Diverse mosaic environments within mountain village landscapes in northern coastal Taiwan
can simultaneously provide resources for human livelihood and support various habitats for wildlife
at low elevations. To achieve both sustainable use of resources and biodiversity conservation,
assessing and planning appropriate proportions of landscape composition in mountain villages is
of critical importance. To explore relationships between landscape variables and avian biodiversity
in mosaic landscapes of mountain villages, we conducted bird surveys in sample plots of different
forest-agriculture landscape mosaics in the Tamsui, Sanzhi, Shimen, Jinshan, and Wanli Districts
of New Taipei City in 2019~2021. Bird species were classified into different groups according to
3 functional categories (habitat preference, diet, and foraging stratum) and separately analyzed.
Results showed that the 100- and 300-m-scale landscape composition variables significantly affected
bird diversity and composition. Among them, forest cover was a key factor. Terrestrial total
bird species richness decreased with higher forest cover, whereas the richness of forest bird species
increased. In contrast, the richness of farmland, shrub and grassland, and general bird species,
the richness of bird species belonging to foraging strata other than the canopy, and the richness of
carnivorous, insectivorous, and granivorous bird species all gradually increased with decreasing
forest cover. Analyses of bird species composition also showed that most forest species, canopystratum
species, frugivorous/insectivorous species, and nectarivorous species occurred at sampling
plots with higher forest cover. In addition, numbers of endemic species in landscapes decreased
with decreasing forest cover. We estimated the threshold value of forest cover that may largely
alter the species richness of forest birds and found that forest bird species richness significantly
decreased when the forest cover was < 49.9% at the 300-m landscape scale. Therefore, we suggest
that retaining > 50% of forest cover in mosaic landscapes in mountain villages of northern coastal
Taiwan would help maintain bird diversity of forest specialists and might also support habitat conditions
for local endemic species.