We review evidence for whether and why mountain birds are potentially more vulnerable to climate change than birds at low elevation, given current knowledge of the avian limits to physiological and environmental conditions. The observed impacts of climate change on bird populations, communities and distributions in mountain environments are limited.  We summarise these responses and provide an assessment of the main mechanisms that might underpin those changes, such as changes in climate (temperature, precipitation, snow cover extent), and biotic drivers (phenology/food mismatch, prey/predator populations, shifting treelines). The potential future impacts of climate anticipated in mountain environments, considering the vulnerability of montane species and the likelihood of increasing upslope colonisation by species that currently occupy lower elevations, are considered, including a comparison between the observed and projected impacts where available.  Finally, we discuss potential conservation actions for mountain birds in the face of climate change.  Are there ways that the management of these habitats can be altered to either help vulnerable species resist negative impacts, or to facilitate more positive changes in response to climate change? We conclude by summarising anticipated avifaunal community composition and function in these mountain environments by the end of the century.