Early fall at the Fells bears signs of the changes to come. Leaves are beginning to take on warmer hues and the summer’s fruits are largely finished. While some of nature’s activities are winding down, others, such as bird migration, pick up during this time of year. During our walk, we enjoy heightened bird activity from year-round Wood pewees (Contopus virens) and White-breasted nuthatches (Sitta carolinensis) to Black-throated blue warblers (Setophaga caerulescens) passing through on their migratory path. Much of the Fell’s flora has passed its summer prime but evergreen wintergreens still adorn the forest floor.
“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 month, we began our Forest Exploration with a brief discussion of the various habitats of the Fells. The Fells supports at least 33 habitats spanning from oak-hickory and aspen-birch forests to emergent freshwater marshes and vernal pools. Much of the Fells was once divided up into pastures, farms, and forests used for timber. You can still see remnants of past pastures indicated by the occasional stone wall scattered throughout the reservation.
The Challenge of Identifying Oaks
Much of the forest canopy at the Fells is composed of oak trees. These ecologically significant trees support more than 500 species of moths and butterflies, provide shelter and food for squirrels and birds, and host a wide variety of galls.
Even as I become more familiar with the Fells and its flora, I still struggle to differentiate between oak species. During our Forest Exploration, I learned that this is in part because oaks often hybridize, making it hard to pin them down to the species level. Furthermore, the bark of trees evolves over their lifespans; what may begin as a relatively smooth bark may grow increasingly furrowed over time. Despite these complicating factors, Claire and several of our attendees offered some practical tips for identifying oaks.
↑ White oak (Quercus alba) leaves are round-lobed, compared to the more jagged margins of red and black oak trees. Their bark appears as long ridges with intersections, which one attendee, Tinie, helpfully described as “longitudinal islands.”
↑ Red oaks sport leaves with sharper margins than those on white oaks. The bark of red oaks displays long vertical lines, similar in appearance to ski slopes.
↑ We observed the bark of this black oak as having smaller “islands” than that of the white oak. However, as stated earlier, there exists variation and hybridization even between oaks in the same family.
The Three Wintergreens
↑ Spotted wintergreen (Chimaphila maculata) (left) is a common resident at high elevations in the Fells and is an indicator of a healthy ecosystem. During our July Forest Exploration, this evergreen plant bore beautiful flowers featuring five white petals clustered around a jewel-like green pistil. Now only the dark, waxy leaves remain.
During our walk, we were fortunate to spot two other species of wintergreens that are less common at the Fells; Pipsissewa (Chimaphila umbellata) (center) and American wintergreen–also known as–Round-leaved Pyrola (Pyrola rotundifolia) (right). Unlike Spotted wintergreen and Pipsissewa, the American wintergreen is not an evergreen.
An Accidental Detour
Rogue trails, or non-official trails created by foot or bike traffic, pose a huge problem at the Fells. These compacted trails are obstacles to the movement of certain species, such as salamanders, and offer new corridors for predation and invasives. The tricky thing about rogue trails is that they aren’t always easy to distinguish from official trails, even for those familiar with them. At one point, our group turned off onto a path that devolved into a narrow, uneven descent. Though we soon realized we had mistakenly taken a rogue trail and backtracked, our misstep goes to show just how difficult it can be to avoid rogue trails. EwA has upcoming plans to partake in a mapping project intended to distinguish between official and non-official trails.
A Closer Look at Pines
In addition to oaks, white pines are another fairly common tree species at the Fells. Baby pine tree branches offer a surprising amount of information about trees and the conditions they grow in. The trunk space between every branch indicates one year – shorter gaps between branches likely indicate that the growing conditions that year were unfavorable.
While insect activity on pines can prove more elusive to the human eye than on oaks, for instance, Kathy pointed out an indicator of moth activity on several of the pines we passed. The photo on the right shows a clump of pine needles created by a Pine tube moth (Argyrotaenia pinatubana). These species of moths spin silk to tie together between five and twenty pine needles, creating a tube in which larvae can live and feed. In their pupal stage, the moths can also overwinter in these tubes.
In addition to providing shelter while attached to trees, pine needles also offer refuge once they fall to the forest floor by providing a soft carpet. This layer is especially useful in the winter, as it provides an additional layer of insulation alongside accumulated snow. Pine needles are tannic and therefore create an acidic soil environment once they fall. While acidic soil isn’t opportune for many species, it does create a unique habitat that is especially conducive to the growth of plants in the heath family such as blueberries, huckleberries, wintergreens, mountain laurels, and ghost pipes.
An Upside-Down Approach
One of my personal favorite birds at the Fells are White-breasted nuthatches, in part because they are one of the few birds I can regularly identify. I spent a portion of my internship fieldwork this past summer learning to recognize birds by their calls. This task was challenging and I am still far from mastering it. I appreciate that I can recognize White-breasted nuthatches not by their calls or even appearance, but by their distinctive movements.
White-breasted nuthatches feed head down, making them quite fun to watch. Like woodpeckers, they feed by maneuvering along the trunks and branches of trees. Woodpeckers, however, have a different claw structure with two front and two back claws. White-breasted nuthatches instead have three front and one back claw similar to those of a regular perching bird. The ability to move upside down is also unique to the White-breasted nuthatch. It is speculated that this different vantage point may give the nuthatch an advantage over the woodpecker in that it is able to clearly examine a tree’s trunk from above and below, perhaps allowing it to spot insects a woodpecker might miss.
Galls: Full Room and Board
Galls often garner significant attention during our walks. These growths are common throughout the Fells and come in a surprisingly broad array of shapes, colors, and textures.
Wool Sower Gall Wasp (Callirhytis seminator)
Galls are growths of plant matter that result from a chemical interaction between a tree and a fungus, insect, or bacterium. In the case of insects, the gall serves as both a home and food source for the larvae until the insect is developed enough to exit the gall. All three of the following galls are created by wasps, yet are radically different in their morphologies.
I greatly look forward to continuing to attend and write about EwA’s Forest Explorations throughout the year. While spring and summer may appear to be more lively in terms of natural phenomena, the Fells offers exciting activity throughout the cooler months as well. As always, thank you to everyone who attended this month’s walk! You can explore other findings from September’s Forest Exploration here.
📅 Join us next month to explore the natural joys to be found in October. We will be on the lookout for the activity of insects taking advantage of the last warm days of the year and signs of winter preparation.
September, 18th 2020 | by Mina Burton
The photos of species in this article are the visual observations that the EwA team recorded during the September Forest Explorations event (@ Mina Burton, © Bill MacIndewar, @ Joe MacInderwar, @ Claire O’Neill). Click any photo and see the corresponding record in EwA’s iNaturalist Fells project (and its author). Photos are licensed under Attribution-NonCommercial (CC BY-NC).
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