The decrease of flying insects may be one causative factor in the observed decrease of summer resident birds in Japan, however, the author is unaware of any studies on insect abundance that addresses this potential relationship. Therefore, a pilot study to evaluate a convenient method to monitor flying insects was conducted in west-central Tokyo. The numbers of flying insects on the lighted panels of soft drink vending machines, located in several typical outdoor environments, were counted at night from April to August in 2005-2006. During April to June, the abundance of insects was greater along the river than in other areas, while the difference was smaller during July to August in both 2005 and 2006. The patterns of seasonal changes in the abundance of insects were similar between 2005 and 2006. The arrival periods of Barn Swallows Hirundo rustica at nest sites in two locales appears to correspond with the observed pattern of insect abundance. The majority of swallows nesting along river sites arrived earlier than those at other locations, possibly to correspond with the early peak in insect abundance that was recorded at the river sites. These results suggest that counts of insect abundance at lighted vending machines can be an adequate method of monitoring the relative abundance of flying insects as a food resource for birds. Further investigation and refinement would enhance the value of this convenient technique.