Fossil Creek Reservoir is the centerpiece of 1,398-acre Fossil Creek Natural Area on the west side of Interstate 25 just south of Fort Collins. The once-private 754-acre lake, with a total storage capacity of 11,100 acre-feet, includes water from the Cache la Poudre River as well as treated wastewater. Stored water is mostly used for irrigation. The large reservoir offers few recreational opportunities with only hiking on four trails and wildlife watching to minimize human impact on wildlife. The area is managed for birds that live on both shortgrass prairie and the lake, including over 180 bird species like Canada geese, grebes, ospreys, and bald eagles.
- The natural area is a designated National Aubudon Society Important Bird Area with critical habitat for nesting and roosting migratory and resident birds. The trails have viewing blinds and observation decks with information about birds you see. A kiosk at the parking lot lists recent bird sightings, and a bird checklist is available so you can update your bird list. Bring binoculars, spotting scope, and camera.
- Bald eagles, America’s national bird, are often seen at Fossil Creek Reservoir, especially in winter. The eagles roost in tall cottonwood trees near the lake and are seen in the trees, eating fish, and soaring around the area. The best times to see the birds are January and February since they usually leave by mid-March. Late afternoon and early evening are the best times to see them. Fort Collins volunteer naturalists lead birding walks on winter weekends to view the bald eagles.
- The Fossil Creek Reservoir Natural Area offers several trails for hikers and birders. The 0.25-mile paved Heron Loop Trail leads to a wildlife blind. The trail is handicapped accessible. The 0.4-mile Sandpiper Trail leads to a viewing area. It’s closed from March 1 to June 15 for waterfowl nesting. The unpaved 1.2-mile Cattail Flats Trail makes a loop on the south side of the lake. It’s closed in winter for roosting bald eagles. The one-mile Carpenter Road Trail crosses prairie on the south side of the natural area to Duck Lake.
- The natural area, open daily from dawn to dusk, has a visitor center and picnic tables and shelters. Dogs and bicycles are prohibited.
Recommended season(s): Year-round.
—Stewart M. Green