August Nectar Shortage Threatens Honeybees, Study Finds

In late July and August, honeybees face their most difficult foraging season of the year. They expend more energy flying and walking in search of nectar while collecting less of it, a mismatch that researchers at the University of Sussex have now documented with precision for the first time. The study, published in the British Ecological Society's journal Functional Ecology, measured the energetic cost of foraging against the actual nectar gained across the active season, revealing a stark seasonal pattern that has profound implications for how we manage the landscapes where bees live.

The researchers conducted their work in green spaces across Brighton and Edinburgh, observing honeybees from April through October and collecting foraging data from 1,217 individual bees. They also measured nectar content from 1,426 flowers. What they found was consistent between the two cities, separated by roughly 600 kilometers: late summer is when bees struggle most. The culprit is straightforward—fewer flowers bloom in late July and August, and the pollinators that do venture out face intense competition for what little nectar is available. Spring presents the opposite picture. When horse chestnut, willow, and cherry trees flower, honeybees find abundant resources and forage with maximum efficiency.

The timing of this shortage is particularly consequential because late summer is when most pollinator species are most active and most in need of food to provision their offspring. Dr. Nicholas Balfour, one of the study's authors, emphasized that this seasonal crunch represents a critical vulnerability. The research adds to growing evidence that late summer poses a genuine bottleneck for pollinator survival, one that becomes more acute in years when heatwaves reduce nectar availability in flowers and disrupt normal flowering patterns.

The solution, according to the researchers, lies partly in changing how we manage our green spaces. Rather than removing late-summer-blooming plants that many consider weeds, allowing them to flourish could provide essential food when bees need it most. Thistle, ragwort, and knapweed—plants typically mowed down or pulled up—bloom precisely when honeybees are struggling. Planting late-summer flowers deliberately, adjusting lawn-mowing schedules to preserve blooms, or simply tolerating these plants could bridge the gap. Dr. Ciaran Harris noted that such interventions would be especially valuable in an era of climate disruption, when heatwaves and shifting flowering times compound existing pressures from agricultural intensification.

The research method itself represents a methodological advance. Rather than relying on indirect measures—such as decoding the waggle dances bees perform to communicate foraging locations—the team directly observed and measured the energetic equation. They timed how long bees spent flying and walking during 60-second observation periods, then cross-referenced this against the nectar yield from specific flowers they visited. Professor Francis Ratnieks noted that this direct measurement confirmed patterns that had emerged from years of indirect studies in the lab, lending confidence to the findings.

One limitation of the study is its geographic scope. By examining only green spaces in two cities, the researchers could not assess how different land-use patterns—farmland, gardens, urban development—influence nectar supply throughout the year. Follow-up work will be needed to understand whether certain land types, such as private gardens or farmland managed under agri-environment schemes, naturally provide nectar during the late-summer gap. The implication is clear: the problem is real, the solution is within reach, but the full picture of how to implement it at landscape scale remains incomplete.