In tropical and subtropical forest ecosystems, cavities formed by decay processes are a key but scarce resource for birds that nest and roost in them, which makes them a highly sensitive group to logging. The piedmont forest of northwestern Argentina is a complex ecosystem with 113 tree and 120 bird species. It has high logging pressure on the few, well-conserved forest remnants, complicating the delineation of sustainable management guidelines for each tree or bird species in a short time. Our objective was to reduce the complexity of subtropical forests by grouping tree species according to the characteristics used by secondary cavity-nesting birds (i.e. non excavators). In the piedmont forest, 50 plots of 0.25 ha were sampled to record cavity trees and cavity characteristics. These were then used in a cluster analysis to form tree groups. Additionally, cavities were searched to identify the bird species using the decay-formed cavities. A total of 187 cavity trees, comprising 23 tree species, were recorded, and these formed four tree groups or clusters. We recorded 86 cavities that were used by secondary cavity-nesting bird species. The four tree groups were unequally used by secondary cavity nesters. The tree group that included valuable timber species (Myroxylon peruiferum, Anadenanthera colubrina and Calycophyllum multiflorum) and had the greatest cavity availability represented 71% of total cavity use. Another tree group with valuable timber species (Cedrela balansae and Amburana cearensis), measured > 73 cm DBH and > 21 m tall, had cavity entrances > 0.10 cm², and contributed 14% of all cavity use by birds. A third group had no highly economically valuable tree species, and included the snag category (i.e. standing dead trees) as well as a 15% of cavity use. The fourth tree group had a DBH < 0.40 cm, only one highly economically valuable tree species (Cordia trichotoma), and supported no cavity use. The clustering of subtropical trees can reduce the complexity of these forests, hence easing their management by focusing on those groups with tree species showing similar characteristics and providing suitable nesting sites for secondary cavity-nesting birds.

在热带和亚热带森林生态系统中，腐烂过程形成的空洞是在其内筑巢和栖息的鸟类的关键但稀缺的资源，这使它们成为对伐木高度敏感的群体。阿根廷西北部的山前森林是一个复杂的生态系统，拥有113种树木和120种鸟类。它对少数，保存完好的森林残余物具有很高的采伐压力，这使得在短时间内确定每种树木或鸟类的可持续管理准则的工作变得复杂。我们的目标是通过根据次级洞巢鸟类（即非挖土机）使用的特征对树木物种进行分组来降低亚热带森林的复杂性。在山前森林中，采样了50个0.25公顷的土地，以记录空腔树和空腔特征。然后将它们用于聚类分析以形成树组。另外，使用蛀蚀形成的腔来搜索腔以识别鸟类。总共记录了187棵空洞树，包括23种树种，它们形成了四个树群或簇。我们记录了86个蛀牙，它们被次级蛀牙鸟类使用。次生巢穴不平等地使用了这四个树组。包括有价值的木材种类的树群（Peryiferum，Anadenanthera colubrina和Calycophyllum multiflorum）具有最大的蛀牙利用率，占整个蛀牙使用量的71％。另一个树种有价值的木材树种（Cedrela balansae和Amburana cearensis），树高> 73厘米DBH，树高> 21 m，洞入口> 0.10 cm ²，占鸟类使用的洞总数的14％。第三类没有极具经济价值的树种，包括障碍物类别（即死树）和15％的树洞使用率。第四类树的DBH <0.40 cm，只有一种极具经济价值的树种（Cordia trichotoma），并支持不使用腔体。亚热带树木的聚类可以降低这些森林的复杂性，因此通过关注那些具有相似特征的树种并为次生巢穴鸟类提供合适的筑巢地点，可以简化其管理。