No Better Time than the Present

By the time you read this summer’s grip will be loosening, giving way to autumn’s perfect start. Postseason baseball will be on the horizon, and the fall bird migration will be hitting its stride. Perfect weather, playoff baseball and the rush of migration all combine to make September my favorite month.

It often starts subtly: a rufous hummingbird here, maybe a hermit warbler there. By late August, any given day in the field can produce a diverse and rewarding birdwatching experience. Even better, the next day in the same spot can be completely different. As species migrate, they move in concentrated ‘waves’ of their peers, even among species that don’t normally flock. One day you might see a surge of Wilson’s warblers, the next they could be replaced with Townsend’s warblers. These peaks represent the bulk of a population sweeping along its migratory route.

These waves are golden opportunities to study one species in depth — males, females, juveniles and different plumages all in one place. Closely related species often travel together as well. For example, warblers in the genus Setophaga can often be found near each other, making it easier to compare similar species. While male Townsend’s and hermit warblers are distinct, a fleeting view of a female can trip up even experienced birders.

Mixed flocks deserve careful attention year-round. Birds that end up far from their normal range often join groups of similar feeders for safety. A black-throated green warbler, for example — also Setophaga — might tag along with Townsend’s warblers. The two are near counterparts, separated by the Rocky Mountains. At a glance, they may seem alike, but a careful observer can pick out subtle differences that others might overlook.

A mixed flock might include several families — warblers, vireos, nuthatches — all moving together in a flurry of activity. Working through a flock patiently can reveal a surprising variety of species.

While I consider late August into September to be ‘warbler season,’ other families deserve attention too. Vireos, for instance, are common in migration. Plumbeous vireos are summer residents from our mixed forests up into the conifer stands of the Bradshaw Mountains and Black Hills. In smaller numbers ou may find the warbler-like warbling vireo and the elusive Bell’s vireo, which normally inhabit the lower desert. Migration can also bring Cassin’s and Hutton’s vireos. Cassin’s closely resemble the plumbeous; they were once considered the same species. During migration it’s possible to see multiple vireo species together, sometimes outside their usual habitats.

Knowing your common birds well is key. If you’re familiar with the plumbeous vireo’s lead-gray tones, you’ll more easily recognize the Cassin’s brighter, chartreuse wash. That familiarity lowers your learning curve when an uncommon species crosses your path.

I would be remiss not to mention hummingbirds. While I think of this as warbler season, many people see it as peak hummingbird season, and for good reason. We can find between five and ten species here in late summer. In higher elevations, Anna’s, black-chinned, rufous and broad-tailed hummingbirds are common. With luck you might spot a calliope, a broad-billed, or something even rarer. 

During spring migration birds are in a hurry northward to claim prime breeding territory, giving birders a narrower window to see them. In fall their pace slows. After breeding they take advantage of the abundant food supply that post-monsoon Arizona often offers (this year notwithstanding). With no urgency to reach their wintering grounds, they move in a slower, more methodical fashion, making uncommon species easier to find.

There’s truly no better time than now. In the closing weeks of August, I recommend heading for elevations between 6,000 and 8,000 feet. While migration can be rewarding in any habitat, I favor pine to mixed-conifer forests this time of year. Go find yourself a Townsend’s warbler, and maybe a few surprises along the way.