walls of deep gorges 

 m remote mountainous sections of its nesting range, and many of them 

 continue to nest in regions where such situations prevail. Many of the 

 largest colonies, some of them comprising thousands of nests, are lo- 

 cated on cliffs. The cliff swallow, however, is a plastic, adaptable 

 species that has been quick to accept new and very different situations 

 provided by civilized man and thus has materially increased its range 

 as well as its numbers. They have accepted the great concrete dams, 

 erected by man in the construction of power projects, which are the 

 nearest approach to the primitive sites used by these cliff dwellers. 

 Today, especially in the eastern parts of its nesting range, this swal- 

 low is associated with the eaves of houses and barns, where its friable 

 nests are better protected from rainstorms, but this has also made 

 them subject to greater molestation by such enemies as the English 

 sparrow. In New England it is unusual to find them nesting on cliffs. 

 Although I have \'isited more than 50 populous colonies in New Eng- 

 land and the Maritime Provinces I have seen only one located on a 

 cliff. So general has this change in habitat been established that the 

 name eaves swallow is considered a much more appropriate designa- 

 tion of the species. In cases where the birds have been given human 

 encouragement the colonies located on barns often vie in numbers 

 with those located on cliffs. Christensen (1927) has published a photo- 



