In this study, 4 seasons of bird communities were surveyed in Danongdafu plantations, Hualien
County when the plantations were 6~7, 9~10, and 15~16 yr old. Birds were classified according
to their forest dependency as forest specialists, forest generalists, forest visitors, or other nonforest
users. Birds in the former 2 and the latter 2 types were respectively categorized as forest and
non-forest species. Results showed that averages of the number of species, the number of individuals,
and the Shannon-Wiener diversity indices of the forest specialists significantly increased as
the plantations grew older. In other words, averages of the number of species, the number of individuals,
and Shannon-Wiener diversity indices of the forest specialists in 15~16-yr-old plantations
were significantly higher than those of 9~10-yr-old plantations, and averages of the number of species,
the number of individuals, and the Shannon-Wiener diversity indices of forest specialists in
9~10-yr-old plantations were significantly higher than those in 6~7-yr-old plantations. The Shannon-
Wiener diversity indices of forest specialists and forest generalists increased with the growth
of the tree biomass. It was speculated that the growth of tree biomass has a significant effect on the
diversity of birds, especially forest birds. In addition to the increasing diversity of birds, the compositions
of birds in the 3 time periods also differed. Based on contributions of representative bird
species to the similarity of communities, the bird community in 6~7-yr-old plantations was dominated
by non-forest birds, such as Lanius schach and Phasianus colchicus, which often appear on
open land and in the ecotone between farmlands and forests. In 9~10-yr-old plantations, the major
group of the bird community had transformed into forest birds. In 15~16-yr-old plantations, only
1 non-forest user, Dicrurus macrocercus, had a greater influence on the community composition,
so the trend of forest species replacing non-forest species was clear. However, the bird community
structure of 15~16-yr-old plantations still greatly differed from that of an adjacent secondary forest,
the avian community of which was dominated by forest birds. It was speculated that canopy
closure and frequent understory weeding might lead to less herbaceous, shrub, and native tree
species. Thus, it might be difficult for the plantation to succeed toward a secondary forest. Hence,
the plantation had a different bird community from the secondary forest. From the perspective of
promoting biodiversity, the succession of a plantation toward a secondary forest should be able to
harbor greater bird diversity. In summary, the variation in bird diversity in plantations showed an
upward trend. The composition of bird communities may continue to change with changes in the
forest structure and species composition. It is suggested that in the future, time series and spatial
analysis be used to explore bird changes in plantations.