Sexual Dimorphism in Mexican Lentils
Mexican lentils are characterized by sexual dimorphism in the color of plumage: the head, chest and back of the males are colored red, with a motley abdomen and brown wings and tail, while females are simpler - mottled from below and brown from above. Young males resemble females in color [2] .
Other characteristics of the species are common for males and females: a conical beak, a long non-bifurcated tail (one of the main visible differences from purple lentils and Cassin lentils ) and characteristic singing, often in flight [2] . The total body length is about 14 cm (females are approximately 1.3 cm shorter than males), tail length is 6.6 cm, average weight is from 19 to 22 g [3] . Nevertheless, the wide geographical distribution and diverse habitat led to a large phenotypic variation in appearance and physiology [4] .
Mexican lentils are monogamous. Pairs form in the winter, before the nesting season begins. In the process of courtship, the male demonstrates the “flight of the butterfly”, soaring upwards by 20-30 meters, and then starting a slow sliding descent, accompanied by loud singing. It is noted that females prefer males with a brighter coloration of the head [3] .
The nesting season lasts from March to August, and during this time the couple manages to make up to six clutches, however, chicks usually come in no more than three. The nest is open, cup-shaped [2] . In clutch, as a rule, from three to six bluish or greenish-white eggs weighing about 2.4 g each; the incubation period is 12-17 days. Only the female incubates. The chicks fly from the nest in 12-19 days, after which the female builds a new nest and makes a new clutch, and the father continues to feed the chicks for some time. The maximum recorded lifespan of Mexican lentils in the wild is 11 years and 9 months [3] .
Mexican lentils are daytime birds. They feed mainly on grains, a small part of the diet is fruits and insects. Unlike other types of lentils, Mexicans can feed on the ground, although they usually do this only in large flocks or in the immediate vicinity of high perches. The main natural enemies are hawks and domestic cats; small rodents, rats, snakes, raccoons, jays and crows can destroy nests [3] .
Mexican lentils are one of the most common types of North America: the total number is estimated at 21 million individuals [3] . It is found throughout the United States and Mexico , as well as in southern Canada ; the total distribution area of the species is more than 20 thousand km² [5] . At the same time, this species is not indigenous to the northern part of the continent: the offspring of several specimens brought from California, released in 1939 in New York, spread, occupying one of the widest ecological niches among modern bird species. If the original habitat of Mexican lentils were deserts and arid areas in the southwestern part of the continent, now they settle on the ocean coast, and on the southern border of the taiga, and in megacities [4] . The northern populations, unlike the southern ones, have mastered a migratory lifestyle and spend the winter in the southern regions of the United States. In addition to the continental United States and Canada, Mexican lentils were also brought to Hawaii [3] .
In eastern North America, Mexican lentils nest in the vicinity of human habitation, usually in cities, in the crown of middle-tier trees [2] . In their original habitats, in the southwest, they can be found in deserts and steppes, on river banks, in bushes and in open coniferous forests [3] .
Distribution from 1958 to 2008
