May Nature Notes

Colorful warblers and woodland wildflowers make May a good time to enjoy the outdoors in Minnesota. The singing birds and numerous flowers seemingly proclaim spring.

Birds that do not overwinter in the state actually begin returning much earlier. Waterfowl can arrive as soon as there is open water, and shorebirds begin arriving in April. But wood warblers, songbirds that are emblematic of spring, typically don’t arrive in numbers until mid-May. Many are neotropical migrants, returning from a winter spent in South and Central America. Most are boldly colored, some with bright yellow breasts, black “necklaces” or masks contrasting with areas of red, green or blue on their heads and backs. Small, active and colorful, they are the “butterflies of the bird world.”

Encountering a flock of warblers is a memorable springtime experience. Trees once quiet suddenly come alive—filled with the movements of small colorful birds flitting from branch to branch, hunting their insect prey. Bird watchers sometimes complain about getting “warbler neck” from craning to see the birds moving about overhead, darting behind leaves and offering only a glimpse of their dazzling colors.

A warbler flock can include many kinds—there are 54 species of warblers in North America and many of those come to Minnesota to nest in the state’s forests, notably in the Northwoods and bogs. Yellow-rumped warblers are among the most numerous, arriving early and staying late, sometimes even overwintering. Blackburnian warblers are hard to find high in the tops of trees; experienced bird watchers often locate them by hearing their song and then looking for the singer. American redstarts flash black and red as they fly out from a branch to grab an insect on the wing. Many other warblers carefully and methodically glean insects off bark and leaves; black-and-white warblers even crawl nuthatch-like along the trunks of trees. Some warblers spend much time on the ground: ovenbirds and palm warblers can be seen looking for insects in the leaf litter. 

Complementing the colorful warblers above are the numerous springtime ephemeral wildflowers below on the forest floor. These plants are “ephemeral” because their growing season is short; they appear, flower, then disappear (remaining dormant underground until the next spring) in just a few weeks—some plants may be in flower for only a few days. In this way, they take advantage of that brief window of time when direct sunlight can reach the forest floor before trees leaf out. There are exceptions: hepatica’s leaves stay green long after its flowers have faded, and wild ginger (not related to the spice) can remain green through much of the summer—it is often planted as a ground cover in woodland gardens.

An online index reveals the many wildflowers blooming during May in Minnesota. Wood anemones can cover large patches of ground; bellwort grows often in isolated stands, its tall stalks almost hiding its hanging yellow flowers; and Dutchman’s breeches has oddly shaped flowers that resemble pants hanging on a line to dry. Bloodroot is so-named because its “sap” is red. Bloodroot is one of the many woodland wildflowers whose seeds are dispersed by ants, a process called myrmecochory—a fatty body on the seed called an elaiosome attracts ants that carry seeds away and bury them in their nests.    

There are many places to see both wildflowers and warblers in Minnesota. An excellent resource for learning about wildflowers is the Eloise Butler Wildflower Garden in Minneapolis; woodland, wetland and prairie plantings there provide flowers to see throughout the entire growing season. Big Woods remnants are good locations for seeing both flowers and birds at state parks such as Nerstrand Big Woods, Lake Maria, or Forestville/Mystery Cave. Frontenac State Park, on the shoreline of Lake Pepin, is renowned among bird watchers as a “hot spot” for seeing migrating spring warblers.