Category Archives: Science

Too many honey bees (in town)?

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Synopsis : Honey bees compete with native bees. How many hives are too many, resulting in damage to native bee populations? Probably fewer than you think.

Introduction

Several years ago I visited Montréal to speak at an international symposium. It was a big conference with a very busy programme but I still managed to sneak away and see the city. We had a week or so of stunning Indian summer weather so I walked almost everywhere; along the banks of the St Lawrence and Prairies Rivers, through the Botanic Gardens and the Mount Royal 1 Park.

Montréal Olympic stadium from the Botanic Gardens

If you’ve not been I can recommend it.

However, I didn’t see a single honey bee.

I wasn’t specifically looking for honey bees, but beekeepers tend to notice these things.

In retrospect that wasn’t too surprising. At that time there were just a couple of hundred hives within the city, which covers an area of 430 km2 .

I did see monarch butterflies (Danaus plexippus) in the gardens, stocking up on nectar before starting their migration back to Central Mexico.

Monarch butterfly, Montréal Botanic Gardens

This was early October. Had there been lots of honey bees in Montréal I’d have expected to see them on the same asters, competing for the nectar with the butterflies, piling in the stores before the coming winter.

And competition isn’t always a good thing.

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Coffee, constancy and fidelity

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Synopsis : Why do bees collect pollen of only one type when foraging? Why do they forage repeatedly in the same area? What has coffee got to do with this?

Introduction

Foraging is what my bees should be doing now. The summer nectar flow should be strong – lime, blackberry, rosebay willow herb (RBWH, fireweed) then heather – it’s bonanza time.

But note the qualifier ’should’.

So far, it’s not looking promising.

The lime was hopeless, the blackberry flowered well but doesn’t appear to have yielded much, the fireweed is nearly over (early) and the heather … well, let’s not prejudge anything, but I’m not hopeful.

Going, going, gone … rosebay willow herb, mid-July 2023

Not only do those four plants/trees yield nectar, but they also produce pollen and you can often tell what the bees are foraging on by the colour of the packed corbiculae on the hind legs of returning workers.

Despite their overlapping flowering periods the pollen baskets are almost always a single colour. For example, you don’t get deep purple pollen baskets from RBWH speckled with much paler borage pollen, despite the fact you can find both flowering – in a field and its margins – simultaneously.

This is because honey bees tend to forage on one plant species 1 on any foraging trip. This feature of the foraging habit of honey bees is termed constancy.

If you marked a foraging worker on a patch of RBWH, watched it fly off to the hive and waited a bit you might well see the marked bee return to the same patch of RBWH and start collecting pollen or nectar again.

This is not constancy but is instead termed fidelity.

Both fidelity and constancy have consequences for plant pollination. It’s therefore unsurprising to discover that some plants have evolved to influence these foraging habits of bees … which is where the coffee comes in.

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Why so few feral colonies?

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Synopsis : With so many swarms lost by beekeepers, why are there relatively few feral colonies? Do they die from starvation, depredation or disease? What kills feral colonies?

Introduction

It can take a long time to understand complex natural phenomena. When you take into account geographic and seasonal variation you often end up with an explanation littered with more caveats than actual answers.

For example … do honey bees compete to the detriment of native solitary bees?

During May in an environment with limitless yellow acres of oil seed rape … probably not, but during early spring in an arable area with limited hedgerows … almost certainly.

OSR and threatening clouds

Sometimes the explanation may seem obvious, but isn’t. Bumble bees restrict themselves to field margins whereas honey bees venture hundred of metres into the middle of a field of OSR. Not only are there huge amounts of pollen and nectar available, but the different species exploit it in different areas of the field.

Not simple and not necessarily obvious 1.

Lost swarms

By many accounts, it’s been a very ‘swarmy’ season. The BBKA’s swarm line was swamped 2. Many beekeepers ran out of equipment (and no doubt patience) hiving swarms lost by beelosers with poor swarm control.

With ~250,000 colonies in the UK I wouldn’t be surprised if there were 50-100,000 lost swarms and casts.

That being the case, why aren’t there more feral honey bees?

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Lime time

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Synopsis : Lime, linden, basswood … a fickle source of excellent honey and a potential bee killer. When and why does the lime yield well and what explains the association of some trees with dead bees?

Introduction

There’s an early 20th Century faux castle near me with extensive ornamental gardens. These gardens – or, more accurately, the gardeners – are almost certainly responsible for the introduction of Rhododendron ponticum to the area. This is an invasive species and has spread east with the prevailing wind, blighting the environment, choking the life out of the near-unique temperate rainforest and providing me with an almost unlimited supply of firewood.

Rhododendron provide no nectar or pollen for honey bees in the UK, but are famous as the source of mad honey in Nepal. The local bumble bees do visit it, but I don’t remember seeing a honey bee on the flowers.

However, on a more positive note 1 those same gardeners also planted a row of lime trees along the road which are now a stately 30-40 metres high, in full flower and which can sometimes provide an excellent source of summer nectar.

Listen … you can hear it from here

Early on a calm July morning you can hear the insects buzzing in the canopy from at least 75 metres away … not just honey bees, but bumbles, wasps, flies, moths, butterflies and all sorts of other things as well. If we had hummingbirds here (we don’t) they’d probably visit the lime when it’s in flower.

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Supersedure

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Synopsis : Supersedure – the replacement of the queen without a brood break or a queenless period – is an important colony survival mechanism. How is it induced and can the beekeeper take advantage of it?

Introduction

Supersedure is the replacement of the queen – due to age or infirmity – by a new one reared in the same colony. Significantly the colony is at no point queenless, and may actually have two laying queens during the overlap period. Ted Hooper (in his Guide to Bees and Honey) states that 5% of colonies with two year old queens – at least of the strain of bees he used – actually have two queens in the colony in the autumn and they can often be found laying on the same frame.

I rarely inspect colonies in the autumn and have never seen two queens in a colony, let alone on the same frame. However, I’m well aware the process goes on undetected … or at least undetected until the following spring.

I’ll check a colony in mid-August and find the clipped, marked laying queen I expect. However, the following April – well before the swarm season starts here – I’ll find an unmarked and unclipped queen heading the colony 1.

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