The use of space by white-crowned sparrows: Juvenile and adult ranging patterns and home range versus body size comparisons in an avian granivore community

Abstract

1. Ranging behavior in a nonmigratory population of white-crowned sparrows Zonotrichia leucophrys nuttalli residing in the coastal scrub habitat of central California was studied by trapping and recapture. Over 12,000 captures of more than 1,700 individuals were analyzed. In their first breeding season, young Z. l. nuttalli produced from early broods bred near their own hatching site, but those from later broods bred farther away (Fig. 3). 2. As adults, females had more restricted movements in summer than did males. In winter, females expanded their ranging movements more than males. We hypothesized that higher vagility of females in winter is related to their being socially subordinate to males in flocks. This causes them to wander among different flocks or to live a solitary existence. 3. Employing a bivariate statistical model we found the most satisfactory description of home range size to be given by a 50% equal frequency ellipse. By this method, the average Z. l. nuttali home range was estimated to be 6–7 ha (Fig. 6). 4. The home range of four other passerines in the same trap system has been estimated previously. We compared our results on Z. l. nuttalli with reported results on the four other passerines to examine the relationship between home range size and body size among granivores. The best-fit line has the equation: home range (ha)=0.044 W(g)1.31 (Fig. 7). The slope of this line is much steeper than that published for the relationship of mammalian home range and body size and is slightly steeper than indicated by previous work on birds. Our slope is also steeper than that of the relationship between standard metabolic rate and body size for passerines but is similar to a theoretically derived regression coefficient describing the power required for flight in relation to body size. We hypothesized that in birds the energetic demands of flight have influenced the evolution of home range size.