Breeding Colonies and Foraging Habitats of Herons in Sedgwick County, Kansas

Abstract

Populations of wading birds in Sedgwick County, Kansas, were studied in 1991 to determine the size and species composition of active colonies, and to document the locations of major foraging areas. Two colonies were active that year: a rural one of 60-70 pairs of Great Blue Herons (Ardea herodius), and a larger colony in Wichita, which contained 530 nests of five species. Local breeding populations of wading birds are declining. Apparent high levels of mortality were evident in the mixed-species colony, with more than 160 eggs and 60 dead chicks found on the ground and in nests. Egg predation by American Crows (Corvus brachyrhynchos) also was documented. Interspecific differences were noted in the compass directions of foraging flights taken by birds from the mixed-species colony, and in the types of habitats used. Wading birds were observed at more than 100 foraging sites. The adverse effects of human activity have had an impact on the world's waterbird populations (King, 1981). These activities include: a significant loss of estuaries and freshwater wetlands, increasing competition for water between agricultural interests and wildlife populations, an increase in recreational activities and their negative effects on aquatic ecosystems, and the contamination of waterways and their food resources. In many ways, Sedgwick County, in south-central Kansas, exemplifies the problems of such human-wildlife interactions. This county has a large and growing human population (400,000), and an abundance of both agriculture--often associated with high pesticide levels-and industry--a major source of the heavy metals and other toxins which find their way into waterways. All these are problematic to waterbird survival. Sedgwick County also contains one of the largest populations of longlegged wading birds in Kansas, with eight species known to breed here. Some, such as the Great Blue Heron (Ardea herodias), nest virtually throughout the state; others, like the Great Egret (Casmerodius albus), breed in only one