AMERICAN WAKBLEK.S. 



125 



calchers, they differ from them in not having the basal tufts, these being conspicu- 

 ous in the flycatchers ( see Fig. 56, E, skull of Redstart, and compare with Fig. 57, 

 A, upper mandible of Least Flycatcher; both are life-sized figures showing the ric- 

 tal bristles; also see Fig. 56, G, rictal bristle of Redstart somewhat enlarged, and 

 H and J, base of bristles ot the same greatly enlarged: also N, base of bristle of Ca- 

 nadian Warbler; compare with I, bristle of Least Flycatcher, somewhat enlarged, 

 and P, base of same bristle greatly enlarged). The function of rictal bristles ap- 

 pears to be to aid birds which feed upon flying insects in capturing their prey. These 

 bristles are, of course, modified feathers, hence we should naturally expect to find 

 I hem farthest departed from typical feathers in birds that have possessed them the 

 longest lime. 



Fig. 56. 



A B 



Structuue of Redstart:- A, terminal e.'cpansiou of iiircula; B .sternum; D, section of skull; E 

 .skull, side view; F, same from above; G, rictal bristle; H and J, the same greatly enlarged; O. oostal 

 process of sternum; Q, lower side of upper mandible; II, section of stomach; V, tongue ; W, stomach 

 and other organs; X, stomach and convolutions of intestine; Y, oil sac; M, base, L, back, K, top. of 

 brain. N, rictal bristle of Canadian Warbler. 



Least Flycatcher :- I, rictal bristle: P, same much enlarged ; C, section of skull; R, sternum; S, 

 terminal expansion of lurcula; T, costal ijrocess ot sternum. Figs. A, C, D, G, H, I, J, N, O. P, Q, S, T, 

 and V are enlarged. 



The skull is small and narrow, .60 long from base of bill to occiput and .46 

 broad. Its upper walls are, as in other warblers, double, the upper and lower por- 

 tions being supported and attached together by tiny pillaretts, which are in a few 

 cases forked, but are mostly single. In the flycatchers, all of which have more or 

 less spongy skulls, and thus also with double walls, these pillaretts are seldom if 

 ever, si ngle, hut are much branched, the branches often extending outward from the 



