Ordinarily, bees in separate colonies get along with each other well because they have innate behavioral skills to recognize their own colony and carefully mind their own business. Sometimes, bees are deliberately kept in hives that are literally touching each other. Those bees go in and out of their own colonies with little stress, though their entrances are only inches apart. Even in widely separated colonies, bees — especially drones and returning foragers — may drift from hive to hive and arouse no serious antagonism. It's a very different story when there is robbing going on.
What is hive robbing?
A type of foraging behavior, “hive robbing” is the term for when bees steal honey from another colony. Because honey bees collect and store much more honey than needed for immediate use, they often have a surplus of resources to defend. Honey is literally the difference between life and death, and robbing can be a problem — whether your bees are the target or the offenders.
Why do bees rob other hives?
While beekeepers call this type of foraging "robbing," another way to think about it is a reallocation of resources. Stronger hives, with a better chance of survival due to higher population numbers, will seize honey from smaller, weaker hives. Their vulnerability may be due to natural causes — being young colonies or nucs — or due to troubles such as diseases, pests, or low population during a requeening cycle.
Robbing can also be inadvertently started while there are limited or no other foraging opportunities. This is particularly true in a seasonal dearth, or at the end of the year. In those instances, there can be so much intense foraging pressure that even full-sized hives may wind up being robbed.
Impact of robbing bees
Even when a hive can successfully repel the invaders, many bees will be needlessly lost in the struggle, the colony's — and the apiary's — overall stress level will increase, and diseases and parasites will be spread around. That potential for contagion makes robbing dangerous to all colonies. Even if your colonies are the ones doing the robbing, they will likely bring home “souvenirs," in addition to the honey they looted. Robbing is one of the principal ways Varroa destructor mites and various bee diseases are spread.
Bees going in and out of a robber screen
How to tell if bees are robbing a hive
Robbing most commonly looks like an alarming flurry of activity in front of and around the hive. To identify robbing, look closely at the entrance area: If you see pairs or triads of bees grappling with each other, rolling around, and trying to sting each other, then it is most likely robbing. Morgue bees carrying out the hives' dead may look like they are fighting, but that may be from the awkwardness of carrying corpses. If you knock down a morgue bee carrying a dead bee, she will simply drop it and fly calmly back to the hive. Fighting bees, on the other hand, will continue to engage with each other and can be hard to pull apart.
Another way to tell is to look at your screened bottom board to examine the debris that has fallen through. Robbing leaves behind the telltale evidence of a raid in the form of lots of large, ragged-edge crumbs of cappings torn away during the honey theft. Normal opening of stored honey generates only tiny holes, quickly repaired after the needed honey is drawn off. Robbing bees don't have time for that nicety; they rush in and grab what they can before they are discovered.
Robbing versus orientation flights
Robbing can look similar to a large orientation flight, but you can spot the differences if you look closely. Robbing is almost always accompanied by visible fighting among bees on the landing board — except in its last stages when the victim is nearly overwhelmed.
The other way to identify an orientation flight is the time of day and the length of time they continue. Orientation flights are generally afternoon affairs, when the day is warm, and they usually last only 20 to 30 minutes at a time. Robbing, however, goes on until dark and will begin again at first light.
A more subtle way to tell them apart is the demeanor of the bees. Orientation flights have a buoyant, almost playful quality to them. (“Whee, I can fly — so that's what wings are for!”) Robbing, especially a full-blown attack, has a grim, menacing feel as the would-be robbers dart around looking for the right opportunity to slip into the hive.
Large jagged crumbs of wax due to robbing
How to stop robbing bees
The best advice is to always be aware of the possibility of robbing and prevent it before it starts. Keep your colonies strong, and if necessary, consider somewhat reduced entrances, even when there is flow on. The full-width entrance of Langstroth design hives is usually unnecessary. Try leaving the reducer in, and just slanting it outward. Feral colonies often have surprisingly convoluted and small entrances, so your bees will adapt. Explore these quick tips for preventing — or stopping — hive robbing:
- If you suspect robbing, immediately add an entrance reducer and a robbing screen. This will help the guard bees maintain, or regain, control of the entrance.
- Make sure your beekeeping manipulations do not needlessly promote robbing. Plan ahead for whatever you might need and have it on hand, so you can minimize the time the hive is open.
- Keep boxes covered up during inspections by stacking and covering them (lightweight political signs make great temporary covers) and don't leave honey frames exposed during the harvest.
- Clean up any spilled syrup or comb broken during inspections.
- Don't common-feed near hives.
- A surprisingly useful tactic is to cover the victim colony with a wet sheet as soon as you notice robbing behaviors, and keep it wet until you can get the entrances under control. Similarly, a lawn sprinkler kept running continuously over the hive area may create the illusion of a rainstorm, sending robbers back to their own colonies.
- At dusk, when all the home bees are back inside, it may be wise to move the victim colony to another location, especially if it is a smaller one, like a newly made-up nuc.
Entrance reducer install on a slant
Using entrance reducers and robber screens
You can't stop your bees from going out robbing, but you can install robber screens on your colonies to prevent them from becoming targets. The best time to install robbing screens is before they are acutely needed. That way the bees can become accustomed to them. The screens' entrances are usually adjustable, so you can leave the entrance wide open when it’s not needed, then quickly narrow it down to a single bees’ width if robbing occurs.
An entrance reducer closes up part of the entrance, while a robber screen covers the entire entrance area, creating new entry points. They can be used together, or separately. Routine use of robber screens won’t interfere with colony operations — the bees will quickly adapt. If you have upper entrances, you can use a nuc robber screen over that entrance.
Robbing screens work by reducing the amount of space the guard bees need to patrol, thereby maximizing their effectiveness, and also by creating a displacement between the entry point of the screen and the actual entry point into the colony. Bees in a hive will lay down scent trails over and underneath the screens so that foragers will be able to find the most efficient way through the screen. Interestingly, if your yard is fully equipped with identical robbing screens, bees from one colony don't seem to be able to figure out how to negotiate the pathway into another colony.
While robbing is a natural bee behavior, it carries with it a high risk of catastrophe for all parties involved. It shouldn't be ignored because it can lead to the complete loss of a colony. You can easily reduce the risk by being prepared and taking care while you work your bees. For more beekeeping tips and advice, explore our Beekeeper Guide.
