Site Details

descriptions and directions

Cottonwood Marsh photo by Peter Burke

Accessible Boulder Reservoir - Boulder County
Aliases: Sixmile Reservoir, Coot Lake
Ownership: None Listed
Description: This City of Boulder park charges an entrance fee during the summer, but not during the winter. This is fortuitous for birders, as the colder months are definitely the better ones for birding here. Being the largest body of water in the county, Boulder Reservoir attracts rare waterbirds at a high rate. Loons, grebes and diving ducks are a good bet in migration, and jaegers and rare gulls and terns have shown up on occasion. Ospreys breed along the west shore, which is seasonally closed for that reason. From the east end of the entrance road, if you so desire, you can walk the dam north to get better views of distant birds. The main entrance road runs along the south shore of Boulder Reservoir and the north shore of the smaller Sixmile Reservoir, which can also be excellent for birds. For alternate access to Boulder Reservoir, you can park at one of the other parking lots, which will get you out of paying the entrance fee. One is in the northwest corner of the reservoir along 51st Street, and the other is in the northeast corner along 75th Street. Both require you to walk a quarter to a half mile in order to scan the water. The northeast parking lot is adjacent to Coot Lake, which can host marsh birds like rails, American Bittern, and roosting blackbirds, in addition to its namesake.

Habitat: Pond/Lake/Reservoir
Directions: From Boulder, head northeast on the Diagonal Highway (CO 119) to Jay Road and turn left (west). Once on Jay, take an almost immediate right (north) just past the fire station onto 51st Street, which is signed for Boulder Reservoir. The main entrance is on the right in a little over a mile. To get to the northwest corner of the reservoir, continue on 51st Street another mile past the main entrance. To get to the northeast corner of the reservoir, instead of exiting the Diagonal at Jay Road, continue on it to 63rd Street and take a left (north). The parking lot for Coot Lake is on the left side of the road in about a mile.
Other Wildlife:
Other Attractions:

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Other Sites in Boulder County
eBird Seasonal Bar Chart

Latest Boulder Reservoir Sightings from eBird


CBRC Records from Boulder Reservoir

SpeciesAccession No.Date(s)
Tundra Swan2003-13111/13/2003
Mexican Duck2011-47 5/12/2011
Ruff2008-42 5/1/2008
Red Phalarope2005-108 10/12/2005
Red Phalarope2011-127 9/19/2011
Long-tailed Jaeger2007-88 9/13/2007
Long-tailed Jaeger2014-142 09/19/2014
Iceland Gull2015-003 12/01/2014
Arctic Tern2011-146 10/18/2011 - 10/29/2011
Arctic Tern2015-121 11/11/2015
Snowy Owl2018-031 01/20/2018