By May, summer is just around the corner at Fresh Pond, and the month sees a boom of insect life at Lusitania Meadow. Along with this late-spring boom comes all kinds of activity, from the nesting of mining bees to the arrival of insect-eating warblers. By late May, the air here and in the many wild areas of Massachusetts will be buzzing with insects. It’s an incredibly exciting time of year to be a naturalist around here, with a full transition from the introspective focus of winter and early spring to the almost overwhelming multitude of organisms that can be found at Fresh Pond throughout the summer.
“Observing the changes in nature and the rest of our environment throughout the seasons is one of the most joyful things about living in New England. Whether I’m taking in a buzzing bee metropolis on a patch of goldenrod, breathing steam on a walk around an iced-over pond, or feeling the air come alive on our first warm spring day, I’m always happy when I’m observing nature’s changes like this. These natural rhythms give us a place to find solid ground, whatever we might be going through.”
EwA citizen scientists and interns survey the Lusitania meadow 📍 for arthropods every single week during the warm seasons. During the colder months, we explore the general biodiversity of the reservation in more detail. This gives us the opportunity to get to know the meadow and its surroundings intimately. Each week highlights different relationships between the plants and their visitors—fascinating stories unfold. This almanac is a wonderful means to share with our communities what we observe and record at Lusitania over the course of the year.
📅 Once a month, we open EwA documentation sessions to the public. Check us out on Eventbrite and come experience with us the magic of this wonderful meadow—an oasis in the middle of a very busy city.
May marks the first month of the year in Boston that sees virtually no chance of an overnight freeze, and these consistently warmer temperatures bring with them an explosion of plant growth. The average monthly low temperature for May in Boston is 5.1ºC (41.2ºF), up a crucial six degrees from April’s -0.6ºC (31.0ºF). Boston’s average daily high in May is 19.2ºC (66.5ºF), with an average daily low of 10.2ºC (50.3ºF). The area sees over 15 hours of daylight by the end of May, before day lengths peak around the solstice in June. May is the first month in the Boston area that sees an average ultraviolet index in the hazardous range, meaning that you should take precautions to protect against skin and eye damage if you’re out in the field during the middle of the day.
One flower that can be found at Lusitania Meadow in May is wild geranium (Geranium maculatum). Wild geranium can be recognized by its palmate leaves with 5 very pronounced lobes, and by its small purple flowers with five rounded petals. Wild geranium leaves are basal, growing from the root of the plant. The stem that eventually bears a wild geranium’s flowers grows separately from the leaves, showing up a couple weeks later. Wild geranium is a woodland plant, and on a visit to Fresh Pond you can find it both at the edges of Lusitania Meadow and on the forest floor further into Lusitania Woods. By mid-May, you should be able to find wild geranium flowers on your visit to the Reservation.
Like many other wildflowers, wild geraniums spread their seeds by ballistic dispersal. At the base of each of the plant’s flowers is an elongated pistil which is sometimes referred to as a “crane’s bill” (although this nickname is also used to refer to the entire plant). Wild geranium flowers are bisexual but go through separate male and female phases to avoid self-fertilization. When the plant has a recognizable flower with its five petals, it is usually in the male phase, with pollen present on the mature stamens. After sufficient insect pollination, the flower drops its pollen and transitions to the female stage quite rapidly, sometimes in just a few hours. The plant loses its petals shortly after fertilization. As the remaining seedpod matures, the tissues on the outside of the pod contract at a faster rate than those on the inside. This results in a building tension in the outside of the pod, which is connected to the stem only at its very top and bottom. Eventually, this tension is enough that the five “arms” of the pod pull away with enough force to send the mature seeds flying.
You might observe a variety of insect visitors and residents on wild geranium. Some caterpillars are known to feed on wild geranium leaves, including those of the winter moth Erannis tiliaria (not to be confused with the related, but invasive winter moth Operophtera brumata). Winter moth females, which mature later in the year, are wingless and rely on pheromones to attract male mates. Wild geranium flowers have many beetle visitors as well, with weevils (family Curculionidae) being the predominant ones. The invasive Japanese beetle (Popillia japonica) is also attracted to wild geranium, and the flower’s fragrance is sometimes used in trapping them. The wild geranium’s most frequent pollinators are honey bees and mining bees (family Adrenidae).
🔎 Nature Quest » Looking for Mining Bees
Mining bees are an incredibly diverse family of bees, with thousands of species worldwide, and our native New England mining bees play an important role in the pollination of our local native plants. Often, a species of mining bee will have a close relationship with a specific type of plant which it has evolved alongside for millennia. Western honey bees (Apis mellifera), which are in fact not native to New England and originated in Europe, are generalists and don’t have such close and specialized relationships with the plants of the area.
Mining bees are solitary bees named for their underground burrows. In these burrows, female mining bees excavate a series of cells, which they fill with pollen and nectar before laying an egg inside and sealing. Mining bees can be recognized by the patch of hair between their eyes, which does not occur in other bee species of their size. See if you can spot mining bees or their burrows around Lusitania Meadow as the flowers begin to bloom in June!
Migrating May Warblers
The approach of summer brings the last, and in some ways most spectacular, stages of annual bird migrations to and through New England. Larger migratory birds, such as herons and waterfowl, have already arrived or passed through Massachusetts by the time May rolls around. But for the wood-warblers (family Parulidae), May marks the height of migration season in Massachusetts. These often brilliantly colored birds have a wide variety of behaviors and lifestyles, and May presents a great opportunity to observe them around Fresh Pond.
Wood warblers are a complex family of birds, containing 119 currently-described species. Warblers tend to be narrowly specialized in terms of their diet and occupy narrow ecological niches. The different ecological niches of warblers can often be inferred from the subtle differences in beak shape, much like the Galapagos finches that were a significant influence on Charles Darwin’s theory of evolution. Galapagos finches have much more dramatic beak differences than our warblers, which caused Darwin to infer that their beaks had adapted over time to suit the diverging diets of finch populations as they differentiated into new species.
While the majority of the warblers you can observe at Fresh Pond in May are just passers-through, some of them might be settling down for the nesting season as well. Often, warblers require one type of habitat for nesting and another for feeding, which makes this group of birds especially vulnerable to habitat fragmentation. Some of the mixed habitats around Fresh Pond do suit certain warblers, though, and these are more often found on the Reservation than other warblers. Some of the warblers you’re most likely to see around Fresh Pond are ovenbirds (Seiurus aurocapilla), American redstarts (Setophaga ruticilla), and the friendly yellow warbler (Setophaga petechia). Yellow warblers tend to be less wary of humans than other warblers, and their arrival at Fresh Pond presents an excellent opportunity to observe the behavior of these birds.
The Yellow Warblers arriving at Fresh Pond in May have arrived from wintering grounds that range as far south as Venezuela, Colombia and Ecuador. Yellow warblers are easily recognized, as they are the only warblers who appear entirely yellow from a distance that breed in New England. On closer inspection, though, male yellow warblers can be distinguished by the rusty streaks on their breast. As males arrive, a week or two before females, they immediately start establishing breeding territory. Females, once they have selected their breeding territory, often must withstand some harassment from the territorial males before they are accepted as a mate and the territorial behavior is focused elsewhere.
Caterpillars are a favorite food of yellow warblers, and form a large part of their diet. In fact, these birds often feed heavily on pests like gypsy moth caterpillars (left 📸 ), so make sure to thank a yellow warbler the next time you see one. Other prey of the yellow warbler include midges, spiders, and beetles. The birds hunt bugs in two manners, both gleaning prey off of plants and catching them on the wing.
Yellow warblers are frequent victims of brood parasitism by the brown-headed cowbird (Molothus ater), which lays eggs in other birds’ nests. Nest parasitism occurs at an alarming rate: studies put the figure at 40% of all yellow warbler nests. These warblers have a clever, brute-force response to this issue. If their nest has been parasitized by a cowbird before too many eggs have been laid, a yellow warbler will often simply build another nest on top of the old nest, sealing it and the cowbird’s eggs away, and lay a new brood. This cowbird-yellow warbler conflict can escalate to humorous effect, with this process once being observed nine times in a single nest, resulting in a huge, ten-level structure. Of course, a cowbird’s persistence often pays off, though, and if the warbler has laid more than three eggs before the cowbird visits, the warbler will usually raise the cowbird chick as one of its own.
Yellow warblers don’t stay on their breeding ground in Massachusetts for very long. By the time the chicks have fledged in summer, the parents are ready to vacate their summer home and begin preparing for the journey southward. By July, migratory movements will begin, and Fresh Pond will lose its brilliantly-colored and friendly summer residents. By the end of May, summer is approaching fast, but it won’t last forever. A visit to Fresh Pond is a great way to attune yourself to the bustle of these months, and to take them in before they’re gone.
Of course, there is so much more to enjoy in May at Lusitania! Go check for yourself and enjoy your visit. 📅 Join any of EwA’s biodiversity walks in the area. Share your findings with us (you can comment below)! We will be back next month with a new slice of life in the meadow.
EwA Useful Links
🦆 Birds of Lake, P, and Marsh: Water and Wetland Birds of Eastern North America (1999) by John Andrew Eastman.
🌿 The Book of Field and Roadside: Open-country Weeds, Trees, and Wildflowers of Eastern North America (2003) by John Andrew Eastman.
May, 11th 2020 | by Mike McGlathery
Banner photo, editing & layout by Claire O’Neill. All the in-text species photos in this article are visual records that the EwA team collects at our various study sites, including at Fresh Pond. Click on any picture and you will land on the record and its owner. Photos are licensed under Attribution-NonCommercial (CC BY-NC). See EwA’s biodiversity occurrence records specific to this place in the EwA at Fresh Pond iNaturalist project.
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