Functional Analysis of Space‐Related Behavior in the Seaside Sparrow

Abstract

This paper compares Seaside Sparrow (Ammospiza miritima) populations nesting in two dispersion patterns: territories and grounded territories. Territories, found in altered (ditched) salt marshes, were large, all—purpose activity spaces. Grouped territories, found in unaltered salt marshes, were small activity spaces from which birds made distant foraging flights. Among the factors influencing the grouped territory spatial pattern the most important were nest site, availability and lack of predation. A scarcity of nest sites in the unaltered habitat appeared to require the birds to nest close together, while such aggregation was made possible by scarcity of ground predators. The territorial pattern was thought to be influenced by low population density, low food availability, and sufficiency of nest sites. The amount of time that birds spent foraging, singing, and resting did not differ between spatial patterns, nor did the diurnal pattern of these activities. Birds on grouped territories spent more time in aggression than did birds on territories. The breeding success of birds found in the two dispersion patterns did not differ. The rate of delivery of food to the nest was also the same, although birds on territories flew twice as far to gather food for their nests. The results suggest that both spatial patterns are equally successful for the given conditions. Because of its variability it is doubtful that the space—related behavior of the Seaside Sparrow acts to limit population size.