Join the Friends of Princeton Open Space (FOPOS) and expert birder Winnie Hughes Spar for a guided bird walk through the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ. Together, we will observe Princeton's birds and learn about their fascinating habits!

BYO: Bring binoculars and water. Wear comfortable hiking shoes or sneakers; the trails can get muddy, especially around the lake.

Register for the Fall Bird Walk

Join us for our August Nature Walk through the trails of the Billy Johnson Mountain Lakes Nature Preserve.

Led by the Friends of Princeton Open Space summer interns, we'll observe the great diversity of life at the Preserve with possible sightings of eastern painted turtles, great blue herons, beavers, salamanders, crayfish, and macroinvertebrates. Learn about various plant species and habitat restoration projects aimed at preserving native organisms. After our walk, we’ll head back to the Mountain Lakes House to delve into the world of macroinvertebrates collected during our walk. Using field microscopes, we'll explore the diversity of plants & waterbugs and discover their role as indicators of ecosystem health.

Sign up for our August 21 Nature Walk on Eventbrite

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Wednesday, August 19th. There will be a volunteer session from 3 pm to 5 pm. Bring a friend, and groups are welcome!

Join us for our August Nature Walk through the trails of the Billy Johnson Mountain Lakes Nature Preserve.

Led by the Friends of Princeton Open Space summer interns, we'll observe the great diversity of life at the Preserve with possible sightings of eastern painted turtles, great blue herons, beavers, salamanders, crayfish, and macroinvertebrates. Learn about various plant species and habitat restoration projects aimed at preserving native organisms. After our walk, we’ll head back to the Mountain Lakes House to delve into the world of macroinvertebrates collected during our walk. Using field microscopes, we'll explore the diversity of plants & waterbugs and discover their role as indicators of ecosystem health.

Sign up for our August Nature Walk on Eventbrite

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Saturday, August 15th. There will be a morning session from 9 am to 11 am. Bring a friend, and groups are welcome!

REGISTER FOR NATURE JOURNALING MEETUP

We'll meet at Mountain Lakes House to draw from nature in a playful and non-judgmental setting. This meetup is FREE, although registration is required. The program is designed for adults and older teens. Younger participants (under 16) are welcome to join if accompanied by an adult.

What is a meetup and how is it different from a class? While a class is a structured learning environment with a defined curriculum, schedule, projects, and goals, a meetup is a gathering of people with shared interests who get together, often with a facilitator (in this case Eleni Litt).

Meetup Location: Mountain Lakes House

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Saturday, August 8th. There will be two sessions: the morning session will be from 9 to 11 am and the afternoon session is from 12 to 2 pm. Bring a friend, and groups are welcome!

Join us at Mountain Lakes House to discuss "Wild Dark Shore" by Charlotte McConaghy. Following the discussion, we will have a demonstration on native seed collection and propagation.

This series is presented in partnership with the Princeton Public Library and the Princeton Environmental Film Festival, and is dedicated to readings about conservation, stewardship, and our relationship with nature.

Sign up for this session via Princeton Public Library. You do not need to be a library cardholder to register.

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Wednesday, August 5th. There will be a morning session from 9 am to 11 am. Bring a friend, and groups are welcome!

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Saturday, July 25th. There will be two volunteer sessions; the morning session is from 9 a.m. to 11 a.m., and the afternoon session is from 12 p.m. to 2 p.m. Come to one or both. Bring a friend and groups are welcome!

Sign up for Moth Night via Eventbrite.

Celebrate Moth Week with Friends of Princeton Open Space!

Join FOPOS's stewardship team for an evening moth survey at the Billy Johnson Mountain Lakes Nature Preserve. Moths are fascinating creatures and contribute vital ecosystem services as pollinators and as prey, especially so for baby birds, which primarily rely on caterpillars and other insects for food.

During this session, participants will observe, identify, and learn more about these mysterious night creatures. The program will begin with an educational presentation about moths, led by Patrick Natale, Assistant Professor of Biology at Mercer County Community College, followed by a hands-on activity where participants will log biodiversity data at the Preserve.

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Wednesday, July 8th. There will be an afternoon session from 3 pm to 5 pm. Bring a friend, and groups are welcome!

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Sunday, July 19th. There will be an afternoon session from 12 p.m. to 2 p.m. Bring a friend, and groups are welcome!

Sign up for this session via Eventbrite.

Wineberries are one of New Jersey's most abundant summer brambleberries, but they are also very invasive and outcompete native plants. Fortunately, they are delicious and YOU can help us curb their spread by eating them!

Join local experts Matt and Shannon for a wineberry forage walk at the Billy Johnson Mountain Lakes Nature Preserve in Princeton. During this volunteer stewardship session, participants will learn about the origins of wineberry and how to identify this invasive plant--and then we will get picking! Folks will get the chance to take their wineberry harvest home. A recipe card will be included so that you can make wineberry jam at home!

Join us for our July Nature Walk through the trails of the Billy Johnson Mountain Lakes Nature Preserve.

Led by the Friends of Princeton Open Space summer interns, this guided walk will offer a chance to explore lush trails and vibrant summer blooms. Whether you’re a seasoned hiker or a first-time visitor, it's the perfect way to enjoy the outdoors and reconnect with nature. Our stewardship team will also share insights into the history of the preserve and the ongoing land stewardship efforts that help protect this special place for future generations.

Be sure to wear sturdy, weather-appropriate footwear. Feel free to bring a camera or binoculars along to help you spot and capture the beauty of wildlife as we explore.

Sign up for our July Nature Walk on Eventbrite

REGISTER FOR NATURE JOURNALING MEETUP

We'll meet at Mountain Lakes House to draw from nature in a playful and non-judgmental setting. This meetup is FREE, although registration is required. The program is designed for adults and older teens. Younger participants (under 16) are welcome to join if accompanied by an adult.

What is a meetup and how is it different from a class? While a class is a structured learning environment with a defined curriculum, schedule, projects, and goals, a meetup is a gathering of people with shared interests who get together, often with a facilitator (in this case Eleni Litt).

Meetup Location: Mountain Lakes House

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Saturday, July 11th. There will be an afternoon session from 12 p.m. to 2 p.m. Bring a friend, and groups are welcome!

This event is postponed until Sunday, July 19th to allow more time for the berries to ripen.

Wineberries are one of New Jersey's most abundant summer brambleberries, but they are also very invasive and outcompete native plants. Fortunately, they are delicious and YOU can help us curb their spread by eating them!

Join local experts Matt and Shannon for a wineberry forage walk at the Billy Johnson Mountain Lakes Nature Preserve in Princeton. During this volunteer stewardship session, participants will learn about the origins of wineberry and how to identify this invasive plant--and then we will get picking! Folks will get the chance to take their wineberry harvest home. A recipe card will be included so that you can make wineberry jam at home!

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Wednesday, July 8th. There will be a morning session from 9 am to 11 am. Bring a friend, and groups are welcome!

RESERVE YOUR SPOT

Celebrate Juneteenth 2026 in Nature!

Join FOPOS’s Stewardship Team on June 19 for a special Juneteenth Nature Walk as we celebrate freedom, culture, community, and outdoor wellness in the Preserve. This guided walk offers an opportunity to honor the legacy of Juneteenth while connecting with the natural world and reflecting on the importance of access to green spaces, stewardship, and community.

Led by our summer stewardship interns, the walk will also recognize National Pollinator Month as we explore the fascinating role of native pollinators in sustaining healthy ecosystems. Along the trails, we’ll discover pollinator hotspots, learn about the wildflowers, shrubs, and trees that depend on them, and observe bees, butterflies, and other pollinating species in action.

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Saturday, June 13. There will be two volunteer sessions; the morning session is from 9 a.m. to 11 a.m., and the afternoon session is from 12 p.m. to 2 p.m. Come to one or both. Bring a friend and groups are welcome!

Join us at Mountain Lakes House to discuss "North Woods" by Daniel Mason.

This series is presented in partnership with the Princeton Public Library and the Princeton Environmental Film Festival, and is dedicated to readings about conservation, stewardship, and our relationship with nature.

Sign up for this session via Princeton Public Library. You do not need to be a library cardholder to register.

REGISTER FOR NATURE JOURNALING MEETUP

We'll meet at Mountain Lakes House to draw from nature in a playful and non-judgmental setting. This meetup is FREE, although registration is required. The program is designed for adults and older teens. Younger participants (under 16) are welcome to join if accompanied by an adult.

What is a meetup and how is it different from a class? While a class is a structured learning environment with a defined curriculum, schedule, projects, and goals, a meetup is a gathering of people with shared interests who get together, often with a facilitator (in this case Eleni Litt).

Meetup Location: Mountain Lakes House

Join the Friends of Princeton Open Space (FOPOS) and local foraging experts for a Mugwort Foraging Event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton.

In this hands-on event, participants will delve into the world of the invasive plant, Mugwort. Under the guidance of our stewardship team and local foraging experts Matt and Shannon, participants will learn how to properly identify mugwort, sample a recipe, and safely remove it from designated restoration areas at the preserve. From teas to donuts to savory dishes, discover how mugwort can enhance your kitchen creations.

Sign up for this session via Eventbrite.

RESERVE YOUR SPOT

Join the Friends of Princeton Open Space (FOPOS) and expert birder Winnie Hughes Spar for a guided bird walk through the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ. Together, we will observe Princeton's birds and learn about their fascinating habits!

Space is limited to 20 participants; be sure to sign up in advance. Please note that this event is geared towards adults.

Photo Credit: Xintong “Equinox” Si

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Saturday, May 30th. There will be two volunteer sessions; the morning session is from 10 a.m. to 12 p.m., and the afternoon session is from 1 p.m. to 3 p.m. Come to one or both. Bring a friend and groups are welcome!

Join us for our May Nature Walk through the trails of the Billy Johnson Mountain Lakes Nature Preserve.

Led by the Friends of Princeton Open Space stewardship team, this guided walk will offer a chance to explore lush trails, vibrant spring blooms, and the sights and sounds of nature as the season comes alive. Whether you’re a seasoned hiker or a first-time visitor, it's the perfect way to enjoy the outdoors and reconnect with nature. Our stewardship team will also share insights into the history of the preserve and the ongoing land stewardship efforts that help protect this special place for future generations.

Be sure to wear sturdy, weather-appropriate footwear. Feel free to bring a camera or binoculars along to help you spot and capture the beauty of wildlife as we explore.

Sign up for our May Nature Walk on Eventbrite

REGISTER TO VOLUNTEER

Join FOPOS for a community volunteer event at the Billy Johnson Mountain Lakes Nature Preserve in Princeton, NJ.

Volunteers will work with the stewardship team at forest or riparian restoration project sites on critical tasks such as invasive species removal, native planting, and installing cages around native plants to protect them from deer & beaver browse.

Volunteer with Friends of Princeton Open Space on Saturday, May 16th. There will be two volunteer sessions; the morning session is from 10 a.m. to 12 p.m., and the afternoon session is from 1 p.m. to 3 p.m. Come to one or both. Bring a friend and groups are welcome!

RESERVE YOUR SPOT

Join the Friends of Princeton Open Space (FOPOS) and eco-artist Susan Hoenig on Monday, May 11th at 11:00 AM for a guided nature walk and exhibition that brings together art, ecology, and conservation. Learn how we can all play a role in protecting American beech trees and the forest ecosystems that depend on them. Explore the beauty of American beech trees through a special indoor exhibition, then step outside for a guided nature walk to a beech grove in John Witherspoon Woods.

Along the way, learn how these remarkable trees support entire forest ecosystems and why they are increasingly at risk from Beech Leaf Disease (BLD), a fast-spreading threat that can weaken and kill infected trees. Hear directly from the FOPOS stewardship team about the work underway to protect these vital trees and forest ecosystem.

REGISTER FOR NATURE JOURNALING MEETUP

We'll meet at Mountain Lakes House to draw from nature in a playful and non-judgmental setting. This meetup is FREE, although registration is required. The program is designed for adults and older teens. Younger participants (under 16) are welcome to join if accompanied by an adult.

What is a meetup and how is it different from a class? While a class is a structured learning environment with a defined curriculum, schedule, projects, and goals, a meetup is a gathering of people with shared interests who get together, often with a facilitator (in this case Eleni Litt).

Meetup Location: Mountain Lakes House