Skulky, scarce and secretive, Connecticut Warblers are famously elusive

Research on Canadian breeding grounds provides insight into a little-understood bird

Connecticut Warblers are famously elusive and secretive birds. Even at Montrose Point, where hundreds of warblers were found this weekend, there were just two reports of Connecticut Warbler.

“In general, they are very hard to find,” says Emily McKinnon of the University of Manitoba. “They seem to always be in really dense habitat. They are one of those birds that is really not obvious in migration.”

But Connecticut Warblers are moving through Chicagoland in some numbers, and a handful nest as close as northern Wisconsin and the Upper Peninsula of Michigan. McKinnon has unique insight having studied Connecticuts on their breeding grounds in the boreal forest outside Winnipeg. And Connecticuts, like other warbler species, are very little-studied.

“I think the surprising thing at their breeding sites is that they are so obvious,” McKinnon says. “They’re very different personalities on their breeding sites.”

Connecticut Warblers, though, have declined in numbers like so many migratory songbirds. A paper just released last month states that the birds have declined by 62% on the breeding grounds since 1966.

McKinnon and her colleagues have attached light-sensitive geolocators to the warblers to understand their migratory routes. That scarceness in spring migration that we experience in Chicago is part of the story. Some Connecticut Warblers in fall migrate east and south over the Atlantic Ocean to get to their wintering grounds in South America’s Gran Chaco region. Others migrate through the interior of North America.

The new paper found that habitat loss and fragmentation on the breeding grounds “are strongly correlated with population declines.” Among the challenges facing Connecticuts are conversion of forest to agriculture and peat mining. Not to mention the typical suite of challenges such as building collisions that face so many of our birds.

“Connecticuts do have to go through this gauntlet of the Great Lakes area,” McKinnon says. “They funnel through Chicago, Detroit and Toronto…a window strike is a bigger negative impact because there’s less of them.”

And while elusive, those few sightings in Chicago do make a difference, as do local habitat restoration efforts.

“They’re not a very abundant species to begin with,” McKinnon says, “so conserving stopover habitat would be disproportionately important.”

Like Connecticut Warblers, Prothonotary Warblers are another migrant songbird that needs some help.

I shared with paid subscribers on Friday the uncanny experience I had with Prothonotary Warblers in Central Illinois. I traveled to Springfield for my second Moderna shot and met up with Jarod Hitchings at a nearby natural area to learn about the nesting boxes he’s installing for Prothonotaries. I left without seeing one, though, only to encounter one very unexpectedly a few hours later.

On Thursday, May 27, I’ll be sipping bourbon and talking swamp warblers with Jarod from 5-5:45 p.m. We’ll learn about his efforts to make and hang 273 nesting boxes for these golden birds of Illinois bottomlands. Register for this casual This Week in Birding conversation on Zoom below.


TWiB Notes

It’s that time of year again when we have fledglings. The above image from a group in New York City summarizes things well. If you encounter a downy little one, leave it be!…..The Interior Department has taken steps to revoke a Trump-era rule that weakened the Migratory Bird Treaty Act, which protects birds from “incidental take.” The National Audubon Society called the move a “critical step.”…..Locally, though, birds in Indiana will face new challenges due to a state law that repeals protections for the state’s wetlands. Audubon Great Lakes suggests contacting Indiana lawmakers about the bill.

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