Lake Byllesby lies in the Cannon River Valley located about 30 miles due south of downtown St. Paul along the south border of Dakota County and the northwest border of Goodhue County. The lake essentially is bisected throughout its length by the two adjacent counties. It sits between the municipalities of Cannon Falls near the east end and Randoph near the west end. The IBA is bounded by Hwy. 56 on the west, Co. Rd. 88 on the north, the eastern boundary of Lake Byllesby Regional Park on the east and the shore of the lake on the south. This boundary includes the lake and the county owned and managed Regional Park and adjacent lands on the north.
From St. Paul, take Hi 55 south to where it joins Hi 52. Take Hi 52 south to the Hampton exit. Follow CR 56 south to CR 88. The west end of Lake Byllesby is just southeast of this intersection.
Lake Byllesby is an impounded lake resulting from damming the Cannon River in 1910 just above the town of Cannon Falls (1). At approximately 580 ha (1,435 acres), it is the largest lake away from the Mississippi and Minnesota River corridors in each of the two counties and is also the largest "inland" lake in the ten contiguous counties comprising the southeast corner of Minnesota. The lake is shallow, averaging 11.6 ft. (1) throughout becoming most shallow at the far west end where the Cannon River enters the lake. At this location, extensive alluvial mudflats are exposed when lake levels are lowered. The lake is owned by the Minnesota Department of Natural Resources and is managed through a cooperative agreement with North American Hydro. The current management plan requires the lake level to be lowered each spring to minimize groundwater impacts on the planting of crops on adjacent farm lands. This level is maintained until May 15 at which time the level is allowed to rise to a summer pool level of 856.7 ft. above msl. In most years, this lowered level results in exposing extensive alluvial mudflats and adjacent shallow water areas that are preferred habitat for an impressive diversity of migratory bird species including shorebirds, ducks, geese, swans, herons, pelicans, gulls, and terns. Shorebirds annually are represented at Lake Byllesby in numbers and diversity of species not found elsewhere in eastern Minnesota.
Land ownership is a mix of private and public. The principal public landowner on the Dakota County side of the lake is Dakota County, Department of Parks and Recreation, and consists of Lake Byllesby Regional Park. The principal adjacent landowner on the Goodhue side of the lake is Goodhue County. The remainder of the adjacent land is in private ownership.
As birds migrate northward in the spring via the Mississippi River corridor, many eventually leave the corridor and head northwest across southeast Minnesota to follow the prairie-hardwood transition zone enroute to their breeding grounds to the north. The relatively large size of Lake Byllesby with its associated extensive mudflats and shallow areas provide important resting and feeding habitat that is in very short supply in this region of the state. The site contains an assemblage of species characteristic of shallow wetland and alluvial mudflat habitat type. This includes: 31 (78%) of Minnesota's 40 recorded shorebird species; 30 (70%) of Minnesota's 43 recorded waterfowl species; Common, Forster's, Caspian, and Black Tern; American White Pelican, and others.
Shorebirds especially seek out the insect larvae that thrive in the mudflats and shallow water that occurs during partial drawdown periods. This high protein food resource is especially critical for females in preparation for egg laying soon after arriving on the breeding grounds. Partial draw-downs occur annually in the spring as per a prescribed water management plan, but occasionally occur to a lesser degree in the fall providing benefits to southbound migratory birds as well. Availability of important food resources during migration is critical to ensure these birds arrive in good condition on the breeding grounds and/or on the wintering areas.
In recent years, Lake Byllesby has become increasingly popular among birders as an excellent place to view shorebirds and myriad other water birds during migration. For example, on March 11, 2006 birders counted as many as 1500 Greater White-fronted Geese using the lake along with some 20 other species of waterfowl. White-fronted Geese are normally uncommon in eastern Minnesota. Lake Byllesby has become one of the most reliable lakes in Minnesota where the federally endangered Piping Plover can be found in migration. It has been recorded nearly annually during the last 10 years, usually singly, but 2 birds (one banded) were found May 7, 2002. State threatened Wilson's Phalarope and Common Tern are recorded in low numbers annually. Several hundred American White Pelican (e.g. 450 - April 15, 2004) are recorded each spring loafing and feeding near the mudflats. A pair of Bald Eagles nest just west of the lake along the Cannon River and uses the lake for feeding and perching on a regular basis.
Canvasbacks typically stage at Lake Byllesby during spring migration. As many as 1200 (April 5, 2004) have been recorded with several hundred being the norm. This is probably the largest concentration of this species in the eastern portion of Minnesota away from the major rivers. Lesser Scaup, a declining diving duck species of growing concern continentally, occurs in the hundreds annually, as do Redhead and Ring-necked Duck. Northern Pintail and American Black Ducks also occur annually. American Avocet has become almost annual with as many as 9 individuals documented May 19, 2004. Both Marbled and Hudsonian Godwits occur in low numbers annually.
MN-1b) Shorebirds: During spring migration each year the site supports shorebirds in excess of 4000 individuals, some years far more than that. The numbers would no doubt be even greater but the current management plan calls for raising the lake level beginning May 15. This quickly inundates the mudflats and essentially makes the area unsuitable for most shorebirds. Shorebird migration typically extends until the end of May and into early June.
MN-1e) Species diversity: At least 31 species of shorebirds have been documented at Lake Byllesby and, on average, about 25 species occur annually. Single day totals of 20 or more species have been documented on more than one occasion. (e.g. May 17, 2004; May 10, 2003, J. Mattsson, Drew Smith personal records). Thirty species of waterfowl have been documented with about 26 species occurring regularly. Each of Minnesota's 6 grebe species have been recorded.
Water management: Potentially, the most serious threat that would reduce the quality of the site for migratory shorebirds and other water birds is deviation from the current spring protocol, i.e. summer pool level reached prior to May 15. High water levels in the spring essentially eliminate shallow habitat required by these species.
The following excerpt is taken from MPCA 1996 Lake Assessment Program, Byllesby Reservoir (I.D. #19-0006):
"The flow through Byllesby Reservoir dam is highly regulated. The operator of the dam (North American Hydro) is required to maintain ?instantaneous? flow through the dam so precipitation events are passed downstream with only minor increases in reservoir volume. The hydro-power producer is also required to submit hourly reservoir level and flow information to the Minnesota Department of Natural Resources. The pool (lake) elevation is maintained at 856.7 feet above mean sea level. In general, the pool level does not usually fluctuate by more than two feet over the course of the summer. Fairly typical lake level fluctuations were apparently the case for 1996. Historic lake levels, however, have fluctuated considerably when dam repairs or other operation and maintenance activities were necessary." Disturbance: During the spring migration period, human disturbance is usually minimal because few boaters use the lake due to low water levels. This is especially true in the far west end of the lake where extensive shallow conditions prevail. However, as water levels rise, boating increases and so does disturbance to birds. In fall, waterfowl hunting occurs along the south shore of the main lake and on the islands at the far west end of the lake. Shorebirds and other waterbirds, including ducks and geese, generally avoid the shallow areas near hunting blinds when hunters are present.