Cooperative Living July 2019 - 36

FeatheredFriends | Story and artwork by Carl " Spike " Knuth, Contributing Columnist
Warbling Vireo
F
or many years, it was my
mystery bird. As a boy of
11 or 12, I would hear them
singing in the tops of large
deciduous trees along the shores
of Wisconsin's Okauchee Lake
35 miles west of Milwaukee. The
birds would sing their warbling
song constantly, even in the heat
of an August afternoon high up in
the trees. Now and then, I caught
a glimpse of one or two but only
as silhouettes or shadows in the
dense upper canopies of maples,
oaks, willows or cottonwoods. I
had no binoculars so I was never
able to see colors to identify them.
As time went on and I studied my
bird identification guides, I finally
realized through the habit and
habitat information that I was
seeing warbling vireos. I heard
that familiar song again years later
at the Virginia Department of
Game and Inland Fishery's
Brookneal striped bass hatchery
along the Staunton River. That
time, I had binoculars and was
able to finally see the bird and
its colors.
The warbling vireo is difficult to
identify, being very plain with no
outstanding field marks. The word
vireo is Latin meaning " I am
green, " and one of its old names is
warbling greenlet. Vireos are
closely related to shrikes, having a
similar small hook on their bill.
However, they don't prey on small
birds and mice like shrikes. They
are the palest of all vireos.
Measuring about 5½ inches, the
upper parts are greenish-gray or
olive-gray with a faint olive-green
crown and faint eyebrow and pale
lores in front of a dark eye. The
34 | Cooperative Living | July 2019
Their song can be described as a clear warbling with
many notes running together in a long melodic warble.
bird's whitish breast has a yellowish
tinge on the sides and flanks, but no
wing bars or eye rings. This is
another bird that is seldom seen, let
alone identified, but can be heard
due to its persistent singing. The
song can be described as a clear
warbling with many notes running
together in a long melodic warble.
Legendary ornithologist A.C. Bent
wrote that it has " an air of unhurried
calm, a 'leisureness' we seldom
hear in the voice of a bird. " Some
studies claim it may repeat its song
4,000 times a day. Its warble has
been likened to the purple finch
but longer.
Male warbling vireos tend to
arrive first from Central America and
Mexico around mid-April and begin
claiming their territory immediately.
After a courtship ritual of weaving
their bodies side to side with
quivering wings and bill clashing,
the female seeks out a nesting site.
Usually it is high in the tops of
deciduous trees on a slender
horizontal branch although, on
occasion, low to the ground. She
forms a cup-like hanging basket
affair, suspended from a fork. It's
made of plant down, leaves, grasses,
animal hair or fur, spider silk,
cocoons, paper or string. Three to
five eggs are laid; white, spotted with
dark or reddish browns. Incubation
takes 12-14 days. The young are
naked with dark yellow skin and
tufts of light brown down. Once
hatched, both sexes participate in
feeding them. A parent bird is always
at the nest or nearby, and can get
quite aggressive toward interlopers.
However, warbling vireos do fall
victim to cowbird females dumping
their eggs in the vireos' nests. The
young fledge in about 13-14 days
and will feed with the adults for a
time. There may be a second brood.
Warbling vireos favor open
woodland habitats in stands of
tall deciduous trees such as
cottonwoods, willows and
sycamores, especially in river
bottoms. They also like the edges of
woodland clearings, open groves,
orchards and other tall trees, such as
elms, lindens, oaks and maples in
hedgerows in between fields along
lake shores, roads and even
suburban and small-town streets.
Here they will move slowly, almost
crawling through the leafy crowns
of the trees feeding mainly on
caterpillars of moths and
butterflies, and other insect larvae
such as beetles, ants, wasps, flies
and spiders. They forage slowly and
deliberately stalking prey or
sometimes will hover or fly out at it
like a flycatcher for flying insects.
Larger caterpillars are hammered on
a branch to subdue them. Towards
the end of summer, they'll utilize
wild berries such as elderberry,
poison ivy or oak and others. While
seldom seen, warbling vireos are
common and numerous and studies
indicate that they are actually
increasing in numbers.
For a while, not much was
known where they went in winter.
But more recent information
indicates that they will leave us
starting in September. By late
September and early October, they
make their ways to Mexico, El
Salvador, Honduras, Guatemala and
other adjacent parts of Central
America and parts of South
America, often in mountains at
2,500 to 4,000 feet elevations. 
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Cooperative Living July 2019

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