NO. I LOCOMOTOR MECHANISMS OF BIRDS HARTMAN 1 5 



Paridae. — Titmice display restless, acrobatic activity ; they use their 

 feet to hold prey. Their hearts are large (1.35 to 1.49 percent), the 

 flight muscles (23 to 27 percent) and leg muscles (7 percent) fairly 

 so. They are weak fliers, and the wings are typical of perchers. 



Sittidae. — The nuthatches are similar to the titmice in muscular 

 proportions but somewhat different in habits. They not only hop over 

 the bark looking for food, but the red-breasted nuthatch also catches 

 insects in the air like a flycatcher. 



Certhiidae. — The creepers are good fliers, possessing large hearts 

 (1.48 percent) and large wings (buoyancy index, 4.22) and tails 

 (2.35 cm. 2 per g.) 



Troglodytidae. — The members of the fairly large family of wrens 

 are weak fliers and do much running around in exploring for food 

 and in other activities ; as might be expected, their leg muscles are 

 large (10 to 13 percent). Hearts (0.86 to 1.19 percent), flight muscles 

 (16 to 20 percent), and wings (buoyancy index, 3 to 3.39) are 

 moderate in size. 



Mimidae. — Mockingbirds and thrashers show values much like 

 those of wrens but have smaller leg muscles (8.0 to 9.7 percent). Al- 

 though partly arboreal, they also do much feeding on the ground. 



Turdidae. — The above remarks concerning the Mimidae apply 

 also to the thrushes, except that the latter possess large flight muscles 

 (20 to 36 percent). 



Sylviidae. — The smaller gnatcatchers may also be described in 

 much the same way as the wrens, above. 



Motacillidae. — Although the pipits are terrestrial in their habits, 

 running about rapidly, their leg muscles are of only moderate size 

 (6 percent). They are powerful and swift fliers, having fairly large 

 flight muscles (28 percent), large, broad wings (buoyancy index, 3.66; 

 aspect ratio, 1.77), and large hearts (1.57 percent). 



Bombycillidae. — Waxwings have flight power similar to that of 

 the pipits, but their wings are somewhat smaller (buoyancy index, 

 3.29) and narrower (aspect ratio, 2.13). Their hearts are large 

 (1.54 percent). 



Ptilogonatidae. — The silky flycatcher (Ptilogonys caudatus) has 

 a large heart (1.33 percent) and a high buoyancy index (3.80). 



Laniidae. — The loggerhead shrike (Lanius ludovicianus) makes 

 brief, swift flights through the air to seize a victim, but his muscles 

 are moderate in size. 



Sturnidae. — The common starling (Sturnus vulgaris) is a very 

 active bird with rather small, narrow wings (buoyancy index, 3.17; 



