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Meet the Mint Humbug

Tuesday, August 31, 2021

Pssst. Fall migration is in full swing. While you're asleep, warblers by the hundreds and thousands are slipping through the treetops, silently making their way toward Central America. Getting out before the frost comes, giving themselves plenty of time to travel in night skies, dropping down to forage in insect-laden leaves at daybreak. It's Fat City out there, the best time to travel, when caterpillars and crickets and spiders and aphids are everywhere. 

When there are redstarts on the roof, the move is on. You hear their lisping calls in the sky each morning. Watch the trees, see them cartwheeling through.

This little immature female black and white warbler has eaten her share of spiders, I am certain. She's clinging to the trunk of a golden Chamaecyparis right outside my studio window. If she recalls a nuthatch in her stance, that's no accident. This is the warbler who lives like a nuthatch.

She sticks close to the trunk of the tree, peering at the bark and limbs for anything crawling there. Her Latin name: Mniotilta varia, means "varied (striped) moss-plucker." Mniotilta is a monotypic genus, meaning there's only one species in it--this one. Though this bird mostly specializes on bark, it will often glean foliage. All birds are opportunists.

In this way, warblers carve up the habitat, each taking its niche within the same forest. If I remember anything from my ecology courses in college, I remember being taught to see forest birds, especially warblers, as a guild, with each one specializing in combing different parts of the tree. This is how Nature packs the forest with so many birds. If they all foraged the same way, there wouldn't be room for them all. So some take the crowns, some the shrubbery; some forage on the tops of the leaves, and some the bottoms. 

Black and white warblers spend a lot of time hanging head-down and hitching around on the bark and limbs. As such, they have strong legs and large feet.

The hallux, or hind toe, is particularly long and robust, with a large hooked claw from which the bird can hang. Much like a nuthatch's foot. Isn't that cool? From Birds of the World account by John Kricher: 

Mniotilta is treated as monotypic because of morphological adaptations for vertical (tree trunk) foraging (Parkes 1978), adaptations that include an elongated hallux, roughly as long as the tarsus (Ridgway 1902). 

Translated, that means that the hind toe of this bird is nearly as long as its leg! Check out that feature on this white-breasted nuthatch, also shot from my studio window:

Isn't it neat to see the congruencies of behavior, coloration and structure in these two unrelated species, based on the similarity in how they make their living? Convergent evolution, y'all. It makes the world go around.

Disruptive coloration, black and white striations resembling tree bark, help break up the bird's form as it works the bark. Even the undertail coverts are spotted. I noticed that this young female's nails are a fetching golden color. Now I want to check every black and white warbler to see if that color stays into adulthood. Look at those golden grappling hooks! 

From my friend John Kricher's account in Birds of the World (formerly Birds of North America), I learned that the "distal toepads (are) usually notched, a possible adaptation for bark foraging (Clark 1973b)" Blowing up my photo, I see a teeny weeny notch just anterior to the fattest part of the big toe pad. Do you?

Nice to have a black-and-white warbler so close that you can grab a photo of the notches in its distal toepads!

The black-and-white warbler is famous as a vagrant, showing up somewhat regularly in fall in Britain and Ireland. You can imagine how that thrills European birders, who are accustomed to waxing poetic about the drabbest of their hopelessly drab warblers. When you've been rhapsodizing about birds that look like this...

Great Reed Warbler, Wikipedia Commons. A lovely bird, but no Mint Humbug.

...imagine THIS striped beauty showing up, knocking everyone's damp woolen socks off.

Ah, Facebook. Beneath one photo I posted there, I got this comment from Megan Crewe, a bird tour leader for Field Guides, Inc: 

"Did you know that the British birders' nickname for these little sprites is "Mint Humbug"? That's a black-and-white peppermint candy here."

                                      Naturally, I had to check and see why...Waah hahaha!!!

Leave it to the British to come up with such a perfectly droll name for our gorgeous warbler. Mint Humbug. I can see them, whispering in code, so the rarity-seeking throng can't hear. "Psst. Mint Humbug, working a large beech, corner of Gloucester and Wembly, still there as of 1400 hours Tuesday." Thank you for that smile, Megan!!

I am delighted to say that these little darlings breed in my southeast Ohio forest. In the spring of 2020, rainy, cold and wet as it was, I watched a pair constructing a nest in the newly-cleared farthest reach, among the black maples. They were tucking wads of bark-fluff and moss at the base of tree trunk. What a weird place for a warbler nest, but then black-and-white warblers are among the weirdest of warblers. Ground nesters--with all these chipmunks and snakes and raccoons...arrrgh. Yet somehow they persist.  I never knew if the 2020 nest was successful; I was not about to walk up to it and lead predators there. Plus, I was too busy feeding starving migrants and bluebirds that awful, freezing cold, rainy May. The black-and-whites were back in 2021, voicing their squeaky-wheel song in the tulip grove just off the lower path in the orchard,  and though I rarely caught so much as a glimpse of them, that squeaky song made me smile so big. Knowing they were there was everything.

I'd love to think this little gal was hatched here, but in the fall, one never knows. The black-and-whites and all the other warblers are streaming through now. Go out, willya, and catch the show. 

Recommended Citation

 Kricher, J. C. (2020). Black-and-white Warbler (Mniotilta varia), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.



When I saw your teaser photo of the halluces on Facebook, my newly awakened brain was thinking, Wait a minute, what is that and how is it articulated? It's a bit embarrassing to say how long it took me to realize I was looking at the back end of a bird.

Around here I see very few warblers, mostly because they always seem to be way up in the canopy and if they're down low, they are obscured by the foliage.

Thanks for the glimpse!

So timely for us--Pam and I watched a
Mint Humbug" poking around on our deck railing this morning, investigating Pam's flower boxes, and then flying up onto a larch snag that we "planted" in the backyard for just such bark-gleaning specialists as the Black-and-white Warbler! Great post, as always!!

Mint Humbug. Will stick with me now every time I see one. Like Yellow Rump Warblers that are Butter Butts

I was so in the mood for this post. Fascinating. And I my have remembered more in college biology and beyond had I been taught in similes and metaphors. I'll remember the guild concept. Thank you for this post. Pure joy. Kim in PA

So interesting! Thank you!

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