The first objective was to assess the effects of thermal stress on key physiological mechanisms, including metabolism, mitochondrial function, oxidative stress, hormonal regulation, and cellular ageing markers such as telomere length. This objective has been partly achieved (75%). Data collection has been successfully completed for several physiological parameters, including body temperature and metabolic rate, which were measured in both nestlings and adult individuals using RFID-based temperature sensors and respirometry techniques. Blood samples were collected at multiple developmental stages, allowing longitudinal analyses of oxidative stress markers and molecular indicators. Laboratory analyses, including measurements of telomere length, mitochondrial DNA copy number, and heat shock protein expression, have been initiated and are currently ongoing. Preliminary observations suggest that individuals exposed to elevated temperatures exhibit increased metabolic activity and signs of accelerated telomere loss, although full analyses are still in progress.
The second objective was to evaluate the consequences of thermal stress on life-history traits such as growth, survival, and reproductive performance. This objective has also been partly achieved (75%). Growth trajectories were quantified through repeated measurements of body mass and structural size at different developmental stages. Fledging success and early survival were recorded across experimental treatments, and parental behaviour was monitored using an automated RFID system, enabling precise quantification of feeding rates and nest attendance. Initial results indicate that heat stress does not significantly affect growth rates, while parents may partially compensate through increased provisioning effort. However, long-term survival and reproductive consequences will require continued monitoring beyond the current reporting period.
The third objective was to determine whether responses to thermal stress vary along an urbanisation gradient. This objective has been fully achieved with respect to data collection. Field experiments were successfully implemented across multiple sites representing urban, peri-urban, and forest environments. Environmental variables, including temperature and humidity, were continuously recorded. Preliminary analyses suggest that individuals from urban environments may exhibit increased sensitivity to thermal stress, potentially reflecting them being at the margin of their acclimatisation processes.
The fourth objective was to disentangle genetic and environmental contributions to thermal stress responses using cross-fostering and common garden experiments. This objective has been partly achieved (20%). Cross-fostering was successfully implemented in the field to separate early environmental and genetic effects. However, the common garden experiment was not successful yet due to delays in the field. 2024 and 2025 were extremely bad years in terms of climatic conditions, and therefore for the bird. We had to delay the common garden experiment.
Altogether, the research has been published in two publications so far and 4 are under revision/preparation. The research has been presented in 5 conferences/invited seminars, 7 communication activities like school and public outreach events. During the project, the researcher has acquired advanced expertise in molecular biology techniques, including RT-qPCR for gene expression analyses, as well as in physiological measurements such as metabolic rate assessment and bioimpedance.
