Bryophyte Use in Bird Nests Varies with Nesting Location in a Tropical Montane Forest

Bryophytes serve as nest material for many temperate bird species, yet their role in tropical avian ecology remains poorly studied despite high bryophyte and passerine diversity. In this study, we quantified bryophyte use as nest material by passerine birds at Doi Inthanon National Park, Thailand, over one breeding season. We observed 47 nests from 22 species to contain bryophytes, of which 26 nests from 15 species were sufficiently complete for quantitative analysis. The mean proportion of bryophytes by dry weight was 0.513 ± 0.278 across all nests, with no significant overall preference for bryophytes over other materials. Of the three bryophyte groups identified, pleurocarpous mosses significantly dominated, comprising 0.851 ± 0.156 of the bryophyte proportion (p < 0.001). Beta regression model selection identified nest location as the strongest predictor of bryophyte use, the pseudo-R2 value of 0.21 indicated a modest improvement from the null model. Tree-nesting species used a significantly higher proportion of bryophytes than ground-nesting species (0.60 ± 0.26 vs. 0.32 ± 0.23; p = 0.011). This study did not quantify ambient bryophyte availability surrounding nests, precluding differentiation between active avian selection and passive resource-driven material use. Our results highlight the importance of preserving intact forest canopies to maintain bryophyte–bird interactions in tropical montane ecosystems. Canopy loss may reduce epiphytic pleurocarpous moss resources and alters nest material composition for arboreal passerines, affecting breeding microhabitat conditions.