2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



Aymar (1935, p. 57) : "a pigeon's pectoral muscles which raise and 

 lower the wing are as much as 50 percent of the entire bird." How- 

 ever, Fisher (1946) made careful comparisons of the volumes of the 

 individual locomotor muscles of vultures preserved in alcohol. For 

 the present study I selected certain groups of muscles used in loco- 

 motion and weighed them in the fresh condition. In addition, the areas 

 used in lift or glide have been determined. 



METHODS 



All specimens were kept in waterproof plastic bags to prevent drying 

 until weighed at the field station. Small birds were weighed on a 

 torsion balance of 120 grams' capacity. Larger ones were weighed 

 on Chatillon spring balances, the most sensitive one for the weight 

 involved being used : 6,000 grams' capacity with 24 grams' sensitivity ; 

 500 grams' capacity with 10 grams' sensitivity; and 250 grams' 

 capacity with 5 grams' sensitivity. 



The bird was spread out on a sheet of paper tacked to a drawing 

 board. A careful outline of the spread wings, tail, and body was 

 traced. The length and median width of the wing were also deter- 

 mined for the calculation of the aspect ratio ( ttt J . Areas were ob- 

 tained later by a compensating polar planimeter. The buoyancy index 



2, — : 



was calculated by the formula, , since area is two- 



Vbody weight 



dimensional and weight is three-dimensional (George and Nair, 1952). 

 After skinning the areas involved, the pectoralis stiperficialis, supra- 

 coracoideus, the rest of the flight muscles (called "rest") except those 

 along the carpus, metacarpus, and phalanges, and finally all the muscles 

 of the lower extremities were removed by means of scalpel and 

 scissors and then weighed. (If there was any delay before weighing, 

 the dissected muscles were kept in a moist chamber.) These muscles 

 were weighed on both sides from at least 200 birds, but thereafter the 

 muscles on one side only were weighed, since the two sides proved to 

 be identical within the limits of error of dissection. The weights of 

 smaller muscle groups have been determined in a few species. Thus 

 the shoulder, upper and lower arm, and upper and lower leg muscles 

 have been separated. Doubling these values gave the totals used in 

 calculations. 



Heart vessels were trimmed close to the organ and both sides cut 

 open, any remaining blood being removed by contact with blotting 

 paper. Weighing was carried out on the torsion balance or on a 



