- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
Regular breeding resident and migrant; occasionally a late migrant will linger in the state through the early winter months. The Great Egret was an uncommon species during the Minnesota Breeding Bird Atlas (MNBBA).
The Great Egret is largely restricted to the southern United States, with year-round populations found in the southeastern states, California, the Caribbean Islands, and along the coasts of Central America and the west coast of South America. Small populations are present throughout the upper Mississippi River valley and central states, in southern Manitoba, Ontario, and Quebec, and in the Pacific Northwest. The egret reaches its highest breeding densities in the lower Mississippi River valley (Figure 1).
Assigned a Continental Concern Score of 7/20 by Partners in Flight and designated a species Not Currently at Risk by the North American Waterbird Conservation Plan.
A year-round resident to medium-distance migrant; the distance travelled south by northern populations may vary from year to year.
Small fish, aquatic invertebrates, amphibians, reptiles, small mammals, and birds.
Usually a stick platform on tall trees and shrubs; occasionally nests on the ground. A colonial nesting species.
Prior to the species’ near extinction by plume-hunters in the late 1800s and early 1900s, the Great Egret was not known as a breeding species in Minnesota. Roberts (1932), however, remarks that it was an occasional straggler into the state. Specific records included sightings in Fillmore County in the 1880s by Dr. Hvoslef; records along the Minnesota River above Fort Snelling during the 1880s by Dr. Hatch (1892); and a record of two birds seen at Heron Lake in 1894. Indeed, more than one hundred years ago, biologists already recognized that juvenile egrets had a propensity to disperse northward once they fledged, with peak numbers often observed during the months of August and September (McCrimmon et al. 2011). Roberts (1932) quoted the following from Cooke and Widman’s 1883 book on bird migration in the Mississippi valley regarding the Great Egret: “The greatest wanderers are the young which in the fall often stray northward into regions where the species is not known to breed.”
By the early 1900s, however, population numbers had plummeted and the late summer stragglers were no longer seen in Minnesota. It would take the birth of a national conservation movement to bring plume hunting to an end, and nearly 25 years of recovery, before the Great Egret returned once again to Minnesota.
The first reports of observations were in August of 1937 at several locations: the Bass Ponds in Hennepin County, near a wetland in Fairmont in Martin County, and at Lake Shetek in Murray County (Rysgaard 1937). Late summer reports would continue to accumulate through the years, with numerous reports from scattered locations throughout southern Minnesota in the 1940s and 1950s. Reports from several northern counties were noted in later years, including Carlton County in 1960 (Gullion 1961), Clearwater County in 1968 (Marshall 1969), and Cook County in 1986 (Webb 1986).
It was not long before the first nesting was reported in the summer of 1938 on East Chain Lake in Martin County (Erickson and Upson 1938). Although this report was a secondhand account, a well-documented report of egrets nesting along the Mississippi River near Winona was investigated by Walter Breckenridge the following year. He found three egret pairs nesting in a mixed-species colony with Great Blue Herons, Double-crested Cormorants, and Black-crowned Night-Herons (Breckenridge 1939).
In the years that followed, Green and Janssen (1975) would report nesting in 17 counties south of a line that stretched from Pelican Lake in Grant County east to Anoka and Washington Counties. Included were nesting reports from well-known, mixed-species colonies at Shields Lake in Rice County (Hanlon 1956) and Lake Johanna in Pope County (Tvrdik 1966). Summer reports of birds seen even further north, including in Clearwater, Otter Tail, and Marshall Counties, led the authors to conclude that the birds would continue to expand northward. Just 12 years later, Janssen wrote that nesting had been confirmed in 29 counties since 1970, including Becker, Marshall, and Otter Tail (Janssen 1987).
About the same time, the Minnesota Nongame Wildlife Program of the Minnesota Department of Natural Resources (MNDNR) issued a series of four technical reports that were an effort to assemble a comprehensive inventory of all colonial waterbird nesting sites in the state (Henderson 1977, 1978, 1984; Henderson and Hirsch 1980). The reports were a compilation of reports from MNDNR field staff as well as data gathered by local and federal resource agencies and colleges and universities. Published accounts also were compiled. The combined results were summarized by Guertin and Pfannmuller (1985), who reported a total of 22 active Great Egret colonies in the state distributed across 21 counties located primarily in central, southeastern, and northwestern Minnesota from 1981 to 1983. The birds were entirely absent as a breeding species from southwest, north-central, and northeastern Minnesota.
All Great Egret nesting sites were located within mixed-species colonies; 21 were in association with Great Blue Herons and often included Double-crested Cormorants and Black-crowned Night-Herons. A colony that was active for many years on Lake of the Isles was the only site where Great Egrets did not nest with Great Blue Herons but instead nested within a colony of Black-crowned Night-Herons. Of the 22 colonies, 17 supported 50 or fewer Great Egret nests; 3 sites supported 51–200 nests; and 2 sites supported 501–1,000 nests. The 2 largest colonies were on Long Lake in Kandiyohi County (860 nests in 1981) and Egret Island on Pelican Lake in Grant County (743 nests in 1981).
Several years later, Hertzel and Janssen (1998) identified 29 counties where nesting records had been confirmed since 1970. The majority of counties remained in southeastern, central, and northwestern Minnesota.
MNBBA participants reported 815 Great Egret records in 10.2% (483/4,744) of the atlas blocks that were surveyed and in 11.8% (276/2,337) of the priority blocks. Breeding evidence was reported in less than 1% (24) of the surveyed blocks. Two of these blocks actually represented just one breeding locality: Egret Island on Pelican Lake (Figures 2 and 3; Table 1). The birds were reported in 54 of Minnesota’s 87 counties and were confirmed breeding in 19 counties. Two colony sites along rivers were in blocks that straddled multiple counties (the Marsh Lake colony on the Minnesota River and the Pig’s Eye Island colony on the Mississippi River). Colonies were restricted primarily to the central region of the state; none were located north of Becker County. Four breeding counties reported by the MNBBA were additions to Hertzel and Janssen’s 1998 list: Becker, Carver, Lincoln, and Renville. Unlike surveys conducted in the 1980s, several of the colonies where Great Egrets nested did not include Great Blue Herons
Although MNBBA participants originally reported more probable and possible records than are displayed in Figure 3, the vast majority of those records were changed to observed unless documentation supported other breeding evidence codes. Great Egrets can travel far from the breeding colony to their primary foraging territories. Collectively, several studies have reported that the mean distance traveled from the colony site ranges from about 3 km to 12 km (McCrimmon et al. 2011). One study along the Mississippi River reported an average foraging distance of 8.4 km; a study at the Peltier colony in Anoka reported an average foraging distance of 13.5 km (Thompson 1978; Custer and Galli 2002). As a result, unless birds are seen on the nest, other observations cannot reasonably be assumed to indicate possible or probable breeding status in the locality where the birds were observed.
Notable among the atlas results was the report of only one egret colony (Dakota County) along the entire lower Mississippi River, from the Twin Cities south. This may represent a decline in egret colonies along this stretch of the river and/or their inaccessibility to atlas observers. There was evidence of an earlier decline between 1977 and 1988. The number of Great Egret nests along the portion of the Upper Mississippi River National Wildlife and Fish Refuge that borders Minnesota and adjacent waters in Wisconsin declined nearly 50%, from 466 nests in 4 colonies to 276 nests in 6 colonies (Sauer 1991). Yet many of these sites are in backwater sloughs that are difficult to observe and access. Unfortunately no systematic survey of waterbird colonies along the river is regularly conducted, so their current status in this region is unknown.
The MNBBA does provide a reasonable dataset to compare with the compilation prepared by Guertin and Pfannmuller in 1985 to assess changes that may have occurred in the intervening years. The MNBBA data shows that the Great Egret had a nearly identical distribution during the atlas as it did in the 1980s. Guertin and Pfannmuller (1985) reported 22 active colonies that were distributed across 21 counties; the atlas documented 23 breeding localities distributed across 17 counties.
Elsewhere within its breeding range, the Great Egret’s population range has expanded in some areas. Originally decimated by plume hunting over a century ago, the population quickly recovered and the species reoccupied portions of its former breeding range once it was afforded protection through the Migratory Bird Treaty Act. Beginning in the latter half of the twentieth century, the egret expanded further north in New England, the Great Lakes (including Minnesota), and central Canada, and west in Idaho and Oregon (McCrimmon et al. 2011).
*Note that the definition of confirmed nesting of a species is different for Breeding Bird Atlas projects, including the definition used by the Minnesota Breeding Bird Atlas, compared with a more restrictive definition used by the Minnesota Ornithologists’ Union. For details see the Data Methods Section.