The Eastern Meadowlark in Southeastern Arizona is a non-migratory, local species of the native grasslands. The form here is also known as "Lilian's Meadowlark," and may be split from Eastern soon. Western Meadowlark breeds as far south as the agricultural fields of Marana, northwest of Tucson, and flocks winter here in all weedy and grassy habitats.
Places that have breeding pairs of Eastern Meadowlarks have pairs in the same place in winter. This indicates a sedentary population and that it is unlikely to encounter large flocks any distance away from breeding areas. The only areas in this CBC circle likely to have Eastern Meadowlark are at the far western edge, on the flat, grassy ridges between Negro and Peck Canyons and Ramanote and Toruno Canyons. But there could be some wanderers, and everyone should carefully scrutinize them.
Eastern Meadowlark has the yellow of the center throat sharply delineated from the white of the malar region, with the feather tract line between the two matching the separation of colors. In Western, the yellow bleeds across the feather tract line into the malar region. This can be hard to see in winter and immature birds when the yellow is more creamy and the white of the face a buffy off-white, obscuring the differences in these colors.
Eastern has blacker head stripes and paler background color to the face, but this is comparative and takes eperience.
More of the outer tail feathers in Eastern are purely white, so when seen well in flight, it appears that only the central two tail feathers are dark. On Western, you might be able to see the brown edges on the outer feathers, but they also usually appear totally white; the central brown area of the tail is larger and appears more as a triangle, rather than just the narrow two central feathers. Keep in mind that this is very hard to see well in the field, best viewed when a bird flying away from you and then lands at close range.
Call notes are a great clue. Western actually calls out its own four-letter banding code, "weme," often in flight. It also can give a "chuck" while perched. Eastern is usually silent in flight and gives a rough, rising, fart-like "brzzzit" when perched.