Fieldwork: Hermit Thrushes and Invasive Weeds

Tuesday, June 14th, 2016


Spreading phlox, Phlox multiflora, blooming in the clearing where I work in the morning.


I spent the morning squatting in a clearing atop a small ridge just off the Upper Terrace Road at Mammoth Hot Springs in the northern edge of Yellowstone National Park, hand-digging russian knapweed (Acroptilon repens) shoots. A Hermit Thrush serenaded me as I worked, its fluting song echoing through the nearby grove of Douglas-fir trees. 


After two and a half hours of steady digging and pulling, my lower back ached from the strain, and my quads burned. A rainstorm blew in, spitting hail, and I decided to take a break. 


As I stowed my digging tool, water bottle, and bear spray in my day pack, and scrambled down the ridge in the pelting rain, I remembered the Hermit Thrush's song and smiled. That thrush is part of why I am spending two weeks volunteering to grub out invasive perennial weeds in the landscape that I have loved ever since I can remember. 


What does knapweed have to do with Hermit Thrushes? It crowds out native plants, killing them with a natural herbicide exuded by its rhizomes and roots, and it doesn't provide habitat for native insects. 


As entomologist Douglas Tallamy puts it, "a plant that isn't feeding insects isn't doing its job." Hermit Thrushes and other songbirds raise their young on insect larvae. A lot of larvae: Tallamy's studies show a pair of chickadees feeds 6,000 to 9,000 insect larvae to raise a single brood! 



Arrowleaf balsamroot (Balsamorrhiza sagittata)


So an infestation of thousands of Russian knapweed plants crowding out the native spreading phlox (the sweet white-flowering Phlox multiflora in the photo at the top of the post), yarrow, fleabane, arrowleaf balsamroot, and other wildflowers means no insects, and thus no food for nesting songbirds. That's just one example of how invasive weeds disrupt and degrade the webs of relationships that create healthy natural ecosystems. 


Crowding out the wildflowers of course also means less food for the hundreds of species of native bees and butterflies, plus hummingbirds and other pollinators. And it changes the soil ecosystem as well, which may mean the soil becomes less fertile altogether. 


And of course, plant communities altered by invasive weeds directly affect the lives of the "large charismatic wildlife" that attract millions of visitors to Yellowstone every summer. Like the cow elk in the photo below, who was grazing placidly in the Mammoth Campground just yards from Space 50, my home for the term of my time here. 



The other perennial invasive I'm working on eradicating while I'm here, houndstongue (Cynoglossum officianale), a robust plant that looks something like comfrey but with deep purple flowers, is poisonous to grazers, including elk. The plant fills its tissues with anti-grazing compounds that stop liver cells from reproducing, causing grazers to slowly die of liver failure. 


I've been digging knapweed in the morning, and then switching to the much larger houndstongue in the afternoon to vary the work--and to give me a mental break. I grubbed out a whole trash bag of houndstongue today before heading to Gardiner, Montana, just outside the park, for lunch and internet access (as well as electricity to charge my laptop). 


And now it's time to head back to houndstongue eradication before I wear out for the day. I'm working hard, but don't feel sorry for me. I'm happy doing work that helps heal the landscape that is the home of my heart. 



The view from my houndstongue eradication project "office" this afternoon.


My muscles may be sore by the end of the day, but my spirit is singing.