. Bonner zoologische Monographien. Zoology. JAHN, BIRD ClOMMUNITIKS OF THE ECUADORIAN CHOCO 40 30 5« a 20 10 run T, I IMN â all species ] MTW. J1 â 2- 5- 9- 17- 33- 65- 129- 257- 513- 1025- 2049- 4 8 16 32 64 128 256 512 1024 2048 4096 Body mass (g) FIG. 24. Proportion of species per body mass class in data sets gathered by standardized and non-standardized sampling (all species: n = 268), mist netting (MN: n = 135), and transect mapping (MTW: n = 187) at MNTl and MNT2. The log2 scale for the mass categories was selected in accordance with Terborgh et al. (1990: 225). For the Chi-squared test
. Bonner zoologische Monographien. Zoology. JAHN, BIRD ClOMMUNITIKS OF THE ECUADORIAN CHOCO 40 30 5« a 20 10 run T, I IMN â all species ] MTW. J1 â 2- 5- 9- 17- 33- 65- 129- 257- 513- 1025- 2049- 4 8 16 32 64 128 256 512 1024 2048 4096 Body mass (g) FIG. 24. Proportion of species per body mass class in data sets gathered by standardized and non-standardized sampling (all species: n = 268), mist netting (MN: n = 135), and transect mapping (MTW: n = 187) at MNTl and MNT2. The log2 scale for the mass categories was selected in accordance with Terborgh et al. (1990: 225). For the Chi-squared test I used the following combined groups in order to avoid the expected count of some cells in the contingency table being less than five: 2-8 g, 129-512 g, 513-4096 g (see text for details). (xl ~ , P < ). By contrast, no significant differences were found for the proportions within MTW data when compared with the complete set of species (xl = , P = ). The mist-netting surveys were strongly selective for smaller birds, as expected. Only species of the five lightest body mass categories ( 50% of all taxa in the course of the study. Species weighing 9-16 g were oddly overrepresented in the data set. On the other hand, the representation of taxa > 64 g de- creased continuously with increasing weight, and birds > 1025 g were not captured at all. By contrast, species detection in the MTW study was basically independent of body size, and at least 50% of the species present were recorded in all categories, the only exception being species > 2049 g. The latter group embraced only two rare non-breeding visitors, Sarcoramphus papa and Coragyps atratus (Appendix 6). For six of the nine body size groups detected by both methods, the medians of species recorded per survey were significantly greater in the MTW study than in the mist-netting project: 17-32 g (U = , P = ), 33-64 g (U = , P = ), 65-128 g (U < , P = ), 129-256 g (U
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