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Birds of St. Croix River Valley: Minnesota and Wisconsin

FAMILY ARDEIDAE

Herons and Bitterns


Great Blue Heron -- Green Heron -- Little Blue Heron -- Cattle Egret -- Great Egret -- Snowy Egret -- Louisiana Heron -- Black-crowned Night Heron -- Yellow-crowned Night Heron -- Least Bittern -- American Bittern

Great Blue Heron (Ardea herodias)

Status: Regular migrant and nesting species, casual winter resident.

Migration: Common migrant in the Western Upland and Central Plain, uncommon and local in the Northern Highland. Spring migrants arrive in the Western Upland about 10 March (earliest-1 March 1969, St. Croix County) and reach the Northern Highland by 1 April. Peak migration occurs 5-20 April. Fall migration begins in mid-July with the gradual dispersal of young from rookeries. Peak fall migration occurs 25 August to 30 September and most depart by 10 November (latest-20 November 1964 and 9 December 1971, Burnett County).

Nesting Season Distribution: Fairly common and local nesting species throughout the Valley. Evidence of nesting has been documented in all counties except Pierce. The two largest rookeries in the region are at Crex Meadows Wildlife Area, Burnett County, and at Pine Lake, Pine County. At least four rookeries were active in Burnett County in the late 1940's and early 1950's (Williams 1957). The Crex Meadows rookery located on Phantom Lake was first used in 1952 (Williams 1957). Further records related to the breeding population of this rookery follow:

Deterioration of nest platform trees is the primary cause of the rookery decline at Crex Meadows. Attempts at placing artificial nest platforms for great blue herons on the Phantom Lake rookery have been successful in attracting double-crested cormorants. However, the great blue herons have not reestablished to former levels.

Winter: Three winter records exist for St. Croix County: 2 January 1961; 1 January 1971; and 1 January 1972. All birds were recorded on the Afton CBC.

Habitat: Most nesting rookeries in this region exist as small colonies built on dead or dying deciduous trees near natural lakes. The Burnett County colonies are in decaying trees associated with man-made impoundments. As evidenced by the continual changes in colony size and location of breeding populations at Phantom Lake, these temporary habitats are in a constant state of deterioration. In the Western Upland, several small rookeries exist in living green ash and American elm associated with the Lowland Deciduous Forest community. One rookery in the Northern Highland is in living white pine trees close to the St. Croix River in Burnett County.


Green Heron (Butorides striatus)

Status: Regular migrant and nesting species.

Migration: Common migrant in the Western Upland, primarily on the prairie wetlands of St. Croix, Washington, and southern Polk counties. Fairly common in the Central Plain, and uncommon and local in the Northern Highland. Spring migrants begin to arrive during the last week of April (earliest-6 April 1975 and 12 April 1964, Washington County). Average date of first arrival in Burnett County is 10 May, reaching Douglas County by 15 May. Peak spring abundance occurs 5-20 May. Fall migration begins in mid-August with formation of loose flocks. Peak fall movements occur 1-15 September. Green herons depart the Northern Highland by 15 September and the Western Upland by 10 October (latest-27 October 1975 and 9 November 1965, Washington County).

Nesting Season Distribution: Fairly common nesting species in the Western Upland, particularly the prairie wetland region of St. Croix, Washington, and southern Polk counties. Uncommon in the Central Plain, and rare and local in the Northern Highland. Substantial breeding populations occur in the marshes of Glacial Lake Grantsburg in Burnett County. Roberts (1932) cited a June 1919 nest containing three young in Pine County. Documented breeding records exist for all counties in the river valley except Chisago and Douglas. Jackson (1941) failed to record this heron during the 1919 breeding season in northwestern Wisconsin.

Habitat: Breeding green herons utilize a variety of habitats for nesting. In the Western Upland, breeding pairs and nests are typically observed in seasonally, semipermanently, and permanently flooded wetlands, and riverine habitats. In the Central Plain, breeding green herons are found typically in seasonally and semipermanently flooded wetlands, but also occupy Shrub Carr wetlands with a scattering of open water areas.


Little Blue Heron (Florida caerulea)

Status: Accidental, one record.

Record: One adult was seen near Dunroven, Washington County, on 23 April 1962 (Huber 1962). Because of the recent noticeable expansion of this species in the upper Midwest, I would expect this species to be recorded more regularly in the future.


Cattle Egret (Bubulcus ibis)

Status: Casual migrant.

Records: The first cattle egret record for the Valley was obtained in Chisago County on 7 May 1971, when six birds were observed. One was observed in Washington County on 25 April 1977 (Savaloja 1977). In Pierce County a single bird was observed near River Falls on 28 April 1976. At Crex Meadows, Burnett County, groups of four birds each were observed on 24-28 May 1974 and 16 April 1976. J. O. Evrard reported that cattle egrets were present during July 1979 at Crex Meadows (Tessen 1979b).


Great Egret (Casmerodius albus)

Status: Regular migrant and nesting species. The Wisconsin DNR has listed this species as threatened (Les 1979). Wetland drainage, loss of mature nest trees, pesticides, and human disturbance are listed as reasons for the decline.

Migration: Uncommon migrant in the Western Upland, rare and local in the Central Plain. Except in the vicinity of Crex Meadows, Burnett County, this species is rare north of a line extending from Chisago to northeastern St. Croix counties. First spring migrants arrive in the Western Upland 10-15 April (earliest-29 March 1968) and in Burnett County about 20 April. One Polk County record was obtained on 10 April 1970. Fall migration begins in mid-August. Peak fall populations occur 25 August to 10 September and departure by 10 October (latest-30 October 1970 and 31 October 1956, Burnett County).

Nesting Season Distribution: Rare and local nesting species with documented breeding records from Washington, St. Croix, and Burnett counties. Establishment of this bird as a breeding species has been fairly recent. Jackson (1941) failed to observe great egrets during 1919 in northwestern Wisconsin. Roberts (1932) described the great egret as "occasionally a straggler from the south," yet cites no records from the Minnesota counties. The first record for the Valley is provided by King (1949), who reported this species at Prescott, Pierce County, in 1946. Great egrets were first reported at Crex Meadows, Burnett County, in 1948. Later, summer observations ranged from 19 in 1956 to 1 in 1969. Nesting at Crex Meadows was first recorded on 25 June 1975 (Evrard 1975). Since 1975, a small nesting colony has remained on the Fish Lake Wildlife Area, Burnett County. In Washington County, nesting has been established with a colony of undetermined size (Green and Janssen 1975). St. Croix County breeding records were established in 1976 when two young were seen feeding with adults along Ten Mile Creek on 11 July. These birds nested in a small great blue heron colony along the Willow River near New Richmond.

Habitat: Washington and St. Croix county colonies exist in live trees of Lowland Deciduous Forest. Nests as Fish Lake Wildlife Area occur in jack pine trees killed by the rising waters of Grettum Flowage.


Snowy Egret (Egretta thula)

Status: Accidental, one record.

Record: Norman Stone observed a single snowy egret at Crex Meadows, Burnett County, on 4 and 5 May 1959 (Stone 1959a).


Louisiana Heron (Hydranassa tricolor)

Status: Accidental, one record.

Record: One Louisiana heron was observed at Crex Meadows, Burnett County, on 7 July 1977 (Tessen 1977).


Black-crowned Night Heron (Nycticorax nycticorax)

Status: Regular migrant and nesting species.

Migration: Uncommon and local migrant in the Western Upland, rare in other regions. Spring migrants arrive in the Western Upland 10-15 April, reaching peak abundance 1-10 May. Average date of spring arrival in Burnett County is 10 May. Fall migration begins 25 August to 1 September and departure by 1 October (latest-28 November 1967, Washington County).

Nesting Season Distribution: Rare and local nesting species. Confirmed breeding records have been reported only from St. Croix and Burnett counties; however, several summer observations have been made in Washington County. Roberts (1932) stated that one of the most northerly colonies in Minnesota occurred on the St. Croix River in Pine County. Unfortunately no dates or locations are provided.

Habitat: Three nesting colonies of black-crowned night herons are known in this region. Habitats associated with these colonies include wetland habitat dominated by bulrush and cattail. In proximity are small groves of alder and willow used for nest platforms.


Yellow-crowned Night Heron (Nyctanassa violacea)

Status: Accidental, one record.

Record: Green and Janssen (1975) cite a 6 June 1964 record from St. Croix State Park, Pine County.


Least Bittern (Ixobrychus exilis)

Status: Regular migrant and nesting species.

Migration: Uncommon migrant in the Western Upland and Central Plain. First spring migrants arrive 5-10 May and are most frequently observed 20-25 May. Fall migration begins 15-25 August and departure by 25 September.

Nesting Season Distribution: Uncommon nesting species in the Western Upland, uncommon to rare and local in the Central Plain. Documented breeding records exist for St. Croix County (three nests), Polk County (one nest), and Burnett County (one nest). Summer observations of adults in Chisago and Washington counties provide inferred evidence of nesting in those counties.

Habitat: Principal nesting habitat of the least bittern includes semipermanently and permanently flooded wetlands. Nests observed in St. Croix and Polk counties were in extensive stands of hardstem bulrush and river bulrush. The Burnett County nest was in a mixed stand of cattail and river bulrush.


American Bittern (Botaurus lentiginosus)

Status: Regular migrant and nesting species, accidental in winter.

Migration: Fairly common spring and fall migrant in the Western Upland and Central Plain, uncommon and local in the Northern Highland. Spring migrants arrive 10-20 April (earliest-4 April 1974, Burnett County), reaching peak abundance 1-5 May. Fall migration begins about 15 August in the Northern Highland and 25 August to 1 September elsewhere. Peak numbers occur 1-20 September. Departure from the Northern Highland occurs 20 September to 1 October; departure elsewhere is 10-25 October.

Nesting Season Distribution: Fairly common and well distributed in all regions. Breeding pairs occur with greatest frequency in the prairie wetland region of St. Croix, Polk, and Washington counties, and at Crex Meadows, Burnett County. Documented nest records exist for St. Croix, Polk, Burnett, and Washington counties. Evidence of nesting exists for the remaining counties. Jackson (1941) reported flushing one American bittern from a marsh at the headwaters of the St. Croix River in Douglas County on 8 August 1919.

Winter: Wayne Norling observed a single bird at Crex Meadows, Burnett County, on 9 January 1976.

Habitat: American bittern breeding habitat use varies with geographic province. Typical breeding habitat in Western Upland includes seasonally, semipermanently, and permanently flooded wetlands. Vegetation associated with these wetlands includes river bulrush, cattail, softstem bulrush, hardstem bulrush, and phragmites. Preferred habitat in the Central Plain is similar with a higher percentage of reed canary grass in seasonally flooded wetlands. Occasionally this species uses upland fields including Haylands, oat fields, Managed Grasslands, and retired cropland for nesting. In the northern regions of the Central Plain and throughout the Northern Highland, breeding habitat includes cattail-bulrush marshes. A high percentage of breeding pairs occur in sedge meadows in this region, as well as edges of Black Spruce-Tamarack Bog and northern Forest Bordered Lakes.


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