What pollinators live in the city?

Have you ever wondered what kinds of pollinators like to visit urban gardens? My work this summer can help answer that question! My name is Maria Ostapovich, and I am currently a first year Master’s student at Tufts and a new member of TPI. Since the beginning of July, I have been surveying pollinators in gardens around Somerville, MA to understand 1) which pollinators occur in urban gardens and 2) which flowering plants those pollinators depend on. I surveyed pollinator-friendly gardens and ornamental gardens to see how they compared to one another.

Me surveying the ornamental garden in Powderhouse Square rotary. PC: Nick Dorian

Surprisingly, it was difficult to find public gardens (within walking distance) to survey during this project. The eight suitable gardens I found seemed like unlikely homes for pollinators: a busy bike path, a yard next to a construction site, and the middle of a rotary. But after my first survey, the opposite proved true. In the middle of the city, flowers everywhere were brimming with pollinating bees, wasps, hover flies, and butterflies.

Twice per week, I surveyed all eight gardens on foot. I made sure to pack plenty of water and wear comfortable shoes for my trek through Somerville and, by the end of each six-hour survey, I had invariably logged 10,000 steps. At each garden, I identified each flowering species of plant and counted the number of blooms. Then, I identified and counted the number of pollinator species that visited flowers, noting which species of plant they visited over 10 minutes.

First, I found that not all plants are equally attractive to pollinators. Commonly planted ornamental plants like day lilies and hostas did receive some insect visits, but native plants consistently outshone them. The white candelabras of culver’s root were particularly attractive to pollinators in June and July; cutleaf coneflower was a favorite of sweat bees and long-horned bees; and goldenrod stole the show in the fall. Native plants, clearly, were a favorite of pollinators in Somerville.

Bees love asters! Metallic green sweat bee (Agapostemon sp.), sweat bee (Halictus sp.), and the common eastern bumblebee (Bombus impatiens) on New England aster in a pollinator-friendly garden. PC: Maria Ostapovich

Overall, the insect diversity that I observed was incredible. I found insects ranging from fuzzy, clumsy bumblebees to indecisive, metallic green sweat bees. I observed cute little leaf-cutter bees holding their abdomens aloft and I saw formidable (yet harmless!) great black digger wasps. Among many other pollinators, I saw long-horned bees quickly zipping between flowers and several convincing bee-mimics including a hover fly (Spilomyia longicornis) that looks nearly identical to a European paper wasp. Surprisingly, I observed few butterflies during my surveys, perhaps a result of unfavorable conditions earlier in the year.

Male long-horned bee (Melissodes sp.) taking a break on a sunflower before zipping off. PC: Nick Dorian

I learned so much this summer, most notably how to identify urban plants and pollinators! For any tips for identifying pollinators on your own, check out TPI’s identification guides. While it was fun to learn how to identify so many species, it was even more exciting to see what kinds of plant-pollinator interactions took place across these gardens. Although the data analysis is still ongoing, I will be able to generate lists of plants that pollinators like and dislike as well as document the weeks of the year during which plants are flowering and pollinator species are most active. These findings will be coming soon after I complete my surveys (which are continuing until frost reaches Somerville) and after I learn the best way to analyze my data. Make sure to keep an eye out for additional blog posts sharing more of my findings!

To learn more about our ongoing efforts to document urban pollinator biodiversity, get in touch with us through social media or tuftspollinators@gmail.com!

On feeding hungry monarchs

A migrating monarch feeding on seaside goldenrod in Gloucester, MA. PC: Rachael Bonoan.

Fall is a time for migration in the North, as animals flee the bitter cold of winter in favor of warmer regions. If you’ve been outside in New England in the past few weeks, you’ve probably been in the presence of these migrants. Birds are some of the best known long-distance migrants, but plenty of insect pollinators embark on similarly stunning journeys each fall, in spite of their diminutive size. Some are inconspicuous and elusive, like the various species of hover fly whose migration through our region has only been recorded a few times in the past hundred years; others, like the monarch butterfly, are beloved signs of the closing of summer.

Each fall, millions of these large orange and black butterflies form a remarkable caravan, as monarchs from breeding grounds across a range that stretches as far north as Nova Scotia embark on the long flight to the overwintering grounds in central Mexico. These migratory monarchs need to reach dwindling undisturbed patches of oyamel fir forest, where they spend much of the cool winter perched in massive clumps on the trees, largely quiescent. There they wait for warmer temperatures that signal the arrival of Spring, when they can depart and gradually begin their multi-generational recolonization of the breeding range.

Surviving the 3000+ miles of flight and the subsequent months of cool winter in Mexico requires energy, and lots of it. The butterflies – weighing about a fifth of a penny – bulk up on nectar by gorging for hours on fall-blooming flowers. So efficient are their digestive systems that it’s thought that the sugars in the nectar can be converted into energy-rich fat stored in a special organ in a matter of minutes. Monarchs most likely need to more than double their regular fat stores during migration in order to survive the winter, meaning that stunningly, these butterflies actually gain weight during their multi-thousand-mile-journey. 

Two migrating monarchs on an aster species (Symphyotrichum sp.). In the fall, males and females are non-reproductive; they happily feed on the same plants and often roost together during migration. PC: Rachael Bonoan

You may have heard that monarch butterfly populations have suffered steep declines in recent years, with most estimates putting the losses in the Eastern population over 80%. A broad set of human actions have conspired against the monarchs, including deforestation in Mexico and agricultural herbicide use in the Midwest. Recently, ecologists have raised the specter of a third challenge: increased mortality during migration.

Migration is a dangerous undertaking, and biologists speculate that perhaps as many as 95% of monarchs attempting to migrate perish each year. As meadows and prairies have been converted to asphalt and crops, native grassland habitats that support large numbers of fall-blooming flowers are a dwindling commodity. Some ecologists posit that a lack of nectar along the migration route could be leading to starvation during the flight or in the quiescent overwintering period.

This is where we come in. Through planting gardens that can continue producing flowers all the way through October, we can provide valuable resources not just for monarchs but for all the other pollinators that are still flying. Surviving and thriving at this time of year in New England can be a tenuous proposition for animals that eat nectar and pollen: nighttime temperatures flirt with freezing and many of the flowering plants in our region have already gone to seed or begun senescing by September. In a summer with a drought like the one we’ve had in Massachusetts this year, wildflower outlooks can be even grimmer by the time October swings around. 

But where there is a tenuous situation, there is also an opportunity for our interventions to make a bigger difference. Much of the land in New England would, given the chance, burst into late-fall bloom every year in a riot of goldenrods and asters, pumping out nectar and pollen through until frost.  These native, pollinator-friendly species are conveniently often exceedingly drought-tolerant and some grow aggressively when given the chance, like the goldenrod species in the picture below:

A vacant lot in Rhode Island, September 2020, brimming with goldenrod. PC: Atticus Murphy.

Crucially, these patches can arise in the middle of neighborhoods on vacant lots or road verges, providing unexpected oases for fall-flying insects. Likewise, by carefully planning gardens that bloom continuously until the end of September, gardeners can provide nectar not only for migrating monarchs, but the hundreds of other pollinator species that require pollen during the fall. 

Adding autumn-blooming flowers amounts to starting a food bank for pollinators like monarchs, and by planting easy-to-grow native perennials like goldenrods and asters, the food bank will return every year, essentially for free! Migration is hard enough without pesky human interference; let’s try and help these iconic butterflies along their way, if we can.

Urban Boston Fall Pollinator BioBlitz!

This weekend, September 26-27, 2020, join TPI for a fall pollinator bioblitz! If you live in the city around Boston (east of I-95) get out during the weekend to observe pollinators—bees, butterflies, hover flies, wasps, and beetles—and post your sightings to iNaturalist. There will be so many insects to see, including monarch butterflies, bumble bees, paper wasps, goldenrod beetles, and more! If you’re not familiar with iNaturalist, see this guide for getting started.

During the bioblitz, TPI biologists will be scouring the flowers in our gardens on the Tufts University Medford-Somerville campus. We hope you’ll get out in your yard or neighborhood to look for pollinating insects, too. Your participation in this bioblitz will help TPI biologist better understand how gardens support pollinators in the city.

Never participated in a bioblitz before? Here are some tips to get you started: