A list of tree species in the study area large enough to contain a hornbill nest
was compiled (Poonswad 1995, Chimchome et al. 1998; Table 3). Of 25 candidate
species, only two (T. nudiflora and Ailanthus grandis) were used for nesting in the
study area. Both were emergent softwoods with large girth, relatively common,
with T. nudiflora the most common. Of 11 other softwood species (Table 3),
no large trees of seven species were recorded in the plots; the remaining four
combined were uncommon (1.14 trees/ha). Of 25 potential nest species, large
trees of 16 species were available at 5.9 trees/ha, with the two recorded nest
species comprising 1.33 trees/ha and no large trees of the remaining nine species
being recorded in the plots (Table 3).