NO. 2 DIMENSIONS OF FLYING ANIMALS GREENEWALT 



31 



Table 8. — concluded 



Ob- 

 server 



Weight 



gms. 



P 



Flight 



muscles 



Vft.-gms. 



P 



Wing area 



for both 



wings 



cm. 2 



f 



Wing 



spread 



cm. 



K 



Length 



of both 



wings 



cm. 



1 



Table 9. — data from augusto ruschi and 

 crawford h. greenewalt, unpublished 



Wing-beat rate, body weight, and wing length for certain hummingbirds. 

 The nomenclature is from Ruschi, derived, I believe, from Simon. 



The wing-beat rates were measured, some by Ruschi, some by Greenewalt, us- 

 ing a portable stroboscope. In principle a slotted disk was fitted to a monocular 

 so that the slotted portion of the disk passed through the optical axis. The disk 

 was driven by a battery-operated variable-speed motor. A small generator, 

 mounted on the shaft which carried the disk and driving motor, was connected 

 to an ammeter calibrated in revolutions per second. The technique comprised 

 sighting on a hovering bird and adjusting the motor speed until the wings ap- 

 peared stationary. The wing-beat rate was read off from the ammeter connected 

 to the generator. 



The individual readings differ widely in probable error. In two cases — Calli- 

 phlox amethystina $ and Melanotrochilus fuscus — many readings -vrere made 

 and the observed rates are believed reliable to a few percent. For most of the 

 others only one or two readings were possible, and the birds moved so rapidly 

 that only a few seconds were available to bring the instrument to equilibrium. 

 Individual readings could easily be in error by as much as plus or minus 10 per- 

 cent. 



Weights and wing lengths were obtained by Ruschi on the same individuals. 

 These are not necessarily the same individuals for which wing-beat rates were 

 determined. 



For comparison, wing lengths, supplied by Lanyon, American Museum of 

 Natural History, from the literature (principally Hartert), are also given. 



The wing areas are calculated values. Length and area measurements are 

 available for three species (Archilochus colubris and A. alexatidri (Poole, 1938) 

 and Eupherusa eximia (Magnan, 1922)). The averages for these three species 

 result in the equation A = 0.71 P where / is the length in centimeters and A the 

 area of both wings in square centimeters. The areas given in the table are calcu- 

 lated from Ruschi's wing-length measurements using this equation. 



