BIRDS OF THE ST. CROIX RIVER VALLEY 



153 



Yellow-headed Blackbird (Xanthocephalus xanthocephalus) 

 Status: Regular migrant and nesting species. 



Migration: Fairly common (locally common) migrant in the Western Upland, 

 uncommon and local in the Central Plain, and rare in the Northern Highland. 

 Spring migrants arrive in the Western Upland about 15 April, reaching the 

 Northern Highland by 1 May. Peak spring abundance occurs 1-15 May and 

 nonbreeding birds depart by 20 May. FaU migration begins with dispersal 

 from breeding marshes and the formation of loose flocks in late July. Peak 

 fall abundance occurs 15 August to 1 September and departure by 30 Sep- 

 tember (latest— 9 October 1966, Washington County). 



Nesting Season Distribution: Common to locally abundant breeding bird in 

 central St. Croix, Washington, and southern Polk counties. I conducted a 

 census of breeding yellow-headed blackbirds in 1975 and found over 1,000 

 pairs in central St. Croix County; a 1977 census yielded fewer than 500 pairs. 

 The difference was attributed to persistent drought conditions. Documented 

 breeding records exist for St. Croix, Washington, Polk, and Burnett coun- 

 ties. Breeding Bird Survey data (Table 7) suggest that the largest breeding 

 populations occur in the Western Upland. An isolated breeding population 

 exists at Crex Meadows WildUfe Area, Burnett County. EUarson (1950) re- 

 ported two additional colonies in Burnett County in 1948 and 1949 which 

 were still occupied in 1977. Green and Janssen (1975) stated that this species 

 is absent from "much of Pine County." 



Habitat: Characteristic nesting species of deep semipermanently and perma- 

 nently flooded wetlands. Predominant vegetation associated with yellow- 

 headed blackbird nesting habitat includes cattail, river bulrush, hardstem 

 bulrush, and phragmites. 



Red-winged Blackbird {Agelaius phoeniceus) 



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



Migration: Abundant migrant throughout the Valley. Spring migrants 

 arrive in late February in the Western Upland, reaching the Northern High- 

 land by 15 March. Peak spring migration occurs 15 March to 10 April. Fall 

 migration begins in mid-July with dispersal from nesting areas and the 

 formation of loose flocks. Numbers gradually build through August reach- 

 ing peak abundance 10-25 September. During this period, roost flocks 

 ranging from 25,000 to 50,000 individuals can be observed. Most fall mi- 

 grants have departed by 1 November; however, stragglers remain into early 

 December. 



Nesting Season Distribution: Abundant nesting species in the Western 

 Upland and Central Plain, common in the Northern Highland. Breeding Bird 

 Survey data (Table 7) suggest that a very large breeding population exists in 

 the open agricultural areas of the Western Upland and Central Plain. This 

 breeding population diminishes in abundance in the more forested Northern 

 Highland. 



