NO. I LOCOMOTOR MECHANISMS OF BIRDS — HARTMAN 19 



teroceplwla, Thraupis espicopus, Piranga leucoptera, Habiafuscicauda, 

 and Saltator maximus. In only two species, Jacana spinosa and Vireo 

 philadelphicus, were the pectoralis plus supracoracoideus larger in the 

 female than in the male. 



Latitude. — The pectoralis plus supracoracoideus muscles were rela- 

 tively heavier in Panama specimens of Florida caerulea and Cathartes 

 aura than in birds of the same species collected in Florida. 



FLIGHT MUSCLES 



irmt 



800 



600 



400 



ACCIPITRtDAE , NUMIDIOAE 



THRESKIORNITHIDAE \ * -CRACIDAE 



FALCONIDAEOy \ •— ANHINCIOAE 

 aOOr- ARDEtDAE-—-^> *-PHALACROC0RACIDAE 



ANATIDAE- Jv^ARAMIDAE 

 C0CHLEARM0AE~~. VHI T0N J ? &E 



LARIDAE 



TINAMIDAE-* «V • 

 NYCTIBIIOAE ^-PHASIANIDAE 



1»-RYNCH0PIDA£ 



I 00 

 60 



60 



40 



P.ELECANIDAE- 

 CATHARTIDAE. 

 PAND10NIDAE-* 



STRIGtDAE 



CHARA^^a'!*// ^-R AMPH AST I D AE 



80 r TYRANNIDAE/ ^-CORVIDaE 



PSITTACIDAE // ^Z— A LCEOI N I DAE 



COTINGIDAE\ )/* t HE LI ORNI THIOAE 



TROGONIDAE\\l;{- BUCCONIDAE 



C0LUM8IDAE V\»*0- JACANIDAE 



SCOLOPACIDAE 1/ Vp- on 



T U R I A E I »* <... u c u ,f A E 



BOMBYCILLIDAEl • ^,,L, U mnn»r 

 rvn abu in»c \ 1 *.*■—__ C APRI MULGI DAE 

 CYCLARHIOAE \1 *-<~--— , M I M I D A E 

 P.LOCEI0AE A VJI. -FRINGILLtDAE 



PICIDAEv\\*' ^FORMICARHDAE 

 FURNARIIDAE-,^ \ -j^^-'CAPI TO.NI O'AE 



PARIDAE • i»^"~"L-RALLlbAE 



SLTTIOAE f ICTERIOAE 



PIPRIOAE-S*! THRAUPIOAE 

 PARULIQAE-'"\COEREBI0AE 



S . ^VIREONIDAE 

 MOTACILLIOAE V\ 



•\ TROGLODYTIDAE 

 "IRUNDINIOAE 



DENDROCOLAPTIDAE 

 TROCHILIOAE* •'CERT.HIIOAE 



^SYLVIIOAE 



■ ' ' ' t . ■ t t I t 



6 6 10 eo 40 60 100 200 400 600 1000 2000 4000 

 BODY grams 



Fig. i. — Selected plottings (see asterisks in table i) of upper extremity muscle weights 



against body weights (log scales). 



Altitude. — In Piaya cayana and Crotophaga ani both flight muscles 

 and pectoralis plus supracoracoideus were relatively heavier in high- 

 altitude birds (4,300 ft.) than in these species collected on the Rio 

 Chagres. Likewise the pectoralis plus the supracoracoideus were 

 heavier in Pteroglossus frantsii (collected at 4,300 ft.) than in 

 Pteroglossus torquatus obtained on the Rio Chagres. 



For an overall comparison of the flight muscles, selected species 

 from each family have been plotted on a logarithmic scale (fig. 1). 

 If one draws a line through the values for the heavier birds, it will 



