Union Reservoir

Colorado · Rocky Mountains

Habitat
Lake
Best Seasons
SummerFall
Difficulty

Moderate

Best Months

June-October

About This Location

Union Reservoir is a productive birding destination in Colorado, with 281 species recorded on eBird. This lake habitat attracts American White Pelican, Canada Goose, and Mallard among many others. Elevation changes create diverse habitats, from riparian valleys to alpine meadows, supporting a wide range of species.

Location

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Notable Species

Live Bird Data

Powered by eBird / Cornell Lab of Ornithology

Notable Sightings

Rare or unusual species spotted nearby in the last 14 days

American Barn Owl

Tyto furcata

3/5/2026High Plains Environmental Center1 observed

Blue-winged Teal

Spatula discors

3/5/2026Walden Ponds Wildlife Habitat--Walden & Sawhill Ponds all together3 observed

Acorn Woodpecker

Melanerpes formicivorus

3/5/2026Mountain View Cemetery (Boulder Co.)1 observed

Barn Swallow

Hirundo rustica

3/5/2026Walden Ponds Wildlife Habitat--Walden & Sawhill Ponds all together2 observed

Winter Wren

Troglodytes hiemalis

3/5/2026Plaster Reservoir1 observed

Yellow-bellied Sapsucker

Sphyrapicus varius

3/4/2026Mountain View Cemetery (Boulder Co.)1 observed

Western Bluebird

Sialia mexicana

3/4/2026University of Colorado Boulder--South Campus1 observed

Recent Observations

Species reported at this location in the last 14 days

American White Pelican

133/5/2026

Canada Goose

83/3/2026

Mallard

43/3/2026

Killdeer

13/3/2026

Bald Eagle

13/3/2026

Common Raven

13/3/2026

Cackling Goose

13/2/2026

Gadwall

373/2/2026

American Wigeon

33/2/2026

Eurasian Collared-Dove

33/2/2026

Ring-billed Gull

373/2/2026

Song Sparrow

53/2/2026

Northern Shoveler

22/27/2026

Bufflehead

22/27/2026

Common Merganser

852/27/2026

American Coot

12/27/2026

Western Meadowlark

12/27/2026

Snow Goose

12/26/2026

Green-winged Teal

62/26/2026

Redhead

302/26/2026

Birding Tips

  1. 1

    Scan the water surface methodically for diving ducks, loons, and grebes.

  2. 2

    Check the shoreline and mudflats for shorebirds and wading birds.

  3. 3

    Acclimate to altitude before hiking to high-elevation birding spots.

Frequently Asked Questions

When is the best time to visit Union Reservoir for birding?
The best months to visit Union Reservoir for birding are June-October. The best seasons are Summer and Fall.
What birds can I see at Union Reservoir?
Notable species at Union Reservoir include American White Pelican, Canada Goose, Mallard, Killdeer, Bald Eagle. The area supports lake habitats.
How difficult is birding at Union Reservoir?
Birding at Union Reservoir is rated as Moderate. Some trails may require moderate fitness and basic hiking ability.
What amenities are available at Union Reservoir?
Union Reservoir offers the following amenities: Parking, Trails.