The 3 6 hover frequently during patrolling flight, and fiercely chase rival S3. Their patrolling flight was videotaped and analyzed. The average net-patrol flight speed (except hovering) was 161.6130.6 cm/s faster in the morning and the evening than during the day. Also, hovering frequency was more frequent and the duration of hovering bouts was longer in the morning and the evening than during the day, and was synchronized with patrolling flight speed. However, chasing flight was not related to patrolling or hovering and the duration of chasing bout was about 4-5 seconds with an average flight speed of 274.6±64.7cm/s. The body temperatures of patrolling flight and chasing flight were significantly different; the former, 39.811,4°C, the latter was 40.4il.0°C. The time budget of patrolling males based upon video pictures was calculated and the relative energy expenditure of patrolling 3 3 was estimated by standardizing the average net-patrolling flight speed as 1. Energy expenditure of the 3 3 was greater in the morning and the evening than during the day. It is assumed that energy expenditure was affected by ambient temperatures, with 3 3 changing the flight speed and duration of hovering. The 3 3 are inferior in their sex recognition and it is assumed that their frequent hovering with concurrent large energy expenditure is to enable 3 3 to distinguish 9 9.