Bird Ecology and Conservation A Handbook of Techniques

Which of the alternative fuel substrates are catabolized can be determined from

concentrations of blood plasma metabolites. Free fatty acids and glycerol are prod-

ucts of fat metabolism from adipose tissue, while uric acid is the end product from

protein catabolism and hence indicates the use of protein, such as the consumption

of flight muscle mass. Triglycerids and VLDLs indicate the formation of adipose

tissue (fat accumulation). For an example see Jenni-Eiermann et al. (2002).

7.4.3Endocrinology

Many behavioral and physiological processes during migration are proximally

under hormonal control (see Chapter 9 for suitable techniques).

7.5 Flight in wind tunnels

Birds can be tracked in the field using the different methods described above.

However, for experiments under controlled conditions, a wind tunnel is

required. A wind tunnel creates a smooth (laminar) airflow in a test section where

birds are trained to fly (Figure 7.5). There are a few wind tunnels dedicated for

bird flight research in Europe and North America, but especially two new wind

tunnels of recirculating design at Lund University, Sweden and the Max Planck

Institute, Seewiesen, Germany, give very low turbulence in air flow (Figure 7.5;

Pennycuick et al. 1997). This is important in order to generate a natural situation

reflecting flight through nonturbulent air. If one is interested of studying the

Flight in wind tunnels| 171

Fig. 7.5The Lund University wind tunnel for bird flight research.

Test section

Bellmouth

Fan

Contraction Settling section Wide-angle

diffuser

Large

corners

Tilting

mechanism

The wind tunnel can be tilted Main diffuser Cooler

Glass fibre Steel Air flow

First

diffuser

THE LUND WIND TUNNEL

Small

corners