Low Winter Mortality of Dutch Bee Colonies
Last winter, beekeepers generally lost fewer bee colonies than in the years before. The national mortality percentage has been established at 9.2%. This is the outcome of a telephone survey among beekeepers carried out by the Dutch Beekeepers Association (NBV) and Wageningen University & Research centre (UR) on Tuesday 8 April.
Winter mortality of bee colonies has been alarmingly high for years. In some winters one in four colonies did not survive. The survey after the winter of 2012-2013 showed that mortality had decreased to about 13%. “These results are encouraging but it is too early to consider this as a trend”, says Bram Cornelissen of Wageningen UR.
The survey was held among members of the NBV, with over 6000 members the largest beekeepers association in the Netherlands. Members of the General Dutch Beekeepers Association (ANI) were involved in this survey as well. Together these two associations represent about 90% of the beekeepers.
To establish the winter mortality percentage the telephone panel asked beekeepers how they – in autumn – had prepared the colonies for winter and how many of these colonies were still alive at the start of spring. A total of 210 randomly selected beekeepers from the membership files were asked for the mortality of the bee populations over the last winter, from which a winter mortality of 9.2% (confidence interval 95%: 7.2% – 11.7%) was calculated; 69% of the respondents indicated to have had no colony mortality.
At this moment it is still unknown why winter mortality over the last two years was lower than in the years before. Although the mild winter is suggested as possible explanation, this is not plausible because the severe winter of 2012-2013 also showed a relatively low mortality rate.
This year’s low winter mortality does not mean that the end of the mortality problems of bees is near. Bee mortality received a lot of attention over recent years. The beekeepers themselves are playing a major part with good preparation of bee colonies for winter. This may now be bearing fruit. Favorable environmental conditions, however, are equally important for a healthy bee population.