Although many studies have investigated adaptations to heat stress, this study explored using observational data to determine how and when birds use a combination of both behavioural and physiological thermoregulation. The study focused on avian species' responses to high ambient temperature. Ambient temperature is a variable to which birds are particularly sensitive and which climate-change models predict will increase disproportionately rapidly in southern Africa's hot deserts, especially the Kalahari. The effect of ambient temperature on microsite use and foraging were analysed in order to investigate whether and under what conditions these forms of behavioural thermoregulation were used and by which species. The majority of ground-foragers made increasing use of shaded microsites as temperatures rose. This pattern was not apparent among strictly arboreal foragers because, even at high ambient temperatures, these birds are able to continue to forage in shaded and relatively cool microclimates. Species belonging to the guilds which forage at the ground surface are thus more vulnerable to having to make a trade-off between active foraging and seeking shade. The incidence of heat-dissipation behaviour was studied using three different combinations of observation times and resolutions. Under current conditions, the majority of species use evaporative cooling as a means of physiological thermoregulation, implying that the frequency and/or duration with which they will have to do this in the future may increase, elevating their vulnerability to climate change. Not all species responded to rising ambient temperatures in similar manners. Apart from ambient temperature, the variables explaining the response of heat dissipation are body mass, foraging guild and the interaction between ambient temperature and guild. The traits that predisposed species to being particularly vulnerable to high ambient temperatures were large body size and obligate ground-foraging. By contrast, the species that are most resilient to high ambient temperatures are arboreal insectivores – species whose diets are water-rich and whose foraging micro-habitats are largely shaded. It is these species which will be among the best adapted to the rising ambient temperatures predicted for the future. The study also aimed to determine the best practice for the observational study of heat dissipation. Based on the importance of detecting heat stress at low temperatures, a 30-second observation period (and whether or not heat-dissipation behaviour occurs at any time during this period) is recommended over instantaneous scans. The most labour-intensive method (of recording the time spent in heat-dissipation) adds little understanding to the binary response data.