ST. JOHN, U.S.V.I.
Virgin Islands Environmental Resource Station
The facility is free to those who volunteer to spruce up the buildings (including the 11 wooden guest cabins) and to help scientists catalog the island's native plant species along with fish and other marine life. Day trips include mountain hikes and tours of nearby petroglyphs and former rum distilleries. islands.org/virgin/viers, open year-round, book six months in advance.
VANCOUVER ISLAND, B.C.
Clayoquot Field Station
There's plenty to study at this station in the Tofino Botanical Gardens, which has a collection of plants from southern Chile, as well as a bird sanctuary that attracts western sandpipers and great blue herons. The red-cedar station has eight rooms with bunk beds and beamed ceilings, a lounge with leather club chairs and a fireplace, and a yoga program. Guests cook their own meals in the communal kitchen. 250/725-1220, tbgf.org, from $32, open year-round.
Southwestern Research Station of the American Museum of Natural History
Scientists at this field station in eastern Arizona study native Mexican birds and hummingbirds. The three cabins sleep up to 15 people each, and meals are served in the dining hall. "Everyone sits family-style, so guests can get to know the staff," says director Dawn Wilson. 520/558-2396, research.amnh.org, $75 with meals, open spring and fall.
Churchill Northern Studies Centre
Up to six people can stay for free at the remote station if they volunteer for kitchen duty, with opportunities to plant trees and collect data [text amended, 10/13/08]. Staff researchers give lectures on the region's subarctic climate and lead regular hikes to the habitats of arctic foxes, snowy owls, and polar bears. The facility also has a 300-species herbarium and an observation dome for viewing the aurora borealis in the winter. 204/675-2307, churchillscience.ca, open year-round.
HEREDIA, COSTA RICA
Tirimbina Rainforest Center
"We pride ourselves on the center's one-of-a-kind activities, such as a tour of a cacao plantation, a twilight frog walk, and a moonlight hike to a bat habitat," says Carlos Roberto Chavarria, director of the nonprofit center in the Sarapiquí River basin. The solar-powered station accommodates 45 guests, with meals served in an open-air dining room. 011-506/2761-0333, tirimbina.org, from $64, meals from $6, open year-round.