Use of nesting blocks by sixteen species of solitary bee in tropical lowland rainforest at La Selva Biological Station, northeast Costa Rica

Published source details

Thiele R. (2005) Phenology and nest site preferences of wood-nesting bees in a Neotropical lowland rain forest. Studies on Neotropical Fauna and Environment, 40, 39-48.

Background

Many bee species rely on pre-existing cavities in dead wood or plant stems for nest sites. The availability of these nest sites can be augmented using nesting blocks with pre-drilled holes. This study demonstrates the use of nesting blocks (trap nests) by sixteen bee species in tropical lowland rainforest in Costa Rica.

Action

24 hardwood nesting blocks were set out between August 1998 and July 1999. Each block was 70 x 4.5 x 10 cm, and had 80 drilled holes, 6.5–9 cm long, with 20 of each of four diameters (6.5, 8, 11 and 13 mm).

Two nesting blocks were set in each of six dead and six live trees – one at canopy level 23-37 m high and one 1.5 m above the ground. Five canopy nesting blocks in dead trees were left in place for a further 12 months, until July 2000. Canopy nesting blocks were suspended from 4 mm nylon cords hanging over branches and high enough to be exposed to sunlight for most of the day. All the trees used were in an area of 730 ha of mostly old growth forest.

Once a month, all blocks were collected after dark and exchanged for empty blocks. When collected, the hole entrances on the nesting blocks were covered with plywood. The following morning, all adult bees in the holes were identified, and nests counted.

Consequences

Sixteen bee species used the nesting blocks, of which six made more than ten nests over the study period. Of these, Centris analis (161 nests), C. bicornuta (58 nests), C. labrosa (57 nests) and Tetrapedia maura (47 nests) used only 6.5 and 8 mm holes. Centris vittata (77 nests) and Duckeanthidium thielei (33 nests) used only 11 and 13 mm holes.

In the first year of the study, 69.3% of all nests were found at canopy level in dead trees. Blocks in dead trees had more nests (73.6% of all nests) than those in live trees (26.4% of nests) and canopy nest blocks had more nests (86.3% of nests) than those at 1.5 m (13.7% of nests). Authors stress the importance of retaining dead standing emergent trees for bee conservation in this habitat.

Exceptions to this pattern were that D. thielei nests were mostly found on living trees, and C. labrosa nests were found in similar proportions at both heights.

Note: If using or referring to this published study, please read and quote the original paper. This can be viewed at: http://www.tandf.co.uk/journals/NNFE