though this is practiced infrequently. Distribution and habitat Their range includes almost all of Mexico, extending north into the southwestern United States, and south to scattered portions of Central America, and parts of northwestern and central South America. It has ranged as far north as Canada. North American populations are generally resident, migrating only at the edge of the range. South American populations, especially those further south, may make long migrations to the northernmost parts of the Brazilian Amazon. This reflects a tendency to overwinter in areas where the temperature does not go below . Migrations may extend up to . North American populations generally migrate by late August and return between February and April. Their ability to migrate likely aided their wide colonization of the Americas. Vermilion flycatchers prefer somewhat open areas and are found in trees or shrubs in savanna, scrub, agricultural areas, riparian woodlands, and desert as well, but usually near water. They range up to elevations of . A study in Arizona found that their preferred breeding range included cottonwood or mesquite tree canopies, although Fremont cottonwoods were not favored. Goodding's willow was preferred as a nesting site where found. Understory plants mainly consisted of invasive Cynodon dactylon grass. Behavior Vermilion flycatchers are generally solitary, though they may form small flocks of not more than five individuals during winter. They spend most of their time in trees perching, landing on the ground only rarely to catch insects. They do not generally hop, preferring to fly to get around, and glide only infrequently. Breeding and nesting Vermilion flycatchers are socially monogamous, but engage in extra-pair copulation. Both males and females will breed with individuals other than their monogamous mate. A 2002 study found that 11% of offspring were from extra-paternal copulation. They also practice intra-specific brood parasitism, where females lay their eggs in the nest of another vermilion flycatcher. Between 9.5 and 19% of offspring were the result of brood-parasitism. Females often spend long times away from the nest, which enables others to lay eggs in their nests while absent. This may simply be a form of parasitism, wherein the pair whose nest is being parasitized gains no benefit. But for promiscuous birds, this may provide some genetic fitness. For a male mating with many females, and those females laying many of their eggs outside of their nest, this increases the odds that a promiscuous male's offspring