Field notes on novel bumblebee foraging behaviour in Short Rotation Coppice willow crop

From: Edie Jolley, PIE, Rothamsted, June 2007

11 June 2007 – Market Rasen, Lincolnshire

Whilst carrying out fieldwork in SRC willow on 11th June 2007, I saw two species of bumblebee workers (Bombus terrestris/lucorum and B. lapidarius) which were apparently feeding on honeydew residues on the willow crop. The willows were host to willow aphids (Tuberolachnus salignus?) and the honeydew they produced had collected on the branches and near the ground and become blackened (possibly with fungus). Bumblebees were observed ‘searching’ the ground around these deposits and feeding directly from them. One individual was seen to approach a colony of aphids and appeared to touch them or ‘buzz’ them causing the aphids to kick out their legs in characteristic fashion. It is possible this may have been a deliberate interaction between the species akin to the ‘milking’ of aphids by ants.

The two species observed have medium-length tongues (B. lapidarius) and very short tongues (B. terrestris/lucorum) and all appeared to be workers.

The weather was cool and damp and had been wet on previous days. The feeding bumblebees were seen near to the edge of the crop, but bumblebees had also been observed inside the crop that day.

Several individuals (B. terrestris/lucorum) were seen foraging on nearby white clover, but not in such numbers as on the honeydew, where approximately a dozen bees were seen. No bee on the honeydew was observed with pollen (see following).

21 June 2007 – Adwick le Street

B. terrestris/lucorum were again seen feeding on honeydew in SRC willow crop, at the edge of the crop and well into it. The observation was made on a 100m transect into the crop to count bees/butterflies. One individual was observed with full pollen sacks, indicating that feeding on the honeydew had not prevented normal foraging, although pollen collection may have occurred before the fortuitous find of honeydew. Many bumblebees were seen foraging outside of the crop on other flowers.

The honeydew in this crop was transparent and sticky (unlike in the previous crop where it was blackened). Honeydew had fallen onto other surrounding plants and a bumblebee was seen feeding from this (as well as from that on the bark of the willow itself).

The weather had again been damp, with rain over previous days, but was sunny on this occasion.


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