As a child in Saaz, Nachtigall was fascinated by the shiny objects that often appeared in formation flight on the sky, not knowing about their deadly load (Nachtigall 1987). Curious about flight, he went on to spend most of his scientific carrier investigating the dynamics and energetics of animal flight, where flexible appendages and body parts provide lift and propulsion. For his investigations, he applied and built instruments for kinematic recordings, scales to measure fluid dynamic forces, as well as cages, basins, flow channels, and tunnels to provide controlled conditions for the study of flight and swimming. Nachtigall used comparative morphological and biophysical studies to establish basic principles. He became a highly productive scientific author (Zupanc et al. 2024). Here are selected highlights of some of his research.

In his doctoral thesis, he built a stroboscope combined with a commercial 16 mm camera to track markers attached to the appendages of diving beetles (Coleoptera, Dytiscidae) and a spring scale to measure body drag (Nachtigall 1960). Later, supported by the German Science Foundation, he constructed a 16 mm high speed camera enabling 800 frames/s which, in combination with a strobe light, enabled a stroboscobic micrograph within each high-speed frame. His observations stressed the efficiency of the leg morphology used in swimming. As a closing statement, Nachtigall (1961) writes: “It is the best-known thrust apparatus in the animal kingdom making use of the resistance principle”. Measurements on models of the beetle’s body in a water tunnel, a wind tunnel, and a towing tank yielded information on drag optimization and stability of the dytiscid body (Nachtigall and Bilo 1965). He employed these developed techniques to illuminate the kinematics and locomotion patterns of the larvae of different flies (Dipterae) and diving beetles (Dytiscidae).

A major advancement in the investigation of flight was the use of the tethered fly. A fly was fixed on a mechanical 3D-scale to control flight in front of a wind tunnel, allowing unpreceded recordings of wing movements at different wind speeds, thus significantly enhancing our understanding of insect flight (Nachtigall 1966). Later these findings were complemented by the consideration of unsteady effects (Nachtigall 1979a). In his investigation on the flight dynamics of honey bees, Nachtigall and his coworker Hanauer-Thieser could show that body and legs contribute considerably to lift (Nachtigall and Hanauer-Thieser 1992). Again, newly designed pieces of equipment, such as a round-about, a closed ring-chamber for insect flight, and a closed wind-tunnel with a low volume, allowed detailed investigations of the energetics of bee flight (Rothe and Nachtigall 1989; Nachtigall et al. 1995). During his visit to Wilson’s laboratory, Nachtigall investigated how different muscles contribute to the control of the wing kinematics (Nachtigall and Wilson 1967; Nachtigall 1968a). Later, this line of research was pursued by his team member Bernhard Möhl.

In parallel, Nachtigall’s established methodical advances were adapted and enhanced to illuminate the mechanics and energetics of bird flight. Early studies focused on aerodynamic profiles during gliding flight (Nachtigall and Wieser 1966). Nachtigall (1998b) details a comprehensive summary of further developments and new experimental stations, such as large-scale wind tunnels in the laboratories in Saarbrücken equipped with instruments for stereo-photogrammetry, and respiratory measurements. Among others, these studies delivered information about thermoregulation and water homeostasis in pigeons (Biesel and Nachtigall 1987). Long-distance flight seemed not to be limited by fuel but by the fact that evaporative water loss exceeded metabolic water production. The cybernetics of bird flight became a main subject of his early and long-lasting team member Dietrich Bilo.

Nachtigall’s expertise helped to interpret the function of the lobed fins of the coelacanth (Fricke et al. 1987). To further advance our understanding of fish locomotion, he designed a facility that included tanks and flow tunnels to investigate the biophysics of undulatory swimming in fish (Blickhan et al. 1992; Kesel et al. 1989). These studies notably characterized the efficiency of undulatory propulsion based on kinematics and the flow in the wake, as well as muscle recruitment.

Within the special research field of the German Science Foundation “Constructions in Nature” (SFB 230 Natürliche Konstruktionen) funded from 1984 to 1995, participants worked to achieve a general understanding of natural and technical constructions. As an expert in biomechanics and bionics, Nachtigall made significant contributions to this research program. His projects included research on the mechanical stability of grass in the wind tunnel (Nachtigall et al. 1986). His interest on biological light weight structures is also indicated by investigations of the mechanical properties of insect wings (e.g. Kesel et al. 1998).

Always with an eye on science, Nachtigall was also a naturalist. To go for a walk with him meant to be confronted step-by-step with the Latin names for almost everything seen. In numerous small projects, he documented behaviors in the wild of flight in seeds, insects, and birds. Using his private equipment, he evaluated the data and published the results in a series of twenty-one articles for the interested entomologist (e.g., Nachtigall 2018).