Forest Explorations

August in the Fells

Summer is beginning to wind down in the Fells. This season has been especially dry; premature, still-green acorns litter the ground around us and the vernal pools we pass are parched. Still, there is no shortage of interesting natural phenomena to explore. Our group moves at a leisurely pace, delighting in flora and fauna of all sorts, from the smallest leaf miner to the expansive communication network between trees and fungi mycelia.

About the Author: Mina Burton ➔

“Seeing the Fells through a naturalistic lens instead of a purely recreational one fundamentally changed my perception of the space. I began to pay attention to places differently, noting not only individual species but also the relationships between these species and their environments and interspecies interactions. Observing and recording these kinds of details over time can show us the effects of climate change on biodiversity and inform how we protect that biodiversity.”

Mina’s interest in natural history took root during a New England field studies course at Lesley. This course involved learning about ecology and plant identification at local parks and urban wilds. One of these sites was the Middlesex Fells...

Once a month, Claire and Kathy lead a biodiversity walk in the Fells. It’s a free form activity of ours which the only purpose is to explore what Nature wonders are in season: what is flowering, fruiting, passing by, living here?

We invite our guests to write about the walk. Here are highlights of what Mina and we enjoyed this time!


This Saturday’s Forest Exploration was very well-attended, bringing with it new faces and a great sense of wonder and enthusiasm. Every month EwA leads these biodiversity walks to encourage people of all ages and walks of life to explore the Fells as it changes throughout the seasons. This weekend was the first Forest Exploration that we have reopened to the public. We were fortunate to have Larry Millman and Peter Alden joining us, as both are experts in their respective fields of mycology and birding.


A Tough Year for Squirrels

Many of us at EwA have noted how dry this season has been. As our group entered the Fells, we quickly noticed numerous fallen acorns that had dropped prematurely. Trees have cut short their acorn production due to stress and to conserve energy, leaving squirrels struggling to find enough food.

This hardship is exacerbated by the fact that last year was a mega-mast year. A mega-mast is an evolutionary adaptation where many trees drop their fruit simultaneously to ensure that at least some fruit survive to adulthood. The additional acorns provided by an oak mega-mast leads to a boom in the squirrel population. The heightened squirrel population from last year in conjunction with this year’s premature acorn drop does not bode well for this year’s squirrels.


A Rare Find

As we made our way up the trail from the parking lot, Larry Millman pointed out a black fungus nestled in the bark indentations of a fallen log. What he initially identified as Black Witches Butter turned out to be Black Bulgar (Bulgaria inquinans). Only two other observations of Black Bulgar have been made in the Fells, and only a handful have been observed on iNaturalist in the state of Massachusetts. 


Life Within a Leaf

Leaf miners are small and often overlooked creatures that live within the upper and lower surfaces of a leaf. Before my internship with EwA, I had never paused to examine the small insect tracks found on the leaves of many plant species.

Leaf miners may include fly, moth, and other insect larvae. Many leaf miner species have specific plant preferences. The leaf miner tracks that we spotted were etched into a wild sarsaparilla leaf. In the photo on the left below you can see clearly how the tracks get larger as the leaf miner grows. This pattern serves as an indication of the size and age of the leaf miner. The miner on the right was sighted a few days later on a Rose species and is likely to be the doing of a Pygmy Eye-capped Moth.


Dry PoolsToo Dry Even?

During our walk, we passed one definitive vernal pool and several possible ones. At EwA, we work to certify vernal pools at the Fells. To do so, we must first prove that they contain certain species such as wood frog tadpoles or fairy shrimp. Vernal pools are important habitats for amphibians, 40% of which are endangered worldwide. We are concerned that the current drought may have rendered the vernal pools extremely dry and potentially uninhabitable for the amphibians that would normally rest, den, and breed there.


Bird Life on the Edge

Situated at the edge of the vernal pool was a stand of trees sporting horizontal scarring. Peter pointed out that these markings are the handiwork of Yellow-bellied sapsuckers (Sphyrapicus varius). These birds peck at trees to release a syrup which then attracts insects that the birds can eat.  

Larry brought up another interesting detail regarding relationships between birds and trees. Cavity birds such as chickadees take stock of bracket fungi, or polypores, that grow on surrounding trees. The existence of Bracket fungi indicates to the bird that the tree is weaker and easier to dig into, thus making it a more appealing candidate for cavity nesters. 


Fungi Foray

During dry seasons, fungal parasites go into overdrive mode. Mushrooms are somewhat immunocompromised in dry conditions, making them easier targets for parasites. On our walk, we discovered a Hypomyces parasite on a bolete mushroom. The mushroom was nearly rock hard to the touch due to the lack of rainfall this summer. Larry remarked on the ongoing “disagreement” between mushrooms and lichens; while mushrooms favor wetter conditions, lichens prefer dry environments. 

As we made our way deeper into the forest, we soon came across two species of mushrooms that are often confused, thus earning them the names “Turkey-Tail” (Trametes versicolor) and “False Turkey-Tail” (Stereum ostrea). I had seen both before but had never learned to distinguish between the two. The key to differentiating between Turkey-Tail and False Turkey-Tail is that the latter has a smooth underside void of any pores or gills. One tip for photographing the undersides of mushrooms is to bring a compact mirror with you on your walks. By placing it beneath the cap, you are able to see underneath without uprooting the mushroom. Another interesting fact about the Turkey-Tail fungus is that you won’t find any other fungi on the tree upon which it grows. This is because the fungus releases chemicals that deter other species. 

My personal favorite fungi find of the walk was a honey mushroom. Honey mushrooms are a type of parasitic fungi that kills trees using their rhizomorphs or congregate bunches of fungi hyphae. They achieve this by interfering with the tree roots that would normally send nutrients to the rest of the tree. The honey mushrooms that we spotted took the form of rhizomorphs embedded in a fallen (and largely decomposing) log. Honey mushroom rhizomorphs can grow up to 1 meter a year, making them a formidable parasite. 


A Gem in the Making

A Forest Exploration find that garnered significant enthusiasm was a Polyphemus moth caterpillar (Antheraea polyphemus), a member of the family Saturniidae or giant silk moths. This caterpillar was spotted on a small oak tree off to one side of the path. The adult moths boast an average wingspan of six inches. 

During this time of year, you might find still-green leaves on the ground alongside colored leaves that have already fallen. If you inspect one of these green leaves, you will notice that the petiole, or stem, has been neatly chewed through. This incision is made by a caterpillar and is speculated to be an adaptation to avoid drawing the attention of predators such as birds. A significant patch of chewed upon leaves might alert birds to the existence of a caterpillar. If instead that caterpillar removes the leaves after feeding, the likelihood of attracting predators might be diminished. This practice of removing still living leaves is referred to as “greenfall.”


An Abrupt Ending

A couple of hours into our walk and we began to hear rumbling overhead. What started as a distant noise soon drew closer and we readied ourselves to return in order to avoid getting caught in the rain.

As we were leaving, several people in our group caught sight of a Garter snake (Thamnophis sirtalis). Garter snakes are fairly common in the Fells but I, for one, am always enchanted by their sleek beauty and seemingly confident, deliberate movements. 


This was my second Forest Exploration and I was amazed to see how quickly nature can shift and develop over the course of a single month. I look forward to continuing to familiarize myself with the Fells throughout the fall and winter. Thanks to all who joined us for this walk! You can check out our findings from the day here.

Enjoy your visit. 📅 Join our Plants and Wildlife Documentation Walks to explore the natural joys to be found in September. We will be on the lookout for signs of fall and for bird and mammal winter preparation activity.

Forest Explorations


August, 28th 2020 | by Mina Burton 

Banner photo: iNaturalist record © Joe MacIndewar. Most photos in this article are visual observations that the EwA team recorded during the August’s Forest Explorations event. Photos are licensed under Attribution-NonCommercial (CC BY-NC).

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