Abstract
The influence of varied nest box installation densities on the usage rate by Tree Sparrow Passer montanus and tit species Parus spp. was investigated at a golf course in Nagatake, central Japan. Increasing nest box densities negatively affected nesting by Tree Sparrows, but positively affected that by tit species. The effect of environmental temperature was also analyzed, and increased temperatures were shown to correlate with increased nesting by Tree Sparrows, but had no relationship to tit nesting. These results suggest that the population of Tree Sparrows may be restricted by food resources, rather than by a limited availability of nest sites. As a result, if the number of nest boxes are increased, Tree Sparrows may not increase nesting rates, and more nest boxes would be available for use by tit species. Increasing the installation density of nest boxes may be an effective method for enhancing the population of tit species. The mechanism causing the number of Tree Sparrow nests to decrease when nest box densities were increased is unknown, and requires further study.
