(Table S1.3) Bird functional traits of winter residents, winter visitors, summer residents and summer visitors of 36 study islands in the Thousand Island Lake, China

Two habitat-associated traits (vertical and habitat specificity), one dispersal-associated trait (movement capacity) and body mass (linked to both habitat and dispersal) were chosen as predictors to test for correlations with species occupancy frequency. Body mass (g) was measured as the mean body mass of multiple adult individuals. Movement capacity was an index of each species' mobility, and calculated as mean wing length (mm) / cube-root of body mass. Vertical specificity was quantified as ground (score 1), understory (2), midstory (3), and canopy (4) for each bird species. Habitat specificity was the number of habitats used by a given species, ranging from 1 to 7.