五色鳥在都市棲地的巢樹及巢位研究

五色鳥是1級洞巢者，除自行創造巢洞外，並為其他巢洞繁殖或居住的生物提供所需棲位，但是有關五色鳥天然巢洞的資料非常不足。本研究呈現5年間都市棲地五色鳥天然巢位的調查結果，包括2008~2012年繁殖季在台北植物園及周邊行道樹的五色鳥巢樹及巢洞資料。五色鳥使用多種樹種築巢，其利用巢樹的樹高、胸徑及1級、2級枝條數量的變異很大，巢洞位置之高度、樹(枝)徑亦有相當大的變化。樟樹大徑木最常被利用築巢，可能原因包括其為優勢種及木材爐乾比重適中(約0.4 g cm^(-3))。五色鳥利用生立木當巢樹為枯立木的4倍，可能與都市枯立木因安全因素被移除而數量受限有關；但即便築巢在生立木，五色鳥選擇的築巢部位絕大部分位於呈現腐朽狀態的主幹或枝條，意味樹木腐朽後有利五色鳥鑿洞。五色鳥最常在14~19 cm樹(枝)徑的位置築巢，約佔巢樹的1/2，顯示中徑級的主幹或枝條是五色鳥較傾向選擇的巢位徑級。在都市樹木管理上，應適度保留生立木的中徑級枯枝，以及中徑級的枯立木樹幹，以滿足五色鳥的巢洞需求，並且提供其他巢洞使用者繁殖或棲息的棲位資源。

關鍵字

五色鳥；洞巢者；枯枝；樹木腐朽；爐乾比重

並列摘要

Taiwan Barbet Psilopogon nuchalis is a primary cavity nester, and it creates niches for a variety of cavity-nesting and cavity-roosting organisms. However, information on barbet nesting in natural cavities is lacking. We present the results of a 5-yr study on natural nest-sites of the Taiwan Barbet in an urban area. The data, including descriptions of nest cavity trees and locations, were collected during the breeding seasons of 2008~2012 in Taipei Botanical Garden and its surrounding sidewalks. A variety of tree species and wide ranges of tree heights and tree diameters were selected by the barbets as nest trees. In nest trees, numbers of limbs of the first order had large ranges, as did those of the second order. Nest heights and tree (branch) diameters at nests also considerably varied. Large-diameter camphor trees Cinnamomum camphora were the major nest trees used by the Taiwan Barbet, for which the possible reasons might be camphor tree’s dominance and its moderate oven-dry specific gravity (i.e., 0.4 g cm^(-3)). Live trees with dead limbs were excavated by the birds 4 times as often as dead trees. One possible reason is that the number of dead trees in this urban area was limited, because some dead trees had been removed to prevent damage to people and their property. Although the Taiwan Barbet mostly used live trees as nest trees in this urban area, we found most of the cavities on decaying trunks or limbs of live nest trees. This fact indicated that the decayed part might facilitate cavity excavation by the birds. About half of nest sites had tree or branch diameters of 14~19 cm, which indicated that a barbet usually selected a medium-sized trunk or branch to make its nest cavity. When managing urban forests, it is recommended that medium-sized dead trees and medium-sized dead limbs on live trees be retained to meet the cavity needs of the barbet’s urban populations. Furthermore, the cavity resources will also benefit cavity-using communities in urban areas.

並列關鍵字

Psilopogon nuchalis ； cavity nester ； dead limb ； tree decay ； ovendry specific gravity

國際替代計量

五色鳥在都市棲地的巢樹及巢位研究

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