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  • Writer's pictureNigel Costley

Now is the Winter of Our Discontented Bees

With nearly a third of all registered beekeepers taking part, New Zealand’s Colony Loss Survey is in a league of own, compared to other similar surveys carried out all over the world. NIGEL COSTLEY caught up with those behind the world-leading concept to find out how it came to be and how beekeepers’ high levels of participation is creating a valuable resource, for now and the future.

It’s a doddle really. It took me just10 minutes to fill in last winter’s Colony Loss Survey.

Admittedly I had a simple operation of only three quite small apiaries, but this ease of use helps to explain why New Zealand’s survey has the highest participation rate (32% of all registered beekeepers) among the 30 countries involved by some margin.

Pike Stahlmann-Brown, the architect of New Zealand's Colony Loss Survey.

Alarmed by high winter beehive deaths to such mystery diseases as Colony Collapse Disorder, beekeepers world-wide have joined forces to monitor and analyse these losses. Many factors are at play: diminishing range of bee forage, disease incursion, beekeeper practices, and the use of agricultural chemicals. The accumulated effect of these factors is largely unknown.

Centered in the University of Bern, Switzerland, COLOSS (Honey Bee Research Association) was formed to standardise the surveys so the data can be studied and compared internationally.

Through the agency of Manaaki Whenua, Landcare Research joined this scheme in 2015 with its own annual loss survey. New Zealand has adapted the COLOSS survey to suit its own needs, so ours is not strictly a COLOSS survey, hence the name NZ Colony Loss Survey. Using the tools of econometrics, the survey’s designer and director is Landcare Research’s principal economist, Pike Stahlmann-Brown.

“If statistics is about describing data in a useful way, then econometrics can be thought of as a sub-field that is especially concerned with causality,” he says.

Once collected, the survey’s data is then presented in pie graphs and histograms, which show at a glance the frequency in percentage terms of each factor under scrutiny.

As the survey is internet-based, huge quantities of data can be collected and new lines of enquiry pursued that would be completely unworkable in a paper-based system. The widespread up-take of the survey has implications beyond the statistical appeal of dealing in big numbers. It is a reflection of a broad-range of beekeepers’ views and experiences.

“These days there’s the danger of an echo chamber effect – only like-to-like groups talking to each other, but this opens up information from the whole beekeeping community,” Stahlmann-Brown says.

How the Survey has developed

When the survey was launched six years ago it followed the international pattern, but the researchers quickly realised the need to adapt it to New Zealand conditions, such as accounting for giant willow aphid, which isn’t an issue in other countries. Certain core questions have been retained in order to make valid international comparisons, but many questions have been ‘Kiwi-ized’ to reflect our environment and follow up on the participants’ answers. Hence the 2020 survey drills down into the reported causes of death in much greater depth. There are only six extra questions though, so the survey is still quick and easy to do.

While the ultimate goal is to find the cause of hive death, a considerable amount of background data has to be collected too, including regional location, size of operation, environmental conditions, type of honey flow, and various beekeeping procedures.

In discussing the different categories of hive death attributed by beekeepers, the researchers are at pains to stress these are the perceived causes. We all know that even with a very thorough inspection, it is often unclear exactly what killed a particular hive. In attributing cause of death, queen problems and varroa are by far the most commonly reported factors. Evidence can be deceptive though, an irregular brood pattern, for example, can be caused by nosema as well as a defective queen.

From Question One

The survey begins by clearly identifying who is filling in the questionnaire – owner or apiary manager. The survey suggests that ideally it is the apiary manager that does the survey for the hives they have handled. It then asks for the email address of those managers so they can be approached directly to complete the survey, a potentially important issue in the accuracy of reporting for a big operation.

As queen problems are implicated as the greatest cause of hive death (3.7% of all hives surveyed), this topic is now covered in more detail. For instance, did your hives go into winter with a new (autumn) queen? Did you use breeder queens or did you raise them yourself? Even the method of re-queening – cage or cell – is explored.

“For this part we needed to talk to the queen breeders to ensure we got the language right,” Stahlmann-Brown says.

After queen issues, varroa is the next most commonly attributed cause of death (3.5%), so there are several questions seeking specifics on mite monitoring, and treatment regimes.

The next most common attributions of death is starvation. Wasps and robbing are under 1%, and suspected death from chemicals is infrequently reported (0.1% of all hives surveyed).

There are questions on feeding and supplements and you can record any apiaries that you think were compromised by over-crowding. The survey concludes with a snapshot of the participants’ experience, training and most importantly, their source of technical information – questions which have been included, in part, to augment a similar study being undertaken in Europe.

Improving Beekeeping Practices

There is some anecdotal evidence that the survey is improving beekeepers’ record keeping, Stahlmann-Brown says.

“A very large beekeeping operation has changed how they record their own data to more closely follow the survey because they found it a useful way to categorize losses.”

Even the prospect of filling in the survey should make beekeepers more perceptive and careful in recording their observations.

Once the data is collected and the survey closes in early November, algorithms looking for outliers are produced. In trying to find the story for that particular season there are ongoing conversations with beekeepers, particularly with those who throw up strikingly unusual results.

By late January, with the follow-ups completed, a draft report is written. Considerable work is required to get the graphics presentable and the survey is published in autumn after close vetting.

Where to from here?

The questionnaire will continue to evolve, going even deeper into such issues as varroa monitoring. So promising is this line of enquiry, that New Zealand’s questions may be adopted by other countries.

As to interpretation of the results, there are a couple of scientific papers in the works.

“Phil Lester (of Victoria University of Wellington) has a new PhD student who will be using anonymised survey data to follow trends. She’ll be looking at varroa in particular, which I think is the perfect use for data like this,” Stahlmann-Brown says.

All six annual surveys taken since 2015 can be found on the Landcare Research website. They can be easily accessed, read, discussed with colleagues and compared to a beekeepers own situation.

There’s a lot of information to grapple with and analysing the results would make a great ‘citizen science’ initiative for a bee club where trends are explored and promising leads followed up. The worse that could happen is a few wild goose chases, but it would encourage evidence-based discussion of bee health.

New Zealand’s Colony Loss Survey provides a sturdy baseline which would be vital in gauging the effect of any radical changes, such as the incursion of a new pathogen. Whatever else, given the expertise of those involved and continued beekeeper compliance, the survey provides valuable knowledge to combat whatever the beekeeping gods throw at us.

Results of the 2020 Colony Loss Survey can be found here.


Given the enormous variation in beekeeper practices and environments, comparisons with other countries comes with a caution. Each country has its particular advantages and disadvantages. You could say New Zealand is lucky in that we don’t yet have some of the pests and diseases found in other countries. While other countries may not have some of the adverse factors faced by Kiwi beekeepers, such as regions of over-crowding.

On this basis our losses are better than the EU average of 14.5% and the participation rate is in a class of its own.

However, our performance has deteriorated. The overall winter loss for 2020 was 11.3%, meaning NZ lost approximately 99,150 colonies. This loss rate is statistically higher than at any time since winter colony losses were first measured in 2015. Had loss rates persisted at 2015’s lower levels, researchers estimate that there would have been 25,709 fewer colony deaths during winter 2020.

Americans have suffered some of the worse winter losses in recent years – over 30% – but their system reports the whole year’s loss, both winter and summer. On the face of it this seems a good idea, in that spring losses are not accounted for in our system and beekeepers frequently claim they can be more severe than winter losses. However, the American system created added confusion in the simple business of defining the change of seasons in a country with such huge climatic variation.


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