SUMMARY AND CONCLUSION
The avian genus Zenaida is currently considered to be distinct from the genus Zenaidura by most columbid taxonomists. The jaw muscles of six Mourning Doves (Zenaidura) and five White-winged Doves (Zenaida) were investigated as to differences and similarities that might clarify the relationships of the genera. The sizes and proportions of skulls were also considered in 37 Mourning and White-winged doves and two Eared Doves. Larger size of M. pseudotemporalis profundus, the muscle that functions simultaneously as an adductor of the lower jaw and retractor of the upper jaw, in the White-winged Dove was the character found in the jaw musculature that could be used to support the contention that Zenaidura and Zenaida represent distinct genera. Larger size of this muscle in the white-wing seems to be related to its elongated beak. The long beak apparently is used for nectar-feeding in flowers of the Saguaro Cactus.
Excluding the beak, skulls of the white-wing and Mourning doves are of nearly the same shape. Previous investigators have shown that in Zenaida and Zenaidura plumage patterns are similar, nesting habits and eggs are nearly identical, blood proteins are similar, and one "intergeneric" hybridization in nature is known.
Consequently, it is concluded that species of the two alleged genera are congeneric, and I agree with Goodwin (1958) that the genus Zenaida (Bonaparte, 1838:41) should include the Mourning Dove, Eared Dove, Socorro Dove, Zenaida Dove, and White-winged Dove. Their Latin binomina are Zenaida macroura, Zenaida auriculata, Zenaida graysoni, Zenaida aurita, and Zenaida asiatica, respectively.
Fig. 1. Medial view of left ramus of lower mandible of Mourning Dove. × 2-1/2.
Fig. 2. Lateral view of right ramus of lower mandible of Mourning Dove. × 2-1/2.
Fig. 3. Dorsal view of lower mandible of Mourning Dove. × 2-1/2.
Fig. 4. Ventral view of lower mandible of Mourning Dove. × 2-1/2.
Fig. 5. Dorsal view of right quadrate of Mourning Dove. × 5.
Fig. 6. Dorsal view of right pterygoid of Mourning Dove. × 5.
Fig. 7. Ventral view of right quadrate of Mourning Dove. × 5.
Fig. 8. Ventral view of right pterygoid of Mourning Dove. × 5.
Fig. 9. Right lateral view of skull of Mourning Dove. × 2-1/2.
Fig. 10. Ventral view of skull of Mourning Dove. × 2-1/2.
Fig. 11. Cross section of skull of Mourning Dove; anterior view. × 2-1/2.
Fig. 12. Dorsal view of right quadrate of Mourning Dove showing movement which protracts the upper mandible (broken line). × 5.
Fig. 13. Right lateral view of the jaw musculature of the White-winged Dove; superficial layer, × 5.
Fig. 14. Right lateral view of the jaw musculature of the Mourning Dove; superficial layer. × 5.
Fig. 15. Dorsal view of the jaw musculature of the White-winged Dove (right side); superficial layer. × 5.
Fig. 16. Dorsal view of the jaw musculature of the Mourning Dove (right side); superficial layer. × 5.
Fig. 17. Dorsal view of the jaw musculature of the White-winged Dove (right side); middle layer. × 5.
Fig. 18. Dorsal view of the jaw musculature of the Mourning Dove (right side); middle layer. × 5.
Fig. 19. Dorsal view of the jaw musculature of the White-winged Dove (right side); deep layer. × 5.
Fig. 20. Dorsal view of the jaw musculature of the Morning Dove (right side); deep layer. × 5.
Fig. 21. Ventral view of the jaw musculature of the White-winged Dove (M. depressor mandibulae not shown). × 5.
Fig. 22. Ventral view of the jaw musculature of the Mourning Dove (M. depressor mandibulae not shown). × 5.