Combining individual tracking data with high-resolution thermal mapping to identify microclimate refugia for a threatened grassland bird

Abstract

Abstract Context Local microclimate refugia may buffer against detrimental effects of extreme temperatures preventing fitness loss. Objectives By combining high resolution habitat and climate information with GPS tracking data, we develop a novel approach to identify the use and availability of cooler microclimate refugia within large landscapes. Methods GPS data from 77 little bustards (Tetrax tetrax), an endangered grassland bird tracked between 2009 and 2019, was combined with hourly temperature information at 30x30m resolution. 92,685 GPS locations and their surrounding 500m areas were characterised with temperature and habitat information and used to determine the availability and use of microclimate refugia (sites > 0.5˚C cooler than the surrounding landscape). Results We found that the semi-natural grassland landscapes used by little bustards have limited availability of cooler microclimate areas – fewer than 30% of the locations provided microclimate refugia opportunities. The use of cooler microclimate sites by little bustards increased at higher ambient temperatures, suggesting that individuals actively utilise microclimate refugia to cope with extreme heat conditions. Microclimate refugia availability and use were greater in areas with heterogeneous vegetation cover, and in coastal areas. Conclusions This study identified the landscape characteristics that provide microclimate opportunities and shelter from extreme heat conditions. Little bustards made greater use of microclimate refugia with increasing temperatures, particularly during the breeding season when individuals are highly site faithful. This information can help identify areas where populations might be particularly exposed to climate extremes due to a lack of refugia and where habitat management measures should take place.