Flight Activity Monitors

A flight activity monitor (bee counter) is a device that tracks a colony's foraging activity without opening the hive by counting the bees entering and leaving the entrance with infrared gates, cameras or similar sensors. Sudden drops suggest poisoning or forager loss; unexpected rises suggest robbing or swarming. Because the data depend heavily on the weather, correct interpretation requires comparison with other hives in the same apiary and with weather conditions.

What is a flight activity monitor?

The hive entrance is the colony's connection with the outside world. The number of foragers, their flight times and the bees that do not come back say a great deal about the colony's strength and the risks around it. A flight activity monitor records this traffic continuously and in numbers.

Beekeepers also call these devices "bee counters", "entrance counters" or "traffic sensors". Long used in research, these systems have in recent years also been offered to beekeepers as part of sensor-equipped hive kits.

How do flight activity monitors work?

There are several ways of counting bees; each has different strengths and weaknesses.

With every method, the main difficulty is that bees lingering, fanning or walking back and forth at the entrance get counted more than once. So the number these devices give is not absolute but a relative indicator: it is compared with itself from day to day.

What does flight data tell you?

The normal daily pattern

• Dependence on weather: Flight drops sharply below about 10–12 °C; rain, strong wind and cloud cover reduce traffic.
• Morning start and midday peak: When there is forage, traffic rises in the morning and peaks in the warm hours of the day.
• Afternoon orientation flights: Young bees make orientation flights in front of the hive; this "crowd" is not a sign of forage or of swarming.

Signs to watch for

• A widening gap between bees leaving and returning: If a noticeable share of departing bees does not return, foragers are being lost. The cause may be pesticide poisoning, hornets hunting in front of the hive (e.g. Vespa orientalis) or a sudden change in the weather.
• A sudden, sharp drop in good weather: Poisoning or a serious colony problem; check for dead bees in front of the hive.
• Heavy traffic with no forage: Suspected robbing, especially if there is fighting at the entrance.
• A very large outflow over a short time: A swarm leaving; confirmed by a simultaneous weight drop on the scale.
• A slow decline over days: The colony may be weakening or the forage running out.

Which decisions can flight activity data help with?

1. Suspected poisoning: During agricultural spraying periods, a drop in the forager return rate is an early warning; it gives you time to contact whoever is spraying and to take samples.
2. Hornet pressure: Returns dropping at certain times of day suggest hunting in front of the hive; this can be used to time traps and entrance measures.
3. Tracking forage: Together with scale data, if traffic is high but weight is not rising, the bees may be flying for water, pollen or a distant, weak source.
4. Comparing hives: A hive that consistently shows lower traffic than the others in the same apiary is moved up the inspection list.

Counting flights by hand: monitoring without a device

Traffic can be monitored without an expensive monitor. On a sunny, windless day, always at the same time, count the bees returning to the entrance for one minute. If all the hives in the apiary are counted on the same day, a colony that is lagging behind stands out at once.

• Have the same person do the count, at the same time and in similar weather.
• If you count pollen-carrying bees separately, you also get an idea about brood rearing: if the proportion of foragers bringing pollen is high, the colony is usually raising brood.
• Write the results on the hive record card; a series is meaningful, not a single count.

What should you look for when choosing a bee counter?

• Entrance narrowing: Tunnel counters narrow the entrance. In hot weather and strong flows traffic can jam and ventilation can suffer; the number and width of the tunnels should suit the strength of the colony.
• Direction detection: A system that can tell incoming from outgoing bees gives far more information than one that only measures "movement".
• Ease of cleaning: Tunnels and lenses get dirty with propolis, pollen and dust; they should be easy to remove and clean.
• Power: Camera systems need more power; the solar panel and battery capacity should suit the apiary.
• Data: Recording together with air temperature, exportable data and the ability to set alerts.
• Fit with your hive type: Mounting compatible with the entrance dimensions and the winter entrance reducer.

Installation and maintenance

1. Fit the counter to a medium-strength, representative colony; ideally, compare it with hives without counters in the same apiary.
2. After fitting, give the bees a few days to get used to it; data from the first days are not typical.
3. In hot periods, watch for signs of bearding and entrance blockage; open extra ventilation if necessary.
4. Clean tunnels and lenses regularly; a single dead bee or piece of wax is enough to spoil the count.
5. In winter, especially with entrances narrowed against mice and cold, it is often better to remove and store the counter.

Limitations and common interpretation mistakes

• Taking the number to be an absolute count of bees; the devices give relative trends.
• Mistaking the drop on bad-weather days for a problem; the data should be read alongside weather data.
• Mistaking orientation flights for swarming or robbing.
• Thinking the monitor will give information about disease, the queen or the brood; those require an inspection.
• Not noticing that a counter narrowing the entrance is stressing the colony in hot weather.