An index for assessing the foraging activities of honeybees with a Doppler sensor

Most pollination of commercial blueberries is carried out by honeybees from hundreds of hives. An activity sensor for monitoring the health and productivity of beehives is presented. Honeybees flying near the entrance of a beehive were observed with a low-powered 5.8 GHz Doppler radar. Spectral moments, entropy, diversity, and root-mean-square (rms) power were evaluated to identify foraging bees and to quantify the level of foraging activity. Theoretical and experimental results are presented to demonstrate that entropy, diversity, and rms power are correlated and are equally valid indicators of bee activity. In particular, the rms power of the Doppler signal can be measured without a coherent receiver and without signal processing. This type of measurement lends itself to a second, considerably less expensive, implementation of a bee activity sensor.