Metabolic power of European starlingsSturnus vulgarisduring flight in a wind tunnel, estimated from heat transfer modelling, doubly labelled water and mask respirometry

Abstract

SUMMARY It is technically demanding to measure the energetic cost of animal flight. Each of the previously available techniques has some disadvantage as well advantages. We compared measurements of the energetic cost of flight in a wind tunnel by four European starlings Sturnus vulgaris made using three independent techniques: heat transfer modelling, doubly labelled water (DLW)and mask respirometry. We based our heat transfer model on thermal images of the surface temperature of the birds and air flow past the body and wings calculated from wing beat kinematics. Metabolic power was not sensitive to uncertainty in the value of efficiency when estimated from heat transfer modelling. A change in the assumed value of whole animal efficiency from 0.19 to 0.07 (the range of estimates in previous studies) only altered metabolic power predicted from heat transfer modelling by 13%. The same change in the assumed value of efficiency would cause a 2.7-fold change in metabolic power if it were predicted from mechanical power. Metabolic power did not differ significantly between measurements made using the three techniques when we assumed an efficiency in the range 0.11–0.19, although the DLW results appeared to form a U-shaped power-speed curve while the heat transfer model and respirometry results increased linearly with speed. This is the first time that techniques for determining metabolic power have been compared using data from the same birds flying under the same conditions. Our data provide reassurance that all the techniques produce similar results and suggest that heat transfer modelling may be a useful method for estimating metabolic rate.

Why marathon migrants get away with high metabolic ceilings: towards an ecology of physiological restraint

“…Experimental measurements of the cost of bird flight carried out in wind tunnels over many hours (Pennycuick et al, 1997;Kvist et al, 2001;Ward et al, 2004;Engel et al, 2006;SchmidtWellenburg et al, 2006;Schmidt-Wellenburg et al, 2008) also vary widely, but gravitate toward values around 9 times BMR (Videler, 2005). Migrating shorebirds have the capacity to process food and store fuel at fast rates (Kvist and Lindström, 2003) related to them usually being in a hurry and because they make such long-distance flights.…”

Biomechanics of bird flight

“…For many years, it appeared that the curve for P met was flat at intermediate flight speeds, which suggested that efficiency is lowest in the range of preferred flight speeds (reviewed in Ellington, 1991). Recently, efforts to measure P met using a variety of techniques including doublelabelled water, heat transfer and gas respirometry, reveal that the curve for P met is U-shaped much as that for P mus and P aero , with muscular efficiency in the range of 20% Ward et al, 2004;Engel et al, 2006;Bundle et al, 2007) (Fig.·2C). Comparison of the curves for P met and P mus in cockatiels Nymphicus hollandicus, measured in two different studies, suggests that efficiency is not constant across speeds and that V mp and V mr are both faster when measured using P met compared with P mus Bundle et al, 2007) (Fig.·2).…”

“…The first level is metabolic power input (P met ) to the muscles, directly of interest to a flying, foraging bird, and generally a realm of study for respiratory, thermal and chemical physiologists. P met is the rate the bird expends chemical energy to supply the flight muscles, and it may be measured using double-labeled water (Nudds and Bryant, 2000;Ward et al, 2004;Engel et al, 2006), labeled bicarbonate (Hambly et al, 2002), oxygen consumption and carbon dioxide production Ward et al, 2004;Bundle et al, 2007). P met equals the sum of mechanical power output from the muscles (P mus ) and the rate of heat loss from the muscles.…”

“…P met equals the sum of mechanical power output from the muscles (P mus ) and the rate of heat loss from the muscles. Thus, P met may also be modeled using measures of heat transfer (Ward et al, 2004).…”

Flight metabolism in relation to speed in Chiroptera: Testing the U-shape paradigm in the short-tailed fruit batCarollia perspicillata

“…Measurement technique may also play a key role in defining flight power-velocity relationships. For example, Ward et al (Ward et al, 2004) assessed flight power by respirometry, doubly labeled water and heat transfer modeling in a single bird species (Sturnus vulgaris) and found a U-shaped relationship when they employed the doubly labeled water method, but a linear increase when using the other measurement techniques.…”