NESTS AND NEST-BUILDTNG IN BIRDS 



265 



is held in place by masses of fine rootlets; the lining proper, 

 Nvhich always shows some skeletonized leaves, is of usnea lichen, 

 green moss or fine black vegetable fibres of some sort. 



In marked contrast to most builders of increment nests already 

 referred to, which appropriate all kinds of objects regardless of 

 their form, color, or origin, and mold them in some fashion to 

 their use, stands the stereotyped performance of many mud 



FiGUKE 11 — Nest of the Ameni-au ledsturt (Setophaga ruticilla) illustrating perfect 

 modelling and symmetry of cup, in simple adaptation to support. Diameter 

 of cup, 43 mm. (Iji inches): depth cup, .35 mm. (If inches): diameter nest 

 at rim, 60 mni.( 2f inches): total height, 80 mm. {^\ inches): materials chiefly 

 fine bark strips, coarser without, and secured with spiders' silk: cup molded 

 out of the blades and stems of very fine grass: in gray birch, 12 feet up. Ells- 

 worth, Maine. 



plasterers like the eaves swallows and oven bird of South Amer- 

 ica, or of saliva workers, such as the swifts. The nests of the 

 esculent swiftlet (see fig. 7, part I) are compacted of hardened 

 saliva only, and are highly uniform in size and shape, while the 



