A few weeks ago I was ruminating on my warbler life list, or more accurately the three eastern species missing from the list.
Most of the eastern warblers nest well into the north. For reference, Pictured Rocks National Lakeshore on Lake Superior’s shore has the highest diversity of nesting warblers in the National Park System. So, around this time every year, those of us in the lower Great Lakes region get to see about 30 of the roughly 37 eastern species of warbler as they head “home” to nest for the summer.
The rest of them are often called the 'southeastern warblers.' Hooded Warblers, Louisiana Waterthrushes, and Yellow-throated Warblers are three good examples of this contrarian crew that prefers the steamy southeastern forest to the boreal northwoods to raise their young.
I’d crossed paths with some northern straggler Hoodeds and Louisianas, but the Yellow-throated had eluded me. On a whim, I threw the scope, binoculars, and wife in the car and headed south to Indiana Dunes National Lakeshore. To answer your first question, yes, the wife actually wanted to go, as she’s a birder too. And secondly, yes, Indiana Dunes is actually “the south” when you’re talking about avian biogeography in North America.
Quite a few species of bird that wouldn’t think of venturing up to Wisconsin or Michigan will quite happily settle down just south of those states in the northern reaches of Indiana and Ohio. It’s all related to climate and habitat. Dipping just south of the Great Lakes, you lose the moderating (chilling in summer) effect of the lakes. The result is a different suite of flora with markedly different leaf-out and flowering times. Insects get active quicker and stay active longer.
It’s a different world when you start to look closely. The disparity is never on display better than the last week of April when we drove just a couple hours in a direction that was more west than south, got out of the car, and noticed spring had advanced two weeks. Trillium and trout lilies were at their peak of bloom when their foliage was barely breaking ground back home.
We’d come to the right place. Our first remarkable bird in the park was a Red-headed Woodpecker, normally associated with the Southeast despite having some populations well into the north.
Within a half hour we’d seen seven of these startlingly tri-chromatic woodpeckers in the dry mixed forests near Lake Michigan’s shore. We spied a few more in the Great Marsh area of the park, along with some migrant warblers staging for the next leg of their journey up the long Lake Michigan coastline.
But the warbler I wanted would need an area that was both forested and damp. That we found in a rather obscure unit of this weirdly shaped and somewhat fragmented national lakeshore. It’s called the Heron Rookery unit. You’ll find this heavily wooded area along the Little Calumet River to the south and east of the main park.
It’s not well-marked, or signed, so use a map. A trail follows the river east-to-west across the unit. In the spring this area is guaranteed to produce plenty of bird life and a stunning wildflower show.
One thing that you would expect it to produce, which it does not, is Great Blue Herons – at least not visibly. Supposedly 100 pairs nest in this area, but their “rookery,” such that it is, remains hidden north of the river, on the opposite side of the trail. But we’re not here to see herons, which are readily available in almost every single national park unit in the country.
The slowly meandering water of the Little Calumet is a favorite haunt of the Louisiana Waterthrush. “Waterthrush” is half a misnomer, as they are quite fond of water but are a thrush only in superficial appearance. These skulking birds are truly warblers and a pleasure to find as much as any of the other terrestrial warblers that pose such a challenge to birders.
Another bird in that category is the Hooded Warbler, a striking yellow beauty that prefers bouncing around under the may apples to frolicking the tree canopy. Walking the Heron Rookery trail in late April or May will get you Louisiana Waterthrushes on your north (river) side and Hooded Warblers on your south (forest) side. Right down the middle you have rugged old sycamore trees lining the river. And if there’s one thing that can be said of my target bird for the day, the Yellow-throated Warbler, it’s that they love sycamores.
To find a bird, you find its habitat and study its habits. The sycamores provide the habitat for the warblers to dance along trunks of the larger limbs in the fashion of a nuthatch. More often than not, you’ll find them upside-down, which has earned them the nickname “Nuthatch Warbler” from more than a few birders.
I’d like to recount a harrowing tale of a long, adventurous search for the Yellow-throateds, but the truth is that we heard singing males shortly after setting foot on the trail and ended up identifying at least six males by song and seeing four of them.
We also had the rare pleasure of having a pair descend to a trunk of a leaning tree and copulate right in front of us. Apparently, in addition to loving sycamores and acting like nuthatches, it can be said that Yellow-throated Warblers have no shame.
Thus our trip “down south” to Indiana Dunes was a birding success. Finding the undiscovered gem of the Heron Rookery Trail was an unexpected bonus. And we accomplished it all before mosquito season. That’s a triple win!
Note: Yellow-throated Warblers NEVER quit moving. This makes photographing them an utter impossibility for someone of my meager skills and limited photographic equipment. Hopefully the other warblers are adequate consolation.