Interterritorial Habitat Variation in Grasshopper and Savannah Sparrows

Individual variation in features of habitat structure among territories of breeding grasshopper sparrows and savannah sparrows in a southern Wisconsin grassland was examined. Grasshopper sparrow territories established late in the breeding season were larger than those occupied earlier. In savannah sparrows, time of establishment had no significant effect upon territory size, but variation in the amount of grass cover was highly correlated with size differences. There was considerable inter—territorial variation in habitat features in both species, but patterns relating to territory size, position in the breeding population, and time of territory establishment were well—defined in savannah sparrows, whereas grasshopper sparrow territories generally showed little systematic pattern of variation. Although these species occupied similar habitat situations after breeding populations stabilized in mid—June, they initially established territories in quite different portions of the habitat spectrum.