Sampling butterflies in tropical rainforest: an evaluation of a transect walk method

An adapted version of the 'Pollard walk' is frequently used in tropical rainforest to assess the abundance and diversity of butterfly species. Data from a study of primary and secondary forest in central Kalimantan, Indonesia, were used to test the applicability of the method and its limitations. Transect walks were more efficient than kite netting in accumulating individuals and species. However, the problem of distinguishing species within some tropical butterfly genera on the wing may prove a limiting factor. Less than 50% of individuals recorded using transect walks were identified to species, with four genera responsible for 87% of individuals not identified to species. The question of whether transect walks can be used to compare interspecific abundance at one site or intraspecific abundance between sites remains to be tested conclusively. In the absence of independent validation of the relationship between transect counts and population sizes, inter-site differences in visibility and interspecific differences in activity and behaviour may distort comparisons.