Preliminary investigation on nest-tree and nest-cavity characteristics of the Taiwan Barbet (Megalaima nuchalis) in Taipei Botanical Garden.

Abstract

Taiwan Barbet (Megalaima nuchalis) is the only species of the Ramphastidae found in Taiwan and is endemic to the island. Megalaima nuchalis is found at low to mid elevations and is typically seen in the mid-canopy layer of broadleaf forests. During the breeding season, M. nuchalis excavates its own nest cavity in tree trunks or branches; therefore, it is closely associated with forests. From March to September of 2008, we investigated the characteristics of nest trees and nest cavities of M. nuchalis in Taipei Botanical Garden (TBG). The measured variables were nest tree species, tree height, tree diameter at breast height, nest height, tree diameter at nest, diameter of the cavity entrance, length of the horizontal passage, depth of the hole, and orientation of the cavity entrance. In total, we found 27 nest holes in 12 trees, which included 8 different tree species dominated by camphor (Cinnamomum camphora (L.) Presl). Megalaima nuchalis excavated nests in dead trees or in dead branches of living trees, and very few of the nest trees were monocotyledons. The nest cavities were found either on the main tree trunk or on side limbs, and the nest locations seemed to be related to the location of dead limbs on the nest tree and nest tree height. The shape of most cavity entrances was almost circular, and the size corresponded well to the body size of the birds themselves, as this prevents the invasion by natural enemies. The cavity entrances were mainly orientated towards the northwest to southwest, as these directions might have good air flow and could keep the nests well-ventilated and dry. The removal of dead trees and dead limbs from M. nuchalis habitats is disadvantageous during their breeding season. We recommend preserving dead trees and dead limbs which pose no danger in urban green areas as they provide nest cavities and resting holes for M. nuchalis and other secondary cavity nesters-in order to maintain and even enhance urban animal biodiversity.