On a fall afternoon in Inwood Hill Park, a persimmon tree sheds its golden leaves while children play baseball on a field nearby. A strong gust of wind sends dozens of leaves flying; one appears to flutter in place for a moment, then swoop up into the sky. It’s no leaf: it’s a butterfly.
Monarch butterflies, one of the best-known species with their distinctive golden-orange and black patterning, are passing through New York on their annual trip south to spend a warm winter on the volcanic mountaintops of central Mexico.
Monarch expert Dr. Karen Operhauser of the University of Minnesota’s Monarch Lab says that somewhere between 20 million and one billion monarchs will reach Mexico before the weather changes.
“It’s hard to count something when there are millions of them,” she says. “But it’s huge numbers.”
The journey, up to 3,000 miles for the northernmost butterflies, begins in mid-August and lasts through the first weeks of November. Most butterflies reach certain latitudes at about the same weeks each year, and their visit to uptown Manhattan is taking place right now.
Over the past two weeks, monarchs have been spotted in many city parks and gardens, looking for nectar before continuing south. Rangers at the Inwood Hill Park Nature Center built a small butterfly garden filled with sweet-smelling butterfly bushes, Russian sage, asters and other colorful, nectar-filled flowers to attract and feed the famished fliers. Operhauser says that preserving and creating areas that feature native flowering plants is key to the monarch’s survival.
“Just like any other species, habitat loss is a huge issue, and for something that’s a migratory animal like monarchs, habitat loss… includes wildflowers that they can get nectar from,” she says. “Monarchs can’t make that flight without eating.”
Chrissy Word coordinates programs for the Butterfly Project, a New York group that focuses on protecting pollinators in the city. The project distributes native plants each spring to gardeners, holds workshops on how to care for the plants, and even publishes a Pollinator Curriculum Guide for middle-school science classes. Word and several other nature lovers, scientists and educators launched the Butterfly Project in 2003 when they discovered a shared love of butterflies and concern about resources, which Word says is especially important in a big city.
“The landscape of New York City is an extremely urban center with lots of hard ground, concrete and buildings and very intermittent green spaces,” she says. “So butterflies, just like all wild animals, have to hazard a lot of human-made obstacles to get to where and what they need.”
The monarchs also face a challenge trying to find the specific plants they need for laying eggs. While monarchs are generalists when it comes to food, meaning they feed on any flowering plant available, they will only lay their eggs on milkweed in the spring.
Unlike the fall migration south, the spring migration back north takes place over four generations. The wintering monarchs in Mexico fly north for about a quarter of the way, then stop and lay eggs. The next generation travels the next quarter of the way, stops and lays its eggs, and so on. The fourth generation will finish the migration north and then also complete the fall migration back south starting in August.
This means that milkweed is key in all North American latitudes, but it’s getting more difficult to find, especially in the city. Milkweed grows along roadsides in New York, Word says, but gets mowed down too regularly to allow for egg laying.
“So these butterflies are really having to find locations and communities with gardens and parks where these plants are,” Word says. “Or they risk having to pass through the city and not find any food or egg-laying resources at all, and that’s a real risk.” She added, “That’s a long trip without fuel.”
Inwood Hill Park Nature Center hosts several pots of milkweed plants, which park ranger Sunny Corrao says monarchs use for egg laying because the “milk” inside the long stems is poisonous to birds and other predators, ensuring the safety of caterpillars.
Word and The Butterfly Project are looking forward to the spring when they will hold the ninth annual Native Plant Share with community, school and park gardeners in the hopes of preserving native pollinators in the concrete jungle.
Although monarchs confront increasing problems during their migration, they are still visible in uptown parks and gardens. Corrao hasn’t seen a deluge of the orange butterflies in Inwood Hill Park, she says, but she’s spotted two or three a day for the past couple of weeks, a huge increase compared to any other season.
Despite studying monarchs for more than 25 years, Operhauser still marvels at butterflies that navigate through big cities.
“It always amazes me when I see monarchs in urban areas,” she says. “It’s really something that they can find these small patches of habitat.”