Robbing during feeding: how not to turn your own apiary into a battlefield

You are feeding the colonies up for winter, everything goes smoothly, and then one afternoon a cloud of frenzied bees forms under one hive, a brawl rages at the entrance, and a layer of corpses grows on the landing board. This is robbing, and if you do not put it out in time, it can rob and kill in a single day the very colony you were carefully feeding. The worst part is that robbing is nearly always triggered by the beekeeper, and precisely when they mean the best for the bees, that is during autumn feeding.

September and the late-season dearth are the peak of the robbing season. In nature it is already empty, the flows are over, while in the hives there is store and syrup is flowing. For a strong colony a weaker neighbour or a spilled drop of syrup is an invitation to attack. Below I take robbing apart: where it comes from, how to recognise it, how to feed so as not to trigger it, and what to do once it has started.

Where robbing comes from

The mechanism is simple and brutal. When nectar is scarce in nature, bees do not stop looking for sugar, they start looking for it everywhere, including where they should not. The smell of syrup or exposed honey carries far and draws scouts from other colonies. If they hit a source no one is defending, they come back for reinforcements, and in a short time a swarm of raiders forms under the hive, breaks through the guard, forces its way inside and carries off the store, killing the defenders along the way.

The key thing is that robbing feeds on weakness and opportunity. A strong colony with a small, well-manned entrance will fend off an attack, because it has something to defend the gate with. A weak colony, with a wide-open entrance a handful of guards cannot watch, is defenceless. And the opportunity is most often created by you: by spilled syrup, by feeding that smells across the whole apiary, by keeping a hive open too long, or by a comb of honey left out on top.

And one more thing that often escapes notice: it is not only foreign bees that rob, but your own too. In a dearth a strong colony will just as gladly rob a weaker neighbour from the same apiary. Wasps and hornets join the raiders, homing in by smell on the same source. So robbing is not a problem of bad neighbours over the fence, but a matter of managing your own apiary.

How to recognise robbing

Robbing is easy to confuse at first with a cleansing flight or heavy foraging traffic, and the difference is crucial, because panic and needlessly shutting in a healthy colony do harm too. Here is how to tell it is really robbing.

Above all, fighting at the entrance and in front of the hive: bees locked in balls of two or three, tumbling on the board and on the ground, fighting to the death. That is the surest sign, because in normal flight bees do not fight.

On top of that a characteristic nervous, high-pitched tone of flight and chaotic, zigzag circling under the hive, unlike the calm, purposeful flight of foragers. Raiders do not fly straight to the entrance but nose along the walls, cracks and box joints, looking for a side way in. This is one of the best signals: a bee that has a right to be here goes in through the entrance, while a robber sniffs around the hive.

On the board and in front of the hive a layer of dead bees builds up, along with shreds of wax and cappings, because the robbers tear open the cells to get at the store. There are also hairless, dark, shiny bees, because they lose their hairs in the fight. And a bee leaving a robbed hive is heavy and drops down from the entrance, laden with stolen honey, unlike a light forager setting out for a flow.

A simple test in case of doubt: close the entrance almost to nothing for a moment. If after a few minutes disoriented bees swarm at the entrance looking for a hole to get in, those are robbers, because the residents would simply queue up calmly.

How to feed so as not to trigger robbing

The best robbing is the one you do not let happen, and with autumn feeding you have full control over that. A few rules that handle most of the problem.

Feed only inside the hive. A top feeder or a frame feeder the bees reach from inside the nest is safe, because the smell of the syrup does not get out and foreign bees have no way to find the source. Do not put feed by the entrance or anywhere the smell or the syrup itself are accessible from the entrance side, because that is an outright invitation to robbing. It is also good to give the feed towards evening, when flights are dying down, so the colony can take it quietly overnight before the daytime traffic starts.

Do not spill syrup and clean up every drop. It sounds trivial, and it is one of the most common causes. A few drops spilled by the hive are enough to draw scouts. If you spill something, wash it off or cover it with soil at once. Do not leave sticky buckets, cans or tools in sight.

Never feed openly, across the whole apiary. Setting out a bucket or trough of syrup somewhere in the apiary for the bees to help themselves is a robbing factory. You create a frenzy, and when the syrup runs out, the enraged bees fall on the nearest weak hive. Feed each colony separately, in its own hive.

Narrow the entrances, especially for weak colonies. During feeding and the dearth the entrance should be small, small enough for a handful of guards to watch. It is the simplest and cheapest insurance. Narrow weak colonies and nucs the most, because they die first.

Do not keep a hive open or tempt with smell. Do inspections during a dearth quickly and efficiently, do not leave out combs of honey on top, cover the boxes you set aside. Every minute of an open, honey-smelling hive during a dearth is a signal to the whole neighbourhood.

Keep strong, even colonies. The best defence against robbing is a strong colony that guards its own entrance. In autumn it is better to unite weak colonies into stronger ones than to hope they somehow survive, because a weak colony is not only a poorer wintering but also a magnet for robbing.

What to do once robbing is under way

If you see robbing under way despite everything, act at once, because every hour of delay means store carried off and bees dying. The order is roughly this.

First, drastically narrow the entrance. This is the fastest and most effective move. Reduce the entrance to a gap for one or two bees, stuffing grass, foam, a piece of wood, anything, into it. A smaller gate is a shorter line of defence the residents will reclaim and the raiders will lose their easy way in.

Throw a wet sheet over the hive. An old, tried trick. You drape a damp sheet over the robbed hive so it covers the walls and the entrance but does not lie tight to the ground. The home bees know their hive and come out from under the sheet at the bottom, while the disoriented robbers lose the trail, because the sheet masks the smell and blocks the entrance they were battering at. The wetting also cools and calms the frenzy. You keep it on until the guard regains control.

Consider a robbing screen. In Poland few people use it, but in the English-speaking world it is a popular gadget: a mesh cover over the entrance that redirects the way in. The home bees learn the roundabout route inside, while the robbers, flying straight at the smell, hit the mesh and do not get in. In practice, at home, the same is usually handled by heavily narrowing the entrance and a wet sheet, so treat the screen as an option, not a necessity.

Remove everything that lures. Take away any feed accessible from the entrance side, clean up spilled syrup, hide combs and any honey in sight. As long as the source smells, the robbing will not let up.

As a last resort, close or move the hive. In violent robbing you can shut the colony in for a day or two, seeing to ventilation and water, so it calms down and reclaims the gate. And if the robbing is extreme, the most effective thing is to move the robbed colony a few kilometres away, out of the raiders' range, until the situation dies down.

And one important rule during robbing: do not open the hive to check the queen or the store, because you will only pour oil on the fire, releasing more smell and drawing further raiders. Leave the diagnostics for a calmer time.

Breed matters too

Not all bees rob equally readily. A greater tendency to rob is ascribed to the Italian bee and its hybrids, which goes with its temperament and its drive to gather at any cost, whereas the Carniolan or Central European bee is regarded as somewhat calmer in this respect. This is a broad generalisation, though, because within every breed there are gentle and rowdy colonies, and temperament can shift depending on the flow and the time of the season.

And a caveat at once, so as not to draw hasty conclusions: a more vigorous, energetic colony, the same one that robs more readily, is often better at many other things too, whether coping with varroa or in production. A tendency to rob is not a fault to be bred out, but a trait of temperament that you simply have to know and must not provoke through mistakes in management. In other words, breed explains why some colonies rob more than others, but the answer is still not to change the bee, but sensible feeding and narrowed entrances.

And what if I do not feed? Robbing as a consequence of hunger

There is another side to this, easy to forget when you focus on defence. Since robbing is driven by hunger and lack of a flow, a colony you fail to provision will set out robbing itself. A hungry, strong colony will not sit on its hands and wait to die, it will send out scouts and strike at weaker hives, at yours or the neighbour's. In other words, neglecting feeding not only exposes your colony to hunger but also turns it into an aggressor that cranks up robbing across the whole area.

And here we come to the most dangerous consequence, far more serious than the stolen honey itself: robbing is one of the main routes for spreading disease. Raiders forcing their way into a foreign, often weak and sick hive carry off not only the store but the pathogens, which they bring straight into their own nest. And weak colonies are weak for a reason, because behind their poor condition there is very often disease. What can you drag home this way?

Above all American foulbrood. The peak of this disease falls in late summer and early autumn, exactly in the robbing season, and that is no accident. Robbing a sick colony is a classic route for spreading the spores, which the raiders take with the infected honey and bring to a healthy nest. Worse still, it is the strong colonies that fall ill first, because in a dearth it is they that rob the weaker, sick ones, infecting themselves.

Then varroa, because along with robbed bees and through contact in a foreign hive the mites move between colonies, and dying, plundered colonies become literally a varroa bomb for the whole neighbourhood. On top of that nosema, because the spores travel with the robbed store and the fouled nest, and viruses, including those spread by varroa. Robbing is thus a motorway on which all these diseases jump from hive to hive.

The conclusion is simple and rounds off the whole topic: feed the colonies in time and properly, not only so they do not die of hunger, but also so they do not set out robbing and drag foulbrood, varroa or nosema into your apiary. Good store management is not only a matter of surviving winter, but also disease prevention on the scale of the whole apiary.

Curiosities and controversies

Robbing is nearly always triggered by the beekeeper. It is an uncomfortable truth, but most robbing does not arise from nature, it arises from a management error: spilled syrup, daytime feeding, a wide-open entrance on a weak colony, a hive kept open too long. The good news is that since we trigger it, we can eliminate it almost to zero.

A wet sheet works, though it sounds like superstition. Draping a damp sheet over the hive looks like a folk trick, and it is recommended even by serious beekeeping sources. The secret is double: the sheet masks the smell and blocks the entrance the robbers are looking for, while the home bees find their way out from under it anyway, because they know their hive. The wetting also calms the frenzy and cools the colony.

Open feeding is robbing on demand. Some beekeepers set out syrup in buckets for the whole apiary, counting on convenience. In practice it is steering the robbing: it creates a frenzy, and when the syrup runs out, the enraged bees fall on the weakest hive around. It is a method that can do more harm than the few minutes saved are worth.

There is a bee called the black robber. One form of chronic paralysis gives hairless, dark, shiny bees, which in that state often wander and rob foreign hives, hence the folk name black robber. They are easily confused with ordinary robbers, which also lose their hairs in the fight, but here the glossy black comes from disease. It is a good reminder that robbing and disease are entwined in many ways.

A robber gives itself away by how it flies. Before the brawl even starts, you know a robber by the fact that it does not fly straight to the entrance but sniffs along the walls and cracks, looking for a side way in. A home bee always aims for the entrance. Whoever learns to read this detail will catch robbing in the bud, before it does damage.

Most common mistakes

Spilled, uncleaned syrup. A few drops by the hive are enough to draw scouts. Wash or cover every spill at once.

A wide entrance on a weak colony. A weak colony with a wide-open entrance has nothing to defend the gate with. During a dearth and feeding, narrow the entrances, most of all on weak ones.

Delay after spotting robbing. Robbing grows like an avalanche, so every hour of delay means store and bees lost. React at once, with narrowing and a sheet.

Opening a robbed hive. Looking inside during robbing releases smell and draws further raiders. Leave the diagnostics for a calmer moment.

Open feeding, across the apiary. A bucket of syrup in the middle of the apiary is a robbing factory. Feed each colony separately, in its hive.

Sources and further reading

• Downs S. G., Ratnieks F. L. W. (2000). Adaptive shifts in honey bee guarding behavior support predictions of the acceptance threshold model. Behavioral Ecology 11: 326-333. On how, in a dearth, guard bees tighten defence of the entrance, that is the natural mechanism guarding against robbing.

• Couvillon M. J. et al. (2008). En garde: rapid shifts in honeybee guarding behaviour are triggered by onslaught of conspecific intruders. Animal Behaviour 76: 1653-1658. On the sharp rise in guard numbers under the onslaught of robbers.

• Grume G. J., Biedenbender S. P., Rittschof C. C. (2021). Honey robbing causes coordinated changes in foraging and nest defence in the honey bee, Apis mellifera. Animal Behaviour 173: 53-65. On robbing as a coordinated foraging strategy under scarcity.

• Polish beekeeping literature on bacterial brood diseases (e.g. Glinski, Pasieka24) on robbing as a route for spreading American foulbrood, and the breeds-and-lines guidance of agricultural advisory centres on the robbing tendency of the Italian bee and its hybrids.