Preliminary analysis of the 2019/2020 COLOSS survey – by Dr Mary Coffey & Dr John Breen

Preliminary analysis of the 2019/2020 COLOSS survey – by Dr Mary Coffey & Dr John Breen


The annual COLOSS survey of winter colony losses comes at the end of the winter and the beginning of the new beekeeping season. The survey which uses a standardised questionnaire was originally developed in 2008 by the COLOSS monitoring group. The same basic questionnaire has been used since the beginning; sometimes the wording of the questions has been tweaked to remove ambiguities, sometimes a new question has been inserted, but it is the same basic questionnaire since the beginning.

This year’s version is in the middle pages of this issue of An Beachaire. Irish beekeepers have been involved in the COLOSS survey since 2008. Internationally, 35 countries now participate in this annual Survey.

The national datasets are submitted to central COLOSS network for analysis. Before doing that, the names and addresses of individual responses are changed to a latitude-longitude location. In addition to reporting winter loss rates in each country, the international analysis of the full dataset from all participating countries allows possible causes for the losses to be identified.

The first few questions aim to quantify actual winter losses. The other questions aim to investigate possible reasons for the losses. Hence it is critical that prior to completing the survey, each beekeeper assesses their own colonies and make notes. The more accurate the information supplied by the beekeepers in relation to the status of colonies post winter, the more reliable the outcomes from statistical analyses of the possible causes of these losses.

The Survey has considered the effects of operation size, migration, six specific forage sources and queen age/requeening on winter colony mortality and have been published in peer reviews articles in the Journal of Apiculture Research (Brodschneider et al. 2016, 2018; Gray et al. 2019).

These articles are “open access” and can be freely downloaded. In future years additional possible causes of winter colony mortalities will be examined, for example, Varroa treatment/management methods. To ensure that the Irish dataset continues to be included in these international analyses and the outputs remain relevant to Irish beekeeping, it is critical that additional beekeepers complete this year’s survey, and that all participating beekeepers complete all questions. If some questions are not answered, those responses are sometimes dropped from the overall analyses.

The international analysis of the last years’ data (2019/2020) has been completed and a peer reviewed article is presently in press. However, this is a preliminary analysis of the Irish dataset from the 2019/2020 Survey. 374 Irish beekeepers completed the 2019/2020 survey.

This represents approximately 11% of the beekeeping community. This is a slight decrease (approximately 2%) in the response rate from previous years, however it is still be considered representative of beekeeping in Ireland. And it was completed under Covid-19 limitations. Geographically, beekeepers from all counties were represented (Figure 1). However, there were ten counties with fewer than ten responses, and we hope to improve on that this year.

Figure 1

The national average winter losses experienced by beekeepers in Ireland 2019/2020 was 18.1%. This is higher than the 15% winter losses which we have considered “acceptable” losses and much higher than the winter losses experienced by beekeepers during the previous winter (2018/2019) (10.6%: Figure 2).

Figure 2

The total winter losses experienced by beekeepers were subsequently divided into three broad categories (Figure 3):

– died out (or reduced to a few hundred bees) during winter
– died out due to natural disaster
– was still alive post winter, but had queen problems that could not be solved (drone laying queens or had no queen at all).

Beekeepers reported that 7.1 % of the total dead colonies died due to queen problems, 10.3% had just died out during the winter period, while 0.04% died due natural disaster. In the Irish context natural disasters refers to flooding, wind, fallen trees, cattle/sheep, vandalism, and theft.

However, the low percentage losses being attributed to natural disasters, which is like last year, suggests that like beekeepers in many parts of Europe and in the US, Irish beekeepers consider natural disasters as not important in causing winter colony losses.

In contrast, Irish beekeepers consistently perceive queen problems as one of the main contributing factors to increased winter colony losses and this fluctuates from year to year. For example, in 2016/2017, 2017/2018, 2018/2019 and again in 2019/2020 colony losses being attributed to queen problems were estimated by beekeepers as 8%, 9%, 6.4% and 10.3% respectively.

This is relatively high compared to the loss rate estimated for the overall international study which has consistently reported loss rates from queen problems relatively constant at 4 to 5%. Figure 3 indicates the clinical symptoms reported by beekeepers in the dead colonies and their perception on the possible cause of the colony dying out during the winter period.

Figure 3

Once the international analysis of the data is published it will provide more details on winter colony losses experienced by beekeepers in 2019/2020.

Brodschneider and multiple authors. Journal of Apicultural Research, 55: 375-378.
Brodschneider and multiple authors. Journal of Apicultural Research, 57(3), 452-457
Gray and multiple authors. Journal of Apicultural Research 58(4), 479-485.

The COLOSS 2020/2021 Survey is NOW OPEN for submissions. 

Click here to participate.