BIRDS OF THE ST. CROIX RIVER VALLEY 



29 



nesting was noted at Crex Meadows in 1968. This colony was in a heron 

 rookery on Phantom Lake. Because of degredation of nesting trees, the 

 Phantom Lake colony declined, and birds moved to the Grettum Flowage at 

 Fish Lake WildUfe Area. In 1973, 23 nests were observed in the Grettum 

 Flowage colony. 



Habitat: Both Phantom Lake and Grettum Flowage are large impound- 

 ments characterized by deep water and dead trees. This temporary habitat 

 type was created when tree growth in these basins was inundated by rising 

 impounded waters. Construction of nest platforms in the Phantom Lake 

 colony has attracted several breeding pairs. This management practice may 

 prove essential in the maintenance of these two colonies. 



FAMILY ARDEIDAE: Herons and Bitterns 

 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 (earUest— 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 Septem- 

 ber and most depart by 10 November (latest— 20 November 1964 and 9 De- 

 cember 1971, Burnett County). 



Nesting Season Distribution: Fairly common and local nesting species 

 throughout the Valley. Evidence of nesting has been documented in all coun- 

 ties except Pierce. The two largest rookeries in the region are at Crex 

 Meadows Wildhfe 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 (WiUiams 1957). The Crex Meadows rookery located on 

 Phantom Lake was first used in 1952 (WiUiams 1957). Further records 

 related to the breeding population of this rookery follow: 



1958— 157 active nests 

 1960— 108 active nests 

 1962—109 active nests 



1968—160 active nests. Rainstorm (8.5 cm) on 30 June left 65 nests in the 

 rookery. About 150 herons were found dead near the rookery. 



1973— 169 active nests, Phantom Lake; 13 active nests, North Fork 

 Flowage 



1974— 143 active nests in four rookeries 



1975— 75 active nests in the Phantom Lake rookery 



1976— 31 active nests 



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 



