Blue-Gray Gnatcatcher by Jackie Bowman |
Invasion of the gnatcatchers
(published 9-5-17)
There is a tiny gray and white bird with a longish tail that
you might know. If you don’t, it’s probably just a matter of time.
I’m referring to the blue-gray gnatcatcher, an avian sprite nicknamed
the “twig fairy” by birding guru Pete Dunne for its dance-like foraging
technique.
For pure energy, the gnatcatcher has few rivals. The bird seems
to be in constant motion, making it easy to detect but challenging to follow
with binoculars.
Gnatcatchers are quite vocal, and once you learn its wheezy,
high-pitched voice you’ll realize this bird is surprisingly common in
neighborhoods and forest preserves alike. In fact, finding one in DuPage County
has never been easier.
This wasn’t always the case. One of my birding friends
recently referred to the blue-gray gnatcatcher as the “poster bird for range
expansion.” Translation: it’s a traditionally southern species that has spread
across the Great Lakes region in a big way.
“Their breeding range has moved north by about 200 miles
over the last 25 years or so,” said Doug Stotz, senior conservation ecologist at
Chicago’s Field Museum. “I actually think that blue-gray gnatcatcher may be a
climate change winner.”
The numbers don’t lie. I looked at Spring Bird Count records for
DuPage County since 1975, the first year of data collection. Zero gnatcatchers
were found in 1975-1978, and less than 10 were spotted in the years 1979 to
1983. But sightings picked up in the late 1980s and hit triple figures for the
first time in 1996 when 104 gnatcatchers were seen.
Spring Count totals in 11 of the last 14 years have been 300
or more, with a high of 550 in 2014. Bird Conservation Network data for the
Chicago region also indicate a population boom.
I’ve noticed the upward trend in my own Glen Ellyn backyard.
I went seven years before seeing my first blue-gray gnatcatcher at home, in
2004. I was thrilled! Little did I know how common this experience would soon
become.
This summer, in fact, the presence of gnatcatchers was so consistent
that I’m convinced a pair nested close by.
So, what’s going on? Stotz has a few theories. Because
blue-gray gnatcatchers are insectivorous and winter widely in the Southeast
U.S., he said, milder winters may be proving advantageous to the species.
“Beside this, I suspect that restoration of oak woodlands
helps them in the Chicago area,” Stotz said. “They like oaks and they like
things pretty open.”
The subject of range expansion recalls a few other species
that are creeping northward with greater frequency. Yellow-throated warbler,
summer tanager, Carolina wren and northern mockingbird are examples of
“southern” birds that now breed in the Chicago region. But none approach the expansion
success of the blue-gray gnatcatcher.
Identifying this bird is easy. I mentioned the gnatcatcher’s
wheezy call, which stays in your head once you know it. Visually, the bird’s
obvious field marks are a blackish tail with white edges (like a junco) and a
conspicuous white eye-ring.
The hyperactive motions of the blue-gray gnatcatcher can
clinch the ID, too. Its relatively long tail flicks from side to side when the
bird is foraging in trees, likely a strategy to scare up small insects. Sometimes
it momentarily hovers.
Gnatcatchers will be with us a few more weeks before
starting their southerly migration. Some will travel to Mexico and Central
America; many stop in Florida, where the species is resident throughout the
year.
Next April, the twig fairy will return, bringing with it
enough nervous energy to impress even the kinglets. If you ever wondered what a
cup of Starbucks might do for a bird, watch and listen for the blue-gray
gnatcatcher, a migrant on a mission.
Copyright 2017 by Jeff Reiter. All rights reserved.