The Southeastern Arizona Bird Observatory (SABO) is a non-profit organization dedicated to the conservation of the birds of southeastern Arizona, their habitats and the diversity of species that share those habitats through research, monitoring and public education. SABO says:
When to Visit: Southeastern Arizona has something to offer birders and other nature enthusiasts in every season, but if your goal is to see the maximum diversity of Southwestern “specialties” you’ll want to visit between mid-April and mid-September.
Though the first migrants arrive as early as late February, spring migration usually peaks in late April, and a few regional specialties, such as Sulphur-bellied Flycatcher and Rose-throated Becard, don’t arrive until early to mid-May. By late May, the weather is usually uncomfortably warm at midday in the lower elevations, but early summer birding can be very productive in the mountains.
Most non-birders would think you’re crazy to visit Arizona in July or August, but the late summer rainy season is one of the most rewarding times for birding, particularly for hummingbirds, Cassin’s and Botteri’s sparrows, and various Mexican strays.
Fall migration begins as early as late June with the arrival of the first southbound Rufous Hummingbirds and usually peaks between late August and mid-September. Birding slows down by the end of September, and most tropical species such as flycatchers, warblers, tanagers, orioles, trogons and hummingbirds will have departed by mid-October.
Winter (late November-February) is a wonderful time to see many resident birds and wintering northern species such as sparrows, raptors, Sandhill Cranes, and Mountain Plovers, plus the occasional wintering Mexican rarity such as Rufous-backed Robin. The quietest months bird-wise are March and October, but even then first-time visitors to southeastern Arizona will still find much of interest, especially in the lower elevations. —