The Mexican duck, a large, brown-bodied puddle duck found from central Mexico into the southwestern United States, had long been considered a subspecies of the mallard. But last June, the American Ornithological Society deemed that Mexican ducks are a separate species, now known by the scientific name Anas diazi.
After much DNA analysis, genetic studies indicate that mallards, black ducks, mottled ducks and Mexican ducks are closely related, yet distinct. And because black ducks and mottled ducks are considered by scientists to be separate species from mallards, ornithologists have decided that Mexican ducks should be their own species, too.
For the record, the AOS had previously decided in 1983 that Mexican ducks were a subspecies of the mallard based on extensive studies during the 1970s by John Hubbard of the New Mexico Fish and Game Department. Now, the AOS has reversed that decision in part because a 2017 study showed “genetic evidence suggests that hybridization is not as widespread as previously believed.”
Mexican ducks breed in northern and central Mexico, west-central Texas, southern New Mexico and southeastern Arizona, and seem to be expanding their range. In Sept. 2011, Dr. Chris Nicolai, staff biologist for Delta Waterfowl, was the first person to band a Mexican duck in Nevada. Nicolai worked for the U.S. Fish and Wildlife Service in Reno, Nevada, before joining Delta’s staff last year.
“I was leading a field trip with 40 undergraduate wildlife students banding ducks,” he recalled. “I heard a student ask, ‘Why does this hen have a yellow bill?’ and I instantly turned around. Sure enough, it had all the indications of a Mexican duck.”
Mexican ducks, while not common, are legal to hunt. In Arizona and the Central Flyway portion of New Mexico, regulations allow two hen mallards or “Mexican-like ducks” daily, while Nevada and California don’t distinguish Mexican ducks separately in the bag limit — technically hunters could shoot a full limit of seven per day. Meanwhile, Texas regulations lump mottled ducks, black ducks, Mexican-like ducks and their hybrids into a category called “dusky ducks,” and the limit is one dusky duck daily. —