Migration Info The actual winter range of this species is not clearly known. Its primary habitat is middle-elevation forests in the northwestern Andes, but there is some debate as to whether this species is also prevalent in the Amazon lowlands. The major spring migratory route is across the western Gulf of Mexico; the first birds appear on U.S. soil in late March, and peak numbers occur along the Gulf coast in early April. The duration of their stay along the coast is weather-dependent: If there is fog or a significant headwind, they stay; clear weather or tailwinds cause them to move inland. The rate of northward progress in the East is tied to foliage development in deciduous forests; Scarlet Tanagers prefer to remain in areas with a well-developed upper canopy.