Mexican Duck, Anas diazi

Mexican Duck, Anas diazi. Birds photographed in the greater Mexico City area, March 2021. Photographs and identification courtesy of Marina Sutormina, Stockholm, Sweden.

Mexican Duck, Anas diazi. Photograph taken in the coastal area of Yavaros, Sonora, March 2019. Photograph and identification courtesy of David F Smith, Alamos, Sonora.

The Mexican Duck, Anas diazi, is a dabbling duck and a member of the Anatidae Family of Duck, Geese and Waterfowl, which has one hundred seventy-four members placed in fifty-three genera, and one of thirty-one global species of the Anas Genus. They are also known in Mexico as ánade Mexicano.

The Mexican Duck is medium to large and stocky in stature. The sexes are similar. They have a broken streaky pattern of buff, white, gray, or black on brown feathers, whitish outer tail feathers, contrastingly pale belly and undertail coverts, and a prominent dark eyeline. Their upperwing has iridescent blue to violet-blue speculum bordered with a white line at leading edge and trailing edge. Their bill is broad and varies from bright yellow to orange or yellowish orange with dull black tip. The bills of the females are duller than the bills of the males; their iris is dark brown; and, their legs are dull brownish to orange and their feet are orange-red to vermilion orange.

The Mexican Duck are found in close proximity to permanent rivers, large lakes and irrigation developments and are found in areas that have annual wet and dry cycles of seasonal precipitation with generous rainfall from June to October and limited amounts of rain through the winter months starting in November and continuing into May. They are found in large flocks, comprised primarily of paired birds, during the dry period, which quickly disperse for nesting. They are opportunistic omnivores that feed on aquatic invertebrates, insects, insect larvae, cereal crops, seeds, and terrestrial earthworms. The Mexican Duck is poorly studied and very little about their biology and behavioral patterns has been documented.

The Mexican Duck is very easily confused with the Gadwall, Mareca strepera (white speculum, grayish-brown tail, plain gray face) and the female Mallard, Anas platyrhynchos (larger, lighter with more varied body coloration).

The Mexican Duck is ENDEMIC to Mexico and found in the interior highlands of central and northern Mexico from the United States border extending westward to northeast Sonora and Chihuahua, east to Nuevo León and San Luis Potosí and south to Michoacán, México, Tlaxcala, Puebla, and Oaxaca. They are known to be short to medium distance migrants moving between breeding and wintering grounds in annual cycles; however, the majority are sedentary.

From a conservation perspective the Mexican Duck has not been formally evaluated. The long-term viability is threated habitat destruction and degradation caused by human development of their breeding and wintering grounds. Their populations are small and estimated to be on the order of 130,000 individuals.