Drone congregation area

Drone congregation area (DCA) is a place where drones fly most of the time after leaving the nest. The DCA is 30-200 m in diameter and 15-40 m above ground [1][2]. Drones fly back and forth in this area producing audible sound similar to a swarm of bees. Drones can choose among many DCA near the apiary. During its life a drone can visit few different DCA. Sometimes more than one DCA is visited by the same drone during one day [3].

The same place can be chosen by honey bees as DCA year after year [4][5], however, it is not known what makes the places attractive to drones. It was suggested that choice of the places is related to perception of Earth's magnetic field [6][7] or visual features on the ground [8](observations of Buchmann reported in [9]). Usually there is an open space around DCA without trees or hils [10][1] see also [11]. Sometimes it is located over water or forest [12]. Formation of DCA can be affected by pheromones produced by drones [13]. Artificial DCA can be induced with large amounts of queen substance [14]. In order to confirm presence of DCA, caged queen fixed to a balloon is placed in mid-air [15]. Presence of DCA is indicated by drones congregating around the caged queen. Instead of the queen its pheromones can be used [16][17]. DCA can be also observed using radar [9].

In order to reach DCA drones travel up to 7 km and cross mountain ridges 800-1000 m high [5][18]. Mean flight distance of drones is 900 m [19]. The drones prefer DCA located close to the nest [20][21][22].

Number of drones present at DCA depends on weather and time of day. It can range from few hundred to few thousand [23]. In region with high density of honey bee colonies DCA was visited during one hour by 11750±2145 (mean±SD) drones (maximum 15290) [24]. Drones at DCA are not related and represent about 240 colonies [25] see also [26][27]. The same DCA can be visited by different subspecies [5] but timing of the visits can be different [12].

The concentration of drones is highest in the centre of DCA [28]. The diameter of DCA at higher distance from the ground is smaller and its centre is not always in the same place at different heights [28][29]. Drones fly to the DCA along tree rows and other features of landscape at maximum hight above ground 21 m [30]. Neighbouring DCA are often connected by flyways.

Queen is attractive to drones only within DCA. If queen is few meters outside the DCA (both in horizontal and vertical direction) drones stop pursuing her [1]. Distance above the ground where queen is attractive to drones differed between days and it is probably affected by weather [15]. It was suggested that drones visiting DCA release a pheromone which is attractive to queens [31].

Drones collected at DCA can be used to monitor the surrounding population. This can be useful in honey bee conservation areas [32] and for monitoring population density [33].

Review: [34]
Other references: [35][36][37][38][39][40][41][42][43]

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