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Data from: Thermoregulatory costs of the innate immune response are modulated by winter food availability in a small passerine


Watson, Hannah; Nilsson, Jan-Åke; Nilsson, Johan F. (2023), Data from: Thermoregulatory costs of the innate immune response are modulated by winter food availability in a small passerine, Dryad, Dataset,


1. In winter, a challenge to the immune system could pose a major energetic trade-off for small endotherms, whereby increasing body temperature (Tb; i.e. eliciting fever) may be beneficial to fight off invading pathogens yet incur a cost for vital energy-saving mechanisms.

2. Having previously shown that the availability and acquisition of energy, through manipulation of food predictability, influence the depth of rest-phase hypothermia in a wild bird in winter, we expected that the nocturnal thermoregulatory component of the acute-phase immune response would also be modulated by food availability.

3. By manipulating winter food availability in the wild for great tits, Parus major, we created an area offering a “predictable” and constant supply of food at feeding stations, while an unmanipulated area was subject to naturally “unpredictable” food. Birds were subject to an immune challenge shortly after dusk, and the thermoregulatory response was quantified via continuous recording of nocturnal Tb, using subcutaneous thermo-sensitive transponders.

4. In response to immune challenge, all birds increased Tb above the level maintained prior to immune challenge (i.e. baseline). However, birds experiencing a naturally unpredictable food supply elevated Tb more than birds with access to predictable food resources, during the period of expected peak response and for the duration of the night. Furthermore, “unpredictable-food” females took longer to return to baseline Tb. Assuming baseline nocturnal Tb reflects an individual’s optimum, based on their available energy budget, the metabolic cost of eliciting an acute-phase response for “unpredictable-food” birds was more than double that of “predictable-food” birds. The absence of differences in absolute Tb during the peak response could support the idea of an optimal Tb for immune system activation. Alternatively, “predictable-food” birds could have acquired tolerance to endotoxin as a result of using feeding stations, thus affording them reduced costs associated with a smaller Tb increase.

5. These findings shed new light on the trade-offs associated with food acquisition, thermoregulation and immune function in small-bodied endotherms. This knowledge is of increasing importance, given the predicted elevated pathogen risks associated with changes in climate and anthropogenic activities.


Body temperature data from roosting great tits (Parus major) was recorded using Biomark HDR Plus with standard racket antenna and thermo-sensitive passive integrated transponders (BioTherm 13, Biomark, US) located subcutaneously. Body temperature was measured every minute during the night, either following arousal, handling and immune challenge in birds subject to predictable or unpredictable food availability (Tb_food_manipulation.csv) or following only arousal and handling (Tb_control.csv). Body temperature data were processed to derive 10-minute and 60-minute rolling means. Ambient temperature data were collected using iButtons (DS 1922L, Maxim Integrated, US). For full methods, refer to the published article.


Vetenskapsrådet, Award: 2016-04240

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