R.P. Reynolds
N.J. Scott Jr.
1984
<p class="chapter-para">A collection of 98 breeding Mexican Ducks (<i>Anas platyrhynchos diazi</i>) was made in Mexico from six areas between the United States border with Chihuahua and Lake Chapala, Jalisco, in order to study geographic variation. Plumage indices showed a relatively smooth clinal change from north to south; northern populations were most influenced by the Northern Mallard (<i>A. p. platyrhynchos</i>) phenotype. Most samples were fairly uniform; that from the Río Conchos area in northeastern Chihuahua was noticeably more variable than the others. Soft part coloration is described. Weights varied from 849 to 1,243 g in males and from 647 to 1,264 g in females. Measurements of total, wing, and culmen lengths and bill width were usually significantly larger in males at any one site, but showed no regular geographic trends. Hybridization between<span> </span><i>platyrhynchos</i><span> </span>and<span> </span><i>diazi</i><span> </span>phenotypes may or may not be increasing in the middle Rio Grande and Río Conchos valleys; available data are insufficient to decide. Introgression of the Northern Mallard genome into Mexican<span> </span><i>diazi</i><span> </span>populations may be largely historical owing to recent reductions in the number of migratory Mallards reaching Mexico. A spring 1978 aerial census yielded an estimate of 55,500<span> </span><i>diazi</i>-like birds in Mexico. Populations of<span> </span><i>diazi</i><span> </span>appear to be as large as the available habitat allows; management should be directed towards increasing and stabilizing the nesting habitat; and the stability of the zone of intergradation should be investigated.</p>
application/pdf
10.2307/1366994
en
Oxford Academic
Phenotypic variation of the Mexican duck (Anas platyrhynchos diazi) in Mexico
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