DOI: 10.5061/dryad.brv15dv80
title: Metabolic rates and growth data for: Do small precocial birds enter torpor to conserve energy during development?

description: Precocial birds hatch feathered and mobile, but when they become fully
 endothermic soon after hatching, their heat loss is high and they may
 become energy-depleted. These chicks could benefit from using
 energy-conserving torpor, which is characterised by controlled reductions
 of metabolism and body temperature (Tb). We investigated at what age the
 precocial king quail Cortunix chinensis can defend a high Tb under a mild
 thermal challenge  and whether they can express torpor soon after
 achieving endothermy to overcome energetic and thermal challenges.
 Measurements of surface temperature (Ts) using an infrared thermometer
 showed that king quail chicks are partially endothermic at 2-10 days, but
 can defend high Tb at a body mass of ~13 g. Two chicks expressed shallow
 nocturnal torpor at 14 and 17 days for 4 to 5 hours with a reduction of
 metabolism by &gt; 40% and another approached torpor threshold.
 Although chicks were able to rewarm endogenously from the first torpor
 bout, metabolism and Ts decreased again by the end of the night, but they
 rewarmed passively when removed from the chamber. The total metabolic rate
 increased with body mass. All chicks measured showed a greater reduction
 of nocturnal metabolism than previously reported in quails. Our data show
 that shallow torpor can be expressed during the early postnatal phase of
 quails, when thermoregulatory efficiency is still developing, but heat
 loss is high. We suggest that torpor may be a common strategy for
 overcoming challenging conditions during the development in small
 precocial and not only altricial birds.
description: Oxygen consumption
 measurements using open-flow respirometry. Two animals were measured
 concurrently and were placed individually into 500 ml metabolic chambers
 in a temperature-controlled cabinet.  Dried outside air was pumped through
 these chambers at a rate of approximately 300 ml
 min<sup>-1</sup>. By employing two-way solenoid valves,
 reference outside air and the air from the metabolic chambers was measured
 sequentially every 9 minutes, 3 min for each channel. Air exiting the
 chambers was again dried and flow rate was measured with a mass flow meter
 (Omega FMA-5606); the oxygen content in a 100 ml
 min<sup>-1</sup> subsample was then determined with an
 O<sub>2</sub> analyser (FOX Field oxygen analysis system
 Version 1.01, Sable System, FXO301-01R). Outputs from the flow meter and
 the thermocouples from each respirometry chamber were digitized via a 14
 bit A/D converter (Data Taker DT100), whereas the
 O<sub>2</sub> analyser was interfaced with the PC directly via
 a serial port. Temperature control within the climatic chamber, channel
 switching, calculations and data storage were performed with a custom
 program written by G. Körtner in Visual Basic 6 (Microsoft Inc.). Oxygen
 consumption was calculated based on flow rate and the
 O<sub>2</sub> differential between reference and chamber air
 using Eqn. 3a from Withers (1977) assuming a RQ of 0.85. This RQ would
 result in a maximum error of 3% if the RQ was actually 0.7 or 1 (Withers,
 1977). Prior to measurements, the span of the
 O<sub>2</sub> analyser was set against outside air and the
 mass flow meter were calibrated with a custom-made bubble meter (Levy
 1964). <b>Withers P.C.</b> (1977). Measurement of VO2, VCO2, and evaporative water loss with a flow-through mask. <i>Journal of Applied Physiology.</i> <b>42</b>, 120-123 <b>Levy A</b>. (1964). The accuracy of the bubble meter method for gas flow measurements. <i>Journal of Scientific Instruments</i>. <b>41</b>, 449