Relationship of fire history to territory size, breeding density, and habitat of Baird's sparrow in North Dakota

Prescribed fire often is used to manage prairies, but its effects on many grassland birds are not well documented. In 1993 I compared breeding density, territory size, and habitat of Baird's Sparrows (Ammodramus bairdii) among three different fire regimes in mixed-grass prairie in North Dakota: areas not burned in more than 80 years, areas burned twice since the late 1970s, and areas burned four times since the late 1970s. Baird's Sparrows were absent on unburned areas. They occurred at moderate densities ((X) over bar = 6.9 males/100 hectares) on two-burn areas; these areas were characterized by relatively high vegetation ((X) over bar = 18.5 centimeters), relatively deep litter ((X) over bar = 2.8 centimeters), and an absence of bare soil. Higher Baird's Sparrow densities ((X) over bar = 20 males/100 hectares) were found on four-burn areas where litter was low ((X) over bar = 0.08 centimeters), vegetation relatively short ((X) over bar = 13.8 centimeters), and the percentage of canopy coverage by bare soil relatively large ((X) over bar = 11.4 percent). Mean territory size was significantly smaller in four-burn areas ((X) over bar = 1.2 hectares) than in two-burn areas ((X) over bar = 1.5 hectares). Prescribed burning favorably changed habitat structure for Baird's Sparrow, as indicated by a clear tie between occurrence of burning and that of the species; observed changes in density and territory size with frequent burning further suggested a positive link between fire and Baird's Sparrows in northwestern North Dakota.