Colorful Migrant Warblers Share Special Relationships with Native Plants
Apr 30, 2020 ● By Sheryl DeVore
photo by Stephen D. Bailey
by Sheryl DeVore
Birders both novice or
advanced get downright giddy in May, because that’s the peak time for some 30
species of wood warblers to migrate through the Chicago region. Their names are
descriptive; black-throated green warbler and yellow-rumped warbler, for
example, as well as referential, such as the Nashville warbler, first
discovered in Tennessee. The males are in their stunning breeding plumages now
as they head north to raise a family.
When Maureen Marsh moved
to the Chicago area 10 years ago, she discovered the joys of warbler watching.
“It was the beginning of May at Ryerson Woods [in Riverwoods]. The leaves were
just coming out and when the sun started to hit the top of the trees, I saw a
blue-winged warbler,” says Marsh, who is certified as a University of Illinois
master naturalist. She also serves as secretary for the Lake-Cook Audubon Society and leads warbler walks.
The American redstart is a warbler commonly seen in the Chicago region in mid-May. Photo courtesy U.S. Fish and Wildlife Service.
Marsh says she’s learning
how important warblers are to maintaining healthy oak woods, and that climate
change is affecting the relationship between plants and birds. Warblers are
five-to-six-inch-long insect eaters. Many live in Central and South America in
the winter and are part of a larger group of birds called neotropical migrants.
These birds migrate in spring northward to their breeding grounds. For example,
the yellow-rumped warbler breeds in boreal forests. Some species like the
yellow warbler remain in the Chicago region to breed.
They may be called
warblers, but many of their songs sound nothing like a warbling melody. Some,
like the fairly common black-throated green warbler sings what sounds to some
like a buzzy, “Zoo. Zee. Zoo. Zoo. Zee.”
The most common warbler
seen in the region is the yellow-rumped warbler. On occasion, it remains in
parts of Illinois in winter, but most start coming through in March and April,
with peak numbers in early May. The male has yellow shoulders, crown and rump
contrasting with a blue body, black cheek and white throat. The females, as with
many warbler species, arrive later and appear drabber. A beginning warbler
watcher can see plenty of yellow-rumped warblers in the neighborhood or at a
local forest preserve in late April into mid- to late May, especially along
rivers.
Other common warblers seen
in the region include yellow warbler, black-and-white warbler, which arrive
earlier than other species such as the American redstart, and a
black-and-orange warbler that fans its tail as it searches for food.
Warblers are being studied
nationwide, and scientists are learning ways global climate change is affecting
their relationship with oaks and other trees. “Warblers time their migration to
pass through the region when the oaks are just starting to leaf out,” says
Douglas Stotz, senior conservation ecologist at The Field Museum.
Insects are attracted to
the buds and early leaves, and in turn, warblers are attracted to the insects
for food. When the leaves fully emerge, they contain chemicals that deter
insects. So the warblers have to be there right when the insects are. “With
climate change, plants are leafing out earlier,” Stotz says. Some warblers are
also migrating earlier, but they’re not keeping up with the plants.
“That
has been shown in studies in Wisconsin and some in Illinois,” he says. “It’s a
fairly general pattern. If this happens erratically, it’s not an issue. If it
becomes the standard, then it becomes a huge issue. That’s where we’re headed
if climate change continues.” Stotz notes that this scenario is not only
happening with warblers, but also a host of other migrants that live in the
neotropics in winter.
The yellow-rumped warbler is the most common migrant warbler in the Chicago region and arrives ahead of most of the other warbler species. Photo by Laurel Ahlenius.
Stotz
spends many hours in May searching for warblers at Grant Park, in Chicago, but
plenty of other places in the region also provide habitat for migrating
warblers. “Forest preserves near the Fox, Chicago and Des Plaines rivers are
all corridors through urban environments, and that makes them crucial for
warbler migration,” Stotz says.
Habitat in people’s yards
is an important component for warblers and other migrant birds in the Chicago
area, he adds. “For warblers, the big thing is canopy trees—oaks, hickories,
hackberries.” Maple trees, although native, aren’t as attractive to warblers,
he observes.
Marsh
agrees, advising homeowners should avoid using pesticides that kill the insects
warblers eat. “Warblers are particularly attracted to water,” she says,
recalling the time a prothonotary warbler, with a golden head and body, visited
a water feature in her yard.
Sheryl DeVore has written six books on
science, health and nature. She also writes nature, health and environment
stories for national and regional publications.
Tips and Resources for Warbler Watching
Warblers migrate overnight and often land in neighborhoods in the morning where vegetation signals available food. Here’s how to search for warblers near home, plus some online resources.
- Look for small woodlots with layered vegetation; even a few trees in a backyard will attract migratory warblers.
- Check those areas early in the morning when insects and warblers are active.
- Listen for birdsong and look for small birds flitting in the vegetation.
- Focus on one warbler at a time, noting overall color and whether the bird has wing bars, an eye ring and specific colors on the throat and head. Write notes or sketch the bird to look up later.
- Even
expert birders can have trouble identifying every warbler. Be patient and
enjoy.
Christine Elder’s website offers tips on sketching and identifying warblers, coloring pages for children and online resources for identification.
A Cornell Lab video shows how migrating warblers can be found even in small areas.
For a total immersion in warbler identification, consider an online course.
Identification guides are available at AllAboutBirds.org/guide, Audubon.org/bird-guide, eBird.org and Identify.WhatBird.com
In-Print, Green Living
Climate Change
Green Living in Chicago
Natural Health
Green Living
Bird Watching
birdwatching
Lake-Cook Audubon Society
Habitat
May 2020
Healthy Chicago
black-throated green warbler
Birder
yellow-rumped warbler
wood warbler
Maureen Marsh
master naturalist
The Field Museum
migration
oak
hackberries
maple tree
canopy tree
hickory
Sheryl DeVore
eco friendly lifestyle
