Figure 2 in The effects of locomotion on the structural characteristics of avian limb bones

Figure 2. Polar section moduli of femora versus section moduli of humeri for all individuals, standardized for bone length (see text). Zp is used here as an estimate of strength in torsion and average strength in bending. The solid line represents equal strength (y = x). Data are presented natural log transformed, and symbols correspond to locomotor categories in Table 1. De, Diomedea exulans; Ac, Aquila chrysaetos; Sm, Spheniscus magellanicus; Ph, Phalacrocorax harrisi; Pa, P. auritus; Ao, Aechmophorus occidentalis; Pg, Puffinus griseus; Ua, Uria aalge; Cc, Corvus corax; Cm, Cerorhinca monocerata; Ta, Tyto alba; Ft, Falco tinnunculus; Gc, Geococcyx californianus; Pr, Phaethon rubricauda; Ra, Rhea americana. The single juvenile rhea was not used in statistical analyses. The long axis of ovals delimiting species indicate isometry. Symbols are as follows, filled symbols, diving birds (those with subaqueous locomotion); triangles (Δ), forelimb-propelled diving; squares (-,Z), flightless taxa. Grebes are indicated by diamonds (Ɨ) and volant cormorants are shown with filled circles (•). The single juvenile rhea is indicated by a cross (+). All other species are delimited by open circles (O).