By: Jeanne Henderson
When you’re walking around most marshes in the Saginaw Bay area, listen for the clear song of a nearby bird singing “sweet, sweet, sweet, oh so sweet!” Follow the sound as it moves through tangled branches and soon a flash of yellow appears in an opening. This tiny songster is a male yellow warbler, with a bright yellow body and chestnut-colored streaks on its breast. Having migrated thousands of miles from southern Mexico or Central America, yellow warblers complete their journey to their breeding habitats in the northern United States and Canada.
Look for yellow warblers in thickets of willow and alder near ponds, marshes, rivers or other wetlands. Males will sing while sitting on the outer branches of shrubs or trees such as cottonwood and maple, often bobbing their tail up and down slowly. A male sings to attract a female and claim his territory from similar suitors. Males arrive here in late April through early May, ahead of females, delighting bird watchers who look forward to spring migration. Males wear colorful patterned plumage, while their female counterparts sport plain yellow, a characteristic known as sexual dimorphism.
Watch warblers feeding as they flit between branches, gleaning insects and spiders by picking them up with their sharp, tiny bill. They may hover briefly next to leaves to find caterpillars, a favorite food.
After mating, the female builds a nest on an upright forked branch of willow, dogwood, honeysuckle or hawthorn, about 3 to 6 feet high. She constructs a deep cup of grasses, plant fibers and strips of bark. The exterior takes on a cotton-like appearance from the soft white fluff of cattail, cottonwood or dandelion. Some nests may contain deer hair or rabbit fur. The female incubates four or five eggs for 11 to 13 days, while the male brings her food.
Brown-headed cowbirds parasitize many warblers by laying their eggs in the warbler nests, forcing warblers to raise the cowbird chicks. This results in reduced survival of juvenile warblers as the larger cowbird outcompetes for food. However, the female yellow warbler responds to the intruder by adding another layer of materials over the cowbird egg (and her own eggs), then laying again; this may happen up to four times. Or, she may abandon the nest and restart in a new location.
Look for warblers and many other species during spring migration!
Flights of Fancy
May is the peak month for bird migrations. Every day, new species arrive to rest and refuel before continuing on their journey north. During migration, they mix and travel together as waves of birds “fall out” (land) in the morning after flying all night. Good places to look for warblers in the Saginaw Bay area are Bay City State Park, the Joseph M. Soehnel birding trail in Hampton Township, Chippewa Nature Center in Midland and Green Point Nature Center in Saginaw.
Tiny, active birds with brightly colored plumages, warblers dart around tree branches, sometimes at high levels, making it hard to distinguish their field marks. Some hide and skulk low in dense thickets, while others will disappear into coniferous branches. Yes, they are challenging, but birders enjoy the opportunity to see, hear and identify the 30-plus warbler species.
Many warblers choose to stay in Michigan, breeding in a variety of habitats throughout summer. Beside the relatively abundant yellow warbler, you can find ovenbird, common yellowthroat, American redstart, yellow-rumped warbler and pine warbler.
You can help all migrating birds by preventing window collisions, providing fresh water in birdbaths, keeping cats indoors, turning off outdoor lights at night, growing native plants and reducing use of pesticides.