DIVING ENERGETICS IN LESSER SCAUP (AYTHYTA AFFINIS, EYTON)

Area of Science:

• Animal Physiology
• Biomechanics
• Ecology

Background:

• Understanding the energetic costs of diving is crucial for avian ecology.
• Previous estimates of mechanical and aerobic energy expenditure in diving birds may not fully account for dynamic forces.

Purpose of the Study:

• To measure the mechanical and aerobic energy costs of voluntary feeding dives in lesser scaup (Aythya affinis).
• To identify the primary factors contributing to the energy expenditure during different phases of the dive.

Main Methods:

• Simultaneous measurement of mechanical and aerobic energy costs using closed-circuit respirometry.
• Observation of six lesser scaup during voluntary feeding dives to a depth of 1.5 m.

Main Results:

• Mechanical power output and aerobic power input were higher than previous estimates.
• Buoyancy was the dominant factor in mechanical costs, accounting for 62% of descent costs and 87% of feeding costs.
• Drag and inertial forces also contributed significantly to descent costs, while buoyancy loss due to air compression reduced overall buoyancy.

Conclusions:

• Energetic costs of diving are significantly influenced by buoyancy and dive-phase durations.
• Mechanical work and power output are substantially higher during descent compared to the feeding phase.
• Biomechanical models yield different estimates for descent versus feeding phases.