Dataset "Seasonal variation in thermoregulatory capacity of three closely related Afrotropical Estrildid finches introduced to Europe"
A species' potential geographical range is largely determined by how physiologically the species reacts to its changing environment. It is therefore crucial to study the physiological mechanisms that species use to maintain their homeothermy in order to address biodiversity conservation challenges, such as the success of invasions of introduced species. The common waxbill Estrilda astrild, the orange-cheeked waxbill E. melpoda and the black-rumped waxbill E. troglodytes are small Afrotropical passerines that have established invasive populations in regions where the climate is colder than in their native ranges. As a result, they are excellent model species for studying potential mechanisms for coping with a colder and more variable climate. The "cold tolerance hypothesis" and the "climate variability hypothesis" were tested in captive-bred waxbills for explaining seasonal variation in thermoregulatory traits, such as basal (BMR), summit (Msum) metabolic rates and thermal conductance. We found that, from summer to autumn, their ability to resist colder temperatures increased. This was not related to larger body masses or higher BMR and Msum, as predicted by the cold tolerance hypothesis. Instead, species downregulated BMR and Msum toward the colder season, suggesting energy conservation mechanisms to increase winter survival. In line with the climate variability hypothesis, BMR and Msum were most strongly correlated with temperature variation. Moreover, common waxbill and black-rumped waxbill, whose native ranges encompass the highest degree of seasonality, showed the most flexibility in metabolic rates. This ability to adjust thermoregulatory traits, combined with increased cold tolerance and energy saving mechanisms, may facilitate their establishment in areas characterized by colder winters and less predictable weather.