Admittedly, the spring migration of warblers along the Front Range urban corridor is far less spectacular than it is in the Eastern U.S. where their numbers and variety are much greater. Nevertheless, regional birders look forward to the arrival of these colorful spring migrants and summer residents, an annual event that stretches from mid March to June and generally peaks in early-mid May.
Indeed, for the past month, isolated sightings of yellow-rumped warblers have been reported in the region and, over the past week or so, the first common yellowthroats have appeared. This morning, at South Platte Park, I encountered thirteen yellow-rumped warblers (in two flocks), indicating that their migration is beginning to accelerate; last year, on May 3, I was treated to an invasion of these cold-loving warblers, when an estimated 300 filled the trees of the Park. Yellow warblers, the most common summer warbler along the urban corridor, should begin to arrive in a week or two and will be nesting by late spring. Wilson's warblers, which nest near timberline, are often abundant near area lakes in early May; other fairly common migrants along the urban corridor include Tennessee, Nashville, Black and White and Townsend's warblers, northern parulas, American redstarts and northern waterthrushes. Summer residents on the Piedmont include yellow warblers, yellow-breasted chats and common yellowthroats; Virginia's warblers, ovenbirds, orange-crowned warblers and chestnut-sided warblers summer in the foothills while MacGillivray's and Wilson's warblers head for the higher mountain forests.
One need not visit State Parks or nature preserves to observe the spring parade of warblers since many turn up in suburban yards and urban parks. Patience, a decent pair of binoculars and a good field guide are the primary requirements for those hoping to observe and identify these small, active insectivores.