Robert L. Merz

“ Probably the Mourning Dove has failed to adapt to nectar-feeding as yet, and the White-winged Dove is the primary exploiter of this food niche. It should be noted, also, that the head of the Mourning Dove is smaller than the white-wing's, and perhaps there is no need for an elongated beak for reaching deeply into the flowers.
The lengthened bill should produce no difficulties in protraction of the upper mandible and depression of the lower for the reason that in the dove there is no known resistance offered to these movements. ”

“ The anterior margin of the origin is at the point where the mandibular ramus of the trigeminal nerve enters the mandible. Posteriorly the origin is bounded by the insertion [Pg 528] of M. adductor mandibulae posterior, and ventrally by a ridge that is situated about halfway down the medial side of the mandible. The insertion is by aponeurosis on the tip of the orbital process of the quadrate and fleshily on the anterior surface of the same process. The aponeurosis extends about three-fifths of the distance along the muscle and it is dorsal or superficial to all of the fibers. ”

“ There is no lifting action involved in contraction of the depressor muscle in doves for two reasons— (A) the origin of the muscle is situated much too far posteriorly on the skull, and, more important, (B) the quadrate is not hinged for vertical movement. As will be discussed later, it moves only in a horizontal plane.
M. pseudotemporalis superficialis.—Like M. adductor mandibulae, this muscle performs only the one function of adducting the lower mandible, and like M. pseudotemporalis profundus it is a synergist of that muscle. ”

“ In birds lacking resistance to abduction of the lower mandible, as in doves, it is nevertheless necessary for a slight postarticular process to remain for the insertion of a small depressor muscle which, as mentioned previously, is necessary to counteract the relaxed adductor muscles of the lower jaw. ”

“ 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. ”

“ The jaw musculature of doves is not an imposing system. The eating habits impose no considerable stress on the muscles; the mandibles are not used for crushing seeds, spearing, drilling, gaping, or probing as are the mandibles of many other kinds of birds. ”

“ If their habits varied considerably it would not necessarily mean that their relationship was more distant, but similarities can usually be considered indicative of affinities because they are the phenotypic expression of the partially unaltered genotype of the common ancestor. ”

“ Perhaps plumage patterns are the most widely used characters for determining generic relationships of birds. Ridgway (1916:339-385) followed the columbid classification of Salvadori (1893) using plumage patterns and body proportions to distinguish between the genera. In the genus Zenaidura he included the unique specimen Zenaidura yucatanensis, and he placed auriculata in Zenaida. The White-winged Dove was referred to a separate genus, Melopelia. He described the genus Zenaidura in the following manner:
"Plumage of head, neck and under parts soft and blended ”

“ However, M. pseudotemporalis profundus could produce a more powerful grip because it takes origin farther anteriorly on the lower mandible.
M. protractor pterygoidei.—Contraction of M. protractor pterygoidei pulls the pterygoid anteromedially and causes it to slide forward along the sphenoidal rostrum. This action aids in protraction of the upper mandible. ”

“ Edgeworth, F. H.
1935. The cranial muscles of vertebrates. Cambridge Univ. Press, viii + 493 pp., 841 figs.
Engels, W. L.
1940. Structural adaptations in thrashers (Mimidae: genus Toxostoma) with comments on interspecific relationships. Univ. California Publ. Zool., 42:341-400, 24 figs., 11 tables.
Fisher, H. I.
1955. Some aspects of the kinetics in the jaws of birds. Wilson Bull., 67:175-188, 4 figs., 6 tables.
Gadow, H.
1891. Vogel: I. Anatomischer Theil. Bronn's Klassen und Ordnungen des Thier-Reichs. C. F. Winter, Leipzig, 6:1-1,008, many figs., 59 pls. ”