It has been adequately documented that members of these genera closely
resemble one another in their nesting and egg-laying habits. Bent
(1932:407, 417), Davie (1889:157), Goss (1891:242) and Nice (1922:466)
have described the two, white eggs of the clutch of the Mourning Dove.
They have also noted that their nests are composed mainly of twigs and
may be constructed in trees, shrubs or on the ground. The Eared Dove
has nearly identical habits (Bond, 1961:104), and a similar situation
exists with the Zenaida Dove (Audubon, 1834:356; Bent, 1932:418-419).
Like the other species, White-winged Doves lay two white or buffy eggs
per clutch and build frail nests of sticks (Bent, 1932:431; Wetmore,
1920:141; Baird, Brewer and Ridgway, 1905:377).
The point to be made here is simply this: If the species in question
are to be considered congeneric then it might reasonably be expected
that they would display some similarity in nidification and egg-laying.
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.