Wind gradient exploitation during foraging flights by black skimmers (Rynchops niger)

Area of Science:

• Avian flight dynamics
• Bioenergetics
• Animal behavior

Background:

• Birds utilize environmental features like wind gradients to minimize flight costs.
• Black skimmers (Rynchops niger) exhibit unique foraging behavior (skimming) involving flight above water with their lower mandible submerged.
• Previous research on black skimmers focused on ground effect, neglecting aerial interactions.

Purpose of the Study:

• To investigate the hypothesized "halfpipe skimming" strategy in black skimmers.
• To determine if black skimmers exploit wind gradients for energy conservation during foraging.
• To quantify the potential cost reduction from this aerial maneuver.

Main Methods:

• Filming black skimmer flight paths using video recordings.
• Measuring wind speed and direction at two coastal field sites.
• Analyzing 70 bird tracks to correlate flight patterns with wind gradients.

Main Results:

• Skimmers flew upwind during ascent and downwind during descent, consistent with energy harvesting from wind gradients.
• Observed flight patterns suggest a deliberate wind gradient energy extraction maneuver.
• The wind gradient and skimmer behavior indicate a potential foraging cost reduction of up to 2.5%.

Conclusions:

• Black skimmers employ a "halfpipe skimming" strategy to exploit wind gradients.
• This strategy may significantly reduce the energetic costs of their specialized foraging flight.
• Understanding these aerial interactions provides new insights into avian flight efficiency.