30 



NORTH AMERICAN FAUNA 73 



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 Uving green ash and American elm associated with the Lowland De- 

 ciduous Forest community. One rookery in the Northern Highland is in Uv- 

 ing 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 Po]k counties. Fairly com- 

 mon in the Central Plain, and uncommon and local in the Northern High- 

 land. 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 Sep- 

 tember 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 sea- 

 sonally, 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. 



