DOI: 10.5061/dryad.73n5tb326
title: Data from: Thermoregulatory costs of the innate immune response are modulated by winter food availability in a small passerine

description: 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.
description: Body temperature data from roosting great tits (<em>Parus
 major</em>) 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.