 However, they normally only spend 30 minutes per day in flight.This is reduced to an average of 490 beats per minute while resting at night, and declines to an average of 375 beats per minute while resting during the day.Their daytime heart rate is periodically (two to three times per hour for 5 to 7 minutes per episode) lowered further to 200–250 beats per minute as part of an apparent strategy to reduce energy expenditure.