The species also occurs widely, but in limited numbers, in Colorado in all seasons and there are photographs of birds referable to this taxon from Utah, Wyoming, Nebraska, and Montana.

Rather, in these birds it indicates a fairly recent allopatric radiation, which has not yet established solid barriers against gene flow on the molecular level; mate choice is conferred by cues of behavior and plumage in the mallardine ducks, and this, under natural conditions, has precluded a strong selective pressure towards establishment of genetic incompatibility.

Although a species of least concern, the Mexican duck is undergoing a slow but marked decline due to destruction of habitat and overhunting.

Concern has been expressed that this combination of factors may ultimately lead to the disappearance of the Mexican duck as a recognizable taxonomic entity (Rhymer & Simberloff 1996, McCracken et al. 2001, Rhymer 2006[dead link‍]), but fairly limited measures such as wetland preservation and preferential hunting of drake mallards would prevent this.

The Mexican duck was listed as endangered species at the United States Fish and Wildlife Service in 1967 but was removed in 1978.