How the map is made

The nectar flow map is an estimate: from public records it works out in which months of the year a place has nectar bees can collect. It does not look into hives, count bees or weigh honey.

Every value is against the place's own yearly peak: 100 is that place's best time; it does not compare amounts between places.

Back to the map

Step by step

  1. 1. Flowering records. PhenoVision (Dinnage et al. 2025, Zenodo 15306421, CC BY 4.0): about 30 million flower and fruit detections on iNaturalist photos, 1990 to March 2024, labelled by machine learning. Flower detections of bee-plant genera are counted month by month.
  2. 2. What a colony makes of it. Each genus is graded: a main honey source, medium, or minor. Sources below: the International Honey Commission's survey of European unifloral honeys, Sıralı (Beekeeping Research Institute, Türkiye), Pellett 1920 and named studies. A plant's value can change from region to region; where a regional source gives one it is used: goldenrod is a main fall source in the eastern US, but October, the asters' month, is a month of weight loss at every scale hive there (NASA HoneyBeeNet), so asters count as minor there; on the Canadian prairies both count as minor and the fall flow is left to the bees for winter (Alberta Agriculture).
  3. 3. Photographing effort. A month's value is the weighted bee-plant flowering against all plant photos taken that month, so a summer full of photographers does not read as a flow.
  4. 4. Documented flows. Forest trees and field crops hardly photographed (linden, chestnut, sunflower, cotton…) are lifted to the year's peak in the regions and months the sources give.
  5. 5. Crops. Rapeseed, mustard, sunflower and cotton areas from CROPGRIDS v1.08, their flowering from the GGCMI Phase 3 calendar (both CC BY 4.0) and extension-service rules.
  6. 6. Cold months. No flow in months whose days hardly ever average above 10 °C, nor in autumn months when a third of the nights freeze (NASA POWER temperature and frost normals, 2001-2020). Spring frosts do not end a flow: bees fly the next day.
  7. 7. Altitude and this year. Flowering is later above the region's mean height by Hopkins' law; this year's heat over the last three months moves the calendar earlier or later, and the end of the season only 40% as far as its start (Menzel et al. 2006: each degree brings spring 2.5 days earlier and delays autumn by 1 day). Between the tropics the rains set the season, and it is not moved there.
  8. 8. Pine honeydew. The honeydew season of the Aegean pine forests is added from its published phenology.

On top of the map

Migration report card. For a place and date: suitable when the flow holds at least moderate for 4 weeks, confidence is not low and the land is not bare; not suitable with no flow now or within 3 weeks; partly in between. Each reason is written on the card.

Collectable now. Where a flow is expected, the hours the weather lets bees fly: daylight, at least 12.2 °C, dry, wind under 8 m/s. Forecast from MET Norway (CC BY 4.0) at each cell's centre, every six hours.

Apiary site. Slope and aspect, high or low against the ground within 1 km (Copernicus elevation model), the region's winter wind (NASA POWER 2001-2020) and whether rising ground upwind breaks it.

Hornets and pests. GBIF records of the hornets and wasps that raid apiaries and of two notifiable pests (small hive beetle, Tropilaelaps mite): CC0 and CC BY only, placed to better than 25 km, kept as counts, latest year and months per 0.1° cell. For a place, the records within 50 km and the nearest one up to 300 km are shown. A record means "seen"; no record never means "absent". Most of France's Asian hornet records are published under a non-commercial licence and are missing. Rebuilt every quarter.

What ARIA cannot know

  • How much nectar really flows this year: drought, frost or a cold spring can stop a flow; the map knows the normal year and the last three months' heat and rain.
  • Plants nobody photographed: where few people go the records are thin, and the map says "low confidence" or stays blank.
  • Spraying, mowing, fields newly sown or cleared.
  • The strength of a colony, its diseases, how many hives are nearby.
  • The latest rules: they are shown from official sources, but ask the local authority before moving.