The Avon Hills are a series of heavily-forested glacial moraines, kettle holes, and small to medium-sized lakes and small marshes that run from west of the St. Wendel bog in St. Joseph Township, Stearns County and from Pelican Lake near the town of St. Anna in Avon Township southwestward to eastern Farming Township and encompassing most of Collegeville Township south to near Cold Spring. Prominent features include hills as high as 1,417 feet, the large tamarack-rimmed St. Wendel Bog which includes Swamp Lake, the St. John??s Arboretum (2,737 acres) which includes the St. John??s University campus, three waterfowl production areas in Collegeville Township, and two state scientific and natural areas (Max Partch Woods in St. Joseph Township and the Avon Hills Forest SNA in two areas of Avon Township). Notable lakes in the boundary include Kraemer Lake in St. Joseph Township, Big Fish Lake, Big Watab Lake, and Lake Sagatagan in Collegeville Township, and Pelican Lake, and the three lakes of the Spunk Lake Chain in Avon Township. Interstate 94 runs northwestward through the middle of this area. The largest towns in these townships are St. Joseph and Avon, but urban sprawl from St. Cloud is creeping westward across St. Joseph Township.
Most of the forested hills are characterized by a mixture of hornbeam, maples, basswood, oaks, and ash with scattered aspen and birch stands. Lowland forests are dominated by sugar maple, young elm, ash, and in some areas tamarack. On the St. John??s Arboretum lands there are also stands of mixed conifer species and some areas where naturalizing conifers have created a mixed forest situation. A large restored prairie of some 100+ acres exists on the northwest side of the Arboretum. Numerous small sedge and cattail marshes ring the wetlands in the area.
The Avon Hills represent the largest, relatively intact block of kettle and moraine forested landscape remaining between the Twin Cities and Morrison County (Camp Ripley IBA). Historically, it was the site of the only known Stearns County nest of the Passenger Pigeon (1881) and the second to last breeding record of the Swallow-tailed Kite (1904) in the entire Midwest. In recent decades this area has been an important foothold in central Minnesota for northward-moving species such as Red-shouldered Hawk, Blue-gray Gnatcatcher, Northern Cardinal, Wood Thrush and Red-bellied Woodpecker, all of which are now well-established.
Scattered records of Blue-winged Warbler and Prairie Warbler hint at possible breeding and future establishment of these species. The Red-shouldered Hawk population is widespread within the IBA, and is as common here as any place in the state with the possible exception of Camp Ripley IBA. Other southern birds that occurr here but which have not yet established a breeding foothold include the Yellow-crowned Night Heron, Prothonotary Warbler, Louisiana Water-thrush, and Hooded Warbler.
The area has a very large breeding Wood Duck population due perhaps to the forested kettle landscape. Fall concentrations have totaled 400 birds on just one remote Collegeville Township bog. Several waterfowl production areas produce many pairs of Mallard, Blue-winged Teal, Wood Duck, Hooded Merganser, Pied-billed Grebe, and a few Red-necked Grebes.
The Common Loon population is quite dense with an estimated 25-30 pairs and probably acts as a source population for loons elsewhere in Stearns County. Since many of these lakes are for non-motorized travel or are too shallow for much recreational activity, loons appear to be thriving. Both Collegeville (2005) and Avon Townships (Linneman Lake in 1937, 1942, 1976) also have had periodic breeding of the Common Moorhen. More thorough searching might prove this species as regular. Forster??s Terns occur commonly in migration with 120 counted at Gimini Lakes on 14 May 1966 and several dozen seen at the same site in 2005.
The Cerulean Warbler population, while diminished from its peak numbers back in the 1960??s, due perhaps to loss of mature American elms, is still recognized as a significant population by the Cornell University Cerulean Warbler Atlas Project, and may represent the largest concentration on the northwest edge of its North American range which is gradually expanding northward. As a key potential source population for any northwest breeding expansion, this population may prove quite invaluable in the future. Collegeville Township, due to its many acres of planted conifers and large expanse of unbroken hardwood forest, has proved to be arguably the finest winter forest birding site in the central portion of the state south of the boreal forest. Both Red-breasted Nuthatch and Purple Finch have had small, well-established breeding populations here that have persisted at least since the 1960??s. These represent the most southwesterly established populations east of the Great Plains and in Minnesota. Many winter season rarities have occurred in these conifers including multiple Gray Jays, Black-backed Woodpecker, Northern Goshawk, Clark??s Nutcracker, both crossbills (spring and summer records for Red Crossbill may indicate occasional breeding), Pine Grosbeak, and Hoary Redpoll. A small Long-eared Owl breeding population occurred here as recently as the early 1990??s and may still persist.
The large St. Wendel tamarack bog has a unique northern bird assemblage including breeding Ring-necked Duck, Veery, Dark-eyed Junco, Mourning Warbler, and Nashville Warbler (most are at or near their southern or southwestern limits in the state) and may harbor other such species on occasion. Both Willow and Alder Flycatchers reside here with the two species sorting out their breeding habitats in different sections of the bog.
The area, particularly Collegeville Township, has a long history of ornithological surveys that extend as far back as T.S. Roberts?? railroad surveys in the Sauk River area and Reverend Severin Gertkin at St. John??s University in the 1800??s, Professor Ed Hibbard in the 1950-1960 period, Nestor Himenz from 1940-1960??s, Kim Eckert and Bob Russell in the 1960??s and later, Professor Norm Ford in the 1960??s to the 1980??s, and Dr. Phil Chu, Bob Rogers, Herb Dingman, and Reverend Bruce Wollberding in the 1990??s and continuing today. Field notes, articles, and observations by these observers have produced a body of landscape data that is invaluable for studying the distribution and historical changes of birds in this part of Central Minnesota and may be unprecedented anywhere in the state for longevity. The area is widely utilized by students from the three area universities and also encompasses the western half of a Christmas Bird Count circle that dates back to the mid-1960s.
The Avon Hills have attracted a number of cell towers and radio towers. Periodic checking of the radio towers has found only small numbers of dead birds. The area has a potential for wind turbine development as well. Extraction industry is limited to gravel quarries but more may be built to support St. Cloud development. Urbanization is the greatest threat to the area from St. Cloud sprawl and lakeside development. The urbanization threat is greatest in St. Joseph Townships but all townships are vulnerable.
Deer grazing is a serious threat to the current and future composition of the area??s forests. Managers at St. John??s Arboretum have fenced young oaks and done extensive oak plantings to minimize this threat but the threat extends to all lands in the region. Forest succession is related to this issue. Several early success ional species have disappeared from the Avon Hills as forests have mature including breeding Eastern Towhee and Golden-winged Warbler. Ruffed Grouse numbers have also declined so that the species is now rare. The sustainable forestry practices at St. John??s have generally preserved the forest canopy which has helped birds favoring large forest tracts, but have not created large patches of early success ional habitats attractive to birds like towhees and woodcock.
Lake home development has largely built out the available shorelines in the region. Loon breeding seems to be compatible with the existing home density currently but the effects on Red-necked Grebes, moorhens, bitterns, and other waterbirds are unknown.
The Avon Hills are a series of heavily-forested glacial moraines, kettle holes, and small to medium-sized lakes and small marshes that run from west of the St. Wendel bog in St. Joseph Township, Stearns County and from Pelican Lake near the town of St. Anna in Avon Township southwestward to eastern Farming Township and encompassing most of Collegeville Township south to near Cold Spring. Prominent features include hills as high as 1,417 feet, the large tamarack-rimmed St. Wendel Bog which includes Swamp Lake, the St. John??s Arboretum (2,737 acres) which includes the St. John??s University campus, three waterfowl production areas in Collegeville Township, and two state scientific and natural areas (Max Partch Woods in St. Joseph Township and the Avon Hills Forest SNA in two areas of Avon Township).