Marvelous May Migration

photo of a bird, a mountain bluebird on a dead branch tip
Mountain Bluebird (c) Mike Anderson Macaulay

As I look toward having more time to get out birding, an annual dilemma emerges at this time of year ― where in the world should I bird in May! Across the Northern Hemisphere, this spring month offers some of the most exciting opportunities of the birding year. Here in Colorado, especially on the eastern plains, we can catch a great variety of species heading from their southern wintering grounds to breeding areas in the Great Plains, boreal forest, or Arctic tundra. Although many waterfowl and raptors have already departed our state, May provides a smorgasbord of regular and occasional migrants. May is also the time when many breeding birds return and begin building nests and laying eggs. By getting out in early May, you can start re-acquainting yourself with the songs of our local breeders so by the time the migrant songbirds arrive in mid-to-late May, you will be able to pick out the singers you don’t recognize.

Spotted sandpiper – juvenile
(c) Mick Thompson

Of the 43 species of shorebirds recorded in Colorado, 25 (58%) are regular migrants through the state, and 12 remain here to breed. North Park is a great place to look for breeding and migrant shorebirds in the spring. At the end of April, I led a field trip to the Lower Latham Reservoir area (east of Greeley), where we tallied 12 species of shorebirds; not bad, but species diversity will increase in May. Heading there at the end of May might produce one of the rarer migrants, the White-rumped Sandpiper, which nests in the high Arctic of Canada.

Virginia’s Warbler (c) Bill Schmoker

Nothing signals the start of the flowering season more than the appearance of colorful wood-warblers. Forty-seven species of wood warblers have been recorded in Colorado, but only 10 might be considered common breeding species. Warbler migrants are a mix of boreal species heading north and eastern species on the far western edge of their migration range. Locally, we have recorded 32 warbler species in the Bear Creek Watershed. Heading down the hill will likely be more productive than staying high in the mountains. Cottonwoods along the Platte River and in isolated groves on the plains are choice spots for warblers and other songbird migrants. Vireos, flycatchers, and thrushes migrate through Colorado in May, some not until the very end of the month.

Cornell Laboratory of Ornithology and their partners have developed a tool, BirdCast, to help plan your days afield. Here you can get a continental overview of migration potential or hone in on a specific city (use the “Migration Tools” tab). I hope this May can be one full of great birding memories.