Northern Prairie Wildlife Research Center
Foremost among the published sources of data on bird occurrence and distribution presented in this report were the Loon and its predecessor, the Flicker, the quarterly publication of the Minnesota Ornithologists Union, and the Passenger Pigeon, the quarterly publication of the Wisconsin Society for Ornithology. Important papers dealing with species or species groups have been published in these journals and extensive use was made of the data contained therein. Considerable use was made of published reports in American Birds, the field report publication of the National Audubon Society. Probably the most important contribution of American Birds to the present report was the yearly publication of Christmas Bird Counts (CBC) conducted in both States.
I conducted field work in this region from 1966 through 1978, and intermittently during 1979-80. Before 1969, most observations were made in northern Polk, southern Douglas, Burnett, and eastern Pine counties. During 1969-76, field work was expanded to include the remainder of the counties and intensive observations were started on several species in Pierce, St. Croix, and Washington counties. Many of the dates of occurrence and statements on abundance and distribution were derived largely from my unpublished field notes. The unpublished field notes of Rev. Samuel Robbins for 1960-68 in St. Croix, Polk, and Pierce counties were also examined extensively. Several State parks and wildlife management areas in both States were visited and some limited data (with the exception of the Crex Meadows Wildlife Area) were made available.
Data on breeding and winter status were gathered from three sources. First, intensive field work by several previous investigators and me led to the discovery of numerous nests or dependent young. These observations provide the foundation for species status remarks and habitat use of breeding birds. Secondly, the U.S. Fish and Wildlife Service, Migratory Bird and Habitat Research Laboratory, Laurel, Maryland, has established a number of BBS transects throughout North America (Robbing and Van Velzen 1967). These 39.2-km transect routes are selected at random and are censused once each year during June. Five transect routes were established in the Valley; unfortunately, all five are in Wisconsin (Fig. 4). Data from these routes are presented to point out regions of peak populations of several species and, in some instances, to show geographic differences in species breeding distribution. Third, CBC sponsored by the National Audubon Society provide an important source of data on winter bird populations and geographic differences in species abundance. At least eight CBC areas have been established within the Valley. However, only five (Fig. 5) have been counted for a sufficient number of years to allow meaningful comparisons.
Fig. 4. Location of Breeding Bird Survey routes in the St. Croix River Valley.
Fig. 5. Location of major Christmas Bird Count areas in the St. Croix River Valley.
Considerable conjecture and argument has developed about what is the best method for describing a species occurrence, regularity, and abundance. Terms are treated under three categories: status, season, and abundance. The terms used to describe each species status in the present report are adapted from those presented in Green and Janssen (1975), including
Regular - A species that occurs at some location in the Valley during at least one season each year.
Casual - A species expected to occur at least once every 3 to 5 years, but not annually.
Accidental - A species that is not expected to occur again or that occurs very infrequently.
Hypothetical - A species that probably occurred in the Valley at least once, but the circumstances of the observation leave the record in doubt.
Introduced - A species that is naturally foreign to this region but has been released in the area as an act of man and is now established and reproducing without additional influence by man.
Extirpated - A species that once occurred naturally in the Valley, has now been eliminated, but still exists elsewhere. This term applies to both migrants and nesting species.
Extinct - A species that no longer exists anywhere on earth.
The population status of several species has recently become a concern of the public. Legal protection for all birds except the rock dove, starling, and house sparrow has been provided by the Federal Government by the Migratory Bird Treaty Act of 1918, as amended (40 Stat. 755; 16 U.S.C. 703-711). Eagles have been afforded additional protection by the Eagle Act of 1940 (54 Stat. 250; 16 U.S.C. 668). Several species have been given even greater protection by the Federal Endangered Species Act of 1973 (87 Stat. 884; 16 U.S.C. 668aa-668cc). Both Minnesota and Wisconsin have enacted special legislation within their respective States that provides statewide protection for species that are declining locally or regionally, but not on a level to be afforded protection by the Endangered Species Act of 1973.
Official lists of protected bird species have been prepared for Minnesota and Wisconsin. Forty-three of the species listed by either State have been recorded in the Valley (Table 1). Terms used throughout this report to describe the special status of these species are adapted from Les (1979) and Moyle (1980).
Endangered - A species whose continued existence is in jeopardy and is provided special protection by law.
Threatened - A species that appears likely to become endangered. Threatened species are provided special protection by law.
Watch - A species for which some problem of abundance is suspected but not proven. The purpose of this classification is to focus attention on a species before it becomes threatened or endangered. This is an informal classification and no additional legal protection is provided. In Minnesota, species in this classification are considered Priority.
Terms used in describing the occurrence of a species in the Valley include
Permanent resident - A species that is largely nonmigratory or, if rnigratory, only a very small proportion of the population departs during a migration period.
Migrant - A species that normally occurs in the Valley only during the well-defined spring and fall migration period.
Nesting species - A species for which a viable clutch of eggs, dependent young in the nest, or young that have left the nest but are still dependent have been observed.
Summer resident - A species that occurs in the Valley during the normal nesting period and in all likelihood nests, but for which there are no confirmed records of eggs or dependent young.
Winter resident - A species that winters even though greater numbers may occur during migration.
Terms used in relating the relative abundance of each species during migration, winter, or the breeding season relate to its importance to the total avifauna. These terms adapted from Stewart (1975) are described as follows:
Abundant - A species that, because of its habits and conspicuousness occurs in very large numbers.
Common - A species that occurs in large numbers.
Fairly common - A species that occurs in fair to moderate numbers.
Uncommon - A species that is found in low numbers.
Rare - A species whose range includes the Valley but is recorded in low numbers.
Very rare - A species that occurs in such low numbers that it is of minor importance.
|Wetland name used in this report||Wetland type (Shaw and Fredine 1956)||Water Chemistry||Authority|
|Temporarily flooded||Cowardin et al.|
|Northern sedge meadow||Curtis|
|Seasonally flooded||Cowardin et al.|
|Semipermanently flooded||Cowardin et al.|
|Permanently flooded||Cowardin et al.|
The taxonomic treatment of birds presented in this report follows the American Ornithologists' Union (AOU) Check-list of North American Birds (1957), and the 32nd (AOU 1973) and 33rd (AOU 1976) supplements to the Check-list. One deviation from the AOU standard sequence is presented for the shorebirds. In this instance, I followed the sequence recommended by Jehl (1968).
Description of the major plant communities of the Valley follows Curtis (1959). Major habitats used by each species were determined from personal field investigations and from published reports. The taxonomic names of plants described in the habitat sections are those used in Gleason and Cronquist (1956). Common names of some plant species, primarily grasses and sedges, are taken from Britton and Brown (1913). Voucher specimens of most of the important grasses and forbs used in this report are housed in the Herbarium, Department of Biology, University of Wisconsin-River Falls.
The wetland classification used in this report (Table 2) is a combination of the systems developed by Cowardin et al. (1979) and Curtis (1959). Cowardin et al. (1979) employ a hierarchical system with modifiers for water regime, water chemistry, and soil type. Three wetland types (Northern Sedge Meadow, Shrub Carr, and Bogs) were named and classified by Curtis (1959). Because these names are widely used and accepted in the Valley, I have deviated from Cowardin's system in that instance.