Sweet, Sweet, I’m So Sweet!
The Great Outdoors | May 31, 2017
By Jackie Scharfenberg, Wisconsin Department of Natural Resources
“Sweet, sweet, I’m so sweet!” Whistle it loud from a high perch. “Sweet, sweet, I’m so sweet!” Whistle it in less than one second and repeat ten times per minute or 3,200 each day! Don your brightest yellow outfit with reddish streaks along your chest and give yourself a large black eye! Congratulations, you can now claim membership into the yellow warbler (Setophaga petechia) clan!
That’s well and good for the males, but the females sport a more subdued yellowish coloration. She still possesses large black eyes and speaks in chips, like her male counterpart. When in flight, both flash yellow patches on a dusky gray tail. These small birds measure about five inches in length with a six to eight inch wing span. They weigh in at a “whopping” .3 to .4 ounces (less than two quarters)!
Habitat and Migration
The tiny dynamos breed from the Arctic Circle into Mexico. They spend the winters, mainly in mangrove forests, from Central America into the northern half of South America. Listen and then look for them in willows, thickets, shrubs (especially along lakes and rivers) or in wetlands. They arrive in Wisconsin in early May and return south by late July or early August.
Nesting and Young
While the male defends the territory by singing and sometimes performing a fluttering- flight display, the female selects an upright fork of branches in a shrub, small tree, or briar bush to build her compact, open cup nest. She constructs her nest with plant stalks, shredded bark and grasses and lines it with plant down and fur. She lays three to six greenish-white eggs speckled with brown, olive, or gray spots. The male feeds her while she incubates the eggs for 11 to 14 days. Both parents feed the young until they leave the nest in nine to 12 days becoming completely independent at about three to four weeks old.
Diet
Yellow warblers forage energetically with quick hops along thin branches and twigs. Using their tweezers-like bills, they glean insects from the leaves and branches. Sometimes, they hover briefly to grab a tasty morsel from the underside of a leaf. Two-thirds of their diet consists of juicy caterpillars. They also eat mayflies, moths, mosquitoes, beetles, treehoppers, and other insects. Occasionally they will dine on spiders and some berries.
Interesting Fact
Brown-headed cowbirds do not build a nest or raise their own young so they lay their eggs in other birds’ nests – including about 40 percent of yellow warbler nests. Many times, a female yellow warbler detects the larger cowbird egg and builds a new floor over the eggs and then lays another clutch of her own. Researchers once found a yellow warbler nest with six floors! If a cowbird egg hatches, the bigger cowbird often out-competes the smaller warbler nestlings for the food brought to the nest by the over-worked yellow warbler parents. Nestlings also face predation by snakes, jays, and climbing rodents.
Photo by Charlesjsharp
