Climate Change Vulnerability Assessment (CCVA) is a widely applied approach to guide species conservation under climate change. The framework of CCVA usually includes three dimensions－exposure, sensitivity and adaptive capacity. Among which, species sensitivity relies on certain assumptions about biological traits, such as species with larger body mass or smaller clutch size are more vulnerable. However, these basic assumptions are likely to vary across taxa and ecosystem. Obtaining prior knowledge before conducting CCVA is necessary. We used Breeding Bird Survey data in Taiwan to investigate whether dynamics of bird populations can be explained by climatic variation and whether changes of bird populations are associated with ecological traits, including body mass, clutch size, and diet types. We found that species showed different sensitivity to temperature and precipitation and up to 47% were not responding to climatic variation. Ecological traits showed opposite predictions in that species with larger body mass or smaller clutch size were increasing. Our study suggests that the general assumptions applied in CCVA may oversimplify species responses to climates. Local biodiversity monitoring scheme can play an important role to acquire appropriate information to assess species vulnerability under climate change.