Nashua River Watershed Association naturalist Diane Lauber will lead an expedition into forest, wetlands, and vernal pools looking for signs of life from 1 to 2:30 p.m. April 27 on the Williams Barn property at 160 Chicopee Row. The town-owned site has diverse ecosystems, and participants in the all-ages “Spring Safari’’ will be able to see what plants are budding and blooming, listen for birds, and observe signs that animals are nesting and raising their young. The cost is $8, or $24 for a family, discounted to $6 or $18 for members of the association. Preregistration is required. Contact Stacey Chilcoat, the association’s river classroom director, at 978-448-0299, or e-mail her at email@example.com.