To date, 90% of tropical montane cloud forest (TMCF) in the northern Andes has been destroyed yet descriptions of avian community structure are largely limited to biodiversity inventories. In contrast, lowland rainforest (LRF) communities have been the subject of four studies that show LRF communities are marked by high α-diversity, a large number of rare species, large territory sizes, and highly patchy species distributions when compared with forests in temperate latitudes.
Recent work by Kattan and Beltran (2002) suggests that territory sizes and densities of the terrestrial insectivore guild may resemble communities in temperate forests far more than LRF. Many other studies document lower species richness for TMCFs. Such information raises the question: does community structure in TMCF follow patterns generally attributed to Neotropical communities on the basis of work done in LRF, or is it fundamentally different?
Following studies in LRF, I used intensive spot mapping to plot all territories of understory and terrestrial insectivores in a Peruvian TMCF. I then compared my data on species richness, territory size, density, patchiness and biomass to communities in LRFs.
Results/Conclusions
Data from a 26.2 ha plot in a relict TMCF on the western slopes of the Andes show that understory and terrestrial insectivores have mean territory sizes of (nspecies = 3) 0.87 ± 0.68 ha and (nspecies = 6) 1.64 ± 1.35 ha, respectively, and corresponding densities of (nspecies = 3) 0.51 ± 0.28 and (nspecies = 7) 0.46 ± 0.28 pairs/ha. Such territory sizes are about one seventh of those reported in LRF and roughly correspond to values obtained in Colombian TMCF. Half (50%) of the 10 species on the plot occupy less than 50% of the area, which almost exactly matches patchiness in LRF; however, none have fewer than 3 territories and thus are not considered “rare.” Biomass of the terrestrial insectivores was 2271 g/10 ha, over four times that of the guild’s biomass in LRF and approximately the same as the biomass of the Grallaria spp. that compose most of the guild in Colombian TMCF.
My results indicate that bird communities in TMCF have communities with markedly different structure from those in LRF, particularly considering species richness, territory size, density, and the biomass of terrestrial insectivores.
