Pizzeria Rustica Cycling Club — 2 p.m. second Sundays, Pizzeria Rustica, 2527 W. Colorado Ave.; pizzeriarustica.com.
Monarch Crest Crank — 8 a.m.-4 p.m., Monarch Crest Trail and Riverfront Park, Salida, $85. Registration: monarchcrestcrank.com/registration.
Fall Colors Multi-Day Cycling and Photography Tour — Begins 2 p.m., Snowmass Village. Cost and registration: tinyurl.com/yyovx7tl.
Nature and Wildlife Discover Center — 9112 Mountain Park, Beulah. Register: hikeandlearn.org.
• Autumn Equinox Hike, 9 a.m.-noon Sunday, $5-$10.
Mueller State Park — 21045 Colorado 67, Divide. Day pass $8 per vehicle; 687-2366.
• Aspen and School Pond, 8 a.m. Tuesday, School Pond Trailhead.
• School Pond and Stoner Mill, 9 a.m. Tuesday, School Pond Trailhead.
• Elk Meadow an Peak View Pond, 8 a.m. Thursday, Elk Meadow Trailhead.
• Cahill and Buffalo Rock, 8 a.m. Saturday, Grouse Mountain Trailhead.
• Turkey Cabin Overlook, 9 a.m.Saturday, Camper Services.
• Elk Bugling, 6:15 p.m. Saturday, 5:30 p.m. Sept. 26, Grouse Mountain Trailhead.
• Homestead, 2 p.m. Sunday, Homestead Trailhead.
Rocky Mountain Conservancy Field Institute — 1895 Fall River Road, Estes Park. Register: rmconservancy.org.
• Photographing the Wildlife of Kawuneeche, Thursday-Saturday.
Nature and Raptor Center of Pueblo — 5200 Nature Center Road, Pueblo. Register: hikeandlearn.org.
• Weekend Raptor Talks, 11:30 a.m.-noon Saturdays-Sundays, free.
Mueller State Park — 21045 Colorado 67, Divide. Day pass $8/vehicle; 687-2366.
• Touch Table: Aspen, 3 p.m. Saturday, Visitor Center.
• Touch Table: Horns and Antlers, 10 a.m. Sunday, Visitor Center.
Bear Creek Nature Center — 245 Bear Creek Road. Register: 520-6387; tinyurl.com/yarxcazm.
• Same Tree Different Day, 6:30-8 p.m. Tuesday, $5.
• Aiken Audubon Monthly Program, 6:30-8:30 p.m. Wednesday, free.
Florissant Fossil Beds National Monument — Florissant, entrance fee, $10 for 16 or older; 748-3253.
• Night Sky Program, 7:30-9:30 p.m. Friday, Visitor Center.
Achilles International Pikes Peak Running Club — Nonprofit that uses the power of running to bring hope, inspiration and joy of achievement to people with disabilities, 6:15 p.m. meet and sign in; 6:30-7:30 p.m. run, walk or wheel, Mondays, Colorado Running Co., University Village Center, 5262 N. Nevada Ave., Suite 140; Laura, 331-1011.
Pikes Peak Road Runners — Cost and registration: pprrun.org.
• HEARS 5K Experience, 8:30 a.m. Saturday, Bear Creek Park East.
• Be Ovary Aware 5K Run and 3K Walk, 8:30 a.m. Sunday, America The Beautiful Park.
North Cheyenne Cañon Park — Help with outdoor education at Starsmore Visitor and Nature Center; Aaron Rogers, 385-6089, email@example.com.
Bear Creek and Fountain Creek nature centers — Help with environmental education and visitor information; Paula Megorden, 520-6387, firstname.lastname@example.org.
Eleven Mile — Volunteer to help facilitate children’s craft and educational programs on Saturday mornings; Kristen, 748-3401, email email@example.com.
Colorado Wolf and Wildlife Center — Volunteers needed to work in the visitor center, grounds- keeping, leading tours and more, 4729 Twin Rocks Road, Divide; 687-9742.
Listings are published on a space-available basis. Email information at least two weeks in advance: firstname.lastname@example.org.