Harrison Reservoir is one of a chain of lakes and reservoirs whose presence facilitate the movement of waterfowl, shorebirds and other migrants from the Rocky Mountain Front through the semi-arid mountain valleys of west central Montana. This 628 hectare reservoir attracts an exceptional diversity and, at times, large concentrations of waterfowl and shorebirds. Approximately three quarters of the reservoir is surrounded by short grass prairie, with the northern shore comprised of juniper and limber pine breaks. A small percentage of the lake's margin near the inlets of three different creeks support willow and cattail marshes.

Ornithological Summary

Over 155 species of birds have been documented in the Harrison Reservoir IBA area; they include 30 species of waterfowl, 3 species of loon, 6 species of grebe, 12 species of raptors, 29 species of shorebirds, and 12 species of gulls and terns. Of these birds, 27 of these species are of conservation priority, with at least 23 of those using the IBA area on an annual basis.

This reservoir is an important migration stopover area during spring and fall for a multitude of waterfowl (ducks, geese, and swans) and for shorebirds during both spring and fall.

Additionally, there are grassland birds nesting along the lake margins and adjacent lands. Long-billed Curlews are known to nest just outside the IBA boundary, with the young of the year staging at the reservoir in August. Finally, singing Grasshopper Sparrows and Willow Flycatchers indicate breeding by these songbirds.

Surveys have been conducted by John Parker and friends since 1993, with intensive sampling in the years 2007, 2008 and 2009 (primarily fall surveys).


The data included herein were collected by John Parker, with major assistance from Mark Donahue, Robin Wolcott, Ed Harper, Lou Ann Harris. Approximately 85% of the surveys were conducted in the fall, with most of the remainder occurring in spring.

John Parker possesses detailed spread sheets of birds recorded. Here we report high counts of individual species.

In order to establish the ornithological significance of Harrison Reservoir, John and friends surveyed extensively in 2007 (15 visits), 2008 (13 visits) and 2009 (15 visits). A number of trips were also conducted in 2006 and 2010. In the 15 years prior to these extensive efforts, John conducted approximately 50 trips recording high numbers of individual bird species. For the years prior to these he researched notable birds of Harrison Reservoir via North American Birds (field notes) and utilized P.D. Skaar?s Montana Bird Distribution to glean important recordings.

Conservation Issues

Boating, water-skiing, and jet-skiing can all impact waterfowl and shorebirds. Generally however, these occur during the summer and are not as prevalent during the fall or spring (when the lake is used for as a migration stop-over area, and disturbance might push the birds out). Additionally, with current lake levels, boats generally do not access the southern end of the lake where the wetland habitat occurs. If levels were to rise, access would likely increase.

Hunting pressures exist but are currently managed appropriately.

The most significant threat may be a wind farm development proposed for an area just south of the reservoir, the area where birds funnel into or out of the lake during migration (presently proposed within 1 to 2 miles). Although there is no guarantee this proposal will move forward, feasibility studies have been completed, and we will work to obtain any data they are willing to share and recommend mitigation or provide other comments as appropriate.


This IBA is comprised primarily of Harrison Reservoir (also known as Willow Creek Reservoir) and includes a public fishing access (administered by Montana Fish Wildlife and Parks). The water is managed by a local water district for area irrigation. The rest of the lakeshore and the lands surrounding the reservoir are privately owned, with app. 5% in conservation easements.

The 75% State/Other refers to the water in the reservoir.


The wetlands are located on the south end of the reservoir (consisting of emergent cattails and willows) and the amount of exposure varies as the reservoir levels are altered. There are three small feeder streams. Approximately 75% of the upland is pastureland and presently cattle are well-managed and rotated frequently.

At the shore line lands are not cultivated; it is primarily pasture with varying amounts of grazing. No fences restrict cattle at this time.

Land Use

The water in the reservoir is managed by the local water district primarily for irrigation.

Much of the land surrounding the lake is pastureland used for grazing. There are approximately four private land owners (ranches) that encompass the boundaries of the IBA, with one owner holding about 75% of the dry land. One landowner has entered a portion in a conservation easement (North shore, 5%).

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