Effective line intervals for controlling invasion of Eurasian Tree Sparrow, Passer montanus

Abstract

Bird nets are only reliable method to prevent crop damage from birds; however, it is difficult to set them on large fields. One of alternative methods is using lines. I tested whether lines are effective to prevent the invasion of Eurasian Tree Sparrow Passer montanus. I set a feeding tray inside a 2m wide × 1m high × 1m deep flame, where birds can enter upper side only. I recorded the entering frequency and the staying time with no-lines, 50, 40, 30, 20, 10, 5 and 2.5 cm intervals of lines over the flame top. There were no apparent differences between the frequencies of no-lines and 50 cm intervals. As the intervals got narrower, the entering frequency decreased. The average staying time was almost same （63-84 seconds）from no-lines to 10 cm intervals, but it was increased more than 250 seconds on 5 cm and 2.5 cm intervals. The entering frequency was 1/3 at 30 cm interval and 1/10 at 20 cm, compared to those of no-lines and 50 cm intervals, while the staying time was not increased at these intervals. Thus, intervals of 20 cm and 30 cm were effective as a countermeasure to Eurasian tree Sparrow. Although this is under the controlled condition, it will be applicable to suitable condition in the fields.