Honey bee drone flyways and congregation areas: radar observations

We used an X-band radar unit to document honey bee (Apis mellifera) drone flyways and drone congregation areas (DCA's) in a nearly flat desert area. Within an approximate 5.0 × 2.0 km area adjacent to a commercial apiary, 18 km of flyways and at least 26 DCA's were located. The studies conducted during March and April in each of 4 years (1987-1990) confirmed that the location of flyways and DCA's were re-established day after day and year after year. Based on film records of radar images, our definition of a DCA is that site (≈ 100 m diam) where drones fly higher and are more numerous than in adjacent flyways. Flyways formed alongside the most prominent structural or physical features-e.g., tree lines formed in washes-but these flyways also branched, particularly when additional tree lines became visible on the near (≈ 200 to 250 m) horizon. Most DCA's occurred at these branch points; thus, the accumulation of drones at a DCA may be a result of rapid turning and altitude changes as the drones re-orient and select their next flight direction. The maximum height of drones in flyways was 21 m, whereas in DCA's they flew mainly from 30-50 m above ground. Flyways are more predominant than DCA's, and contain large numbers of drones. It is suggested that queens flying within or to the upwind side of flyways should attract sufficient drones to become easily mated.