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Gliding flight in a jackdaw: a wind tunnel study.

M Rosén¹, A Hedenström

¹Department of Animal Ecology, Lund University, Ecology Building, SE-223 62 Lund, Sweden. mikael.rosen@zooekol.lu.se

The Journal of Experimental Biology

|February 27, 2001

Summary

This study reveals how jackdaws adjust their wingspan and tail to optimize gliding flight. Birds achieve maximum lift-to-drag ratio and minimum sinking speed by altering their wing configuration at different airspeeds.

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Area of Science:

Biomechanics and Aerodynamics
Avian Flight Dynamics

Background:

Understanding bird flight mechanics is crucial for bio-inspired engineering and ecological studies.
Previous models for predicting bird flight performance often lack empirical validation across diverse species.

Purpose of the Study:

To investigate the gliding flight performance of the jackdaw (Corvus monedula) in a controlled wind tunnel environment.
To analyze how jackdaws modify their wingspan, wing area, and tail configuration to optimize glide efficiency across various speeds.
To develop a more accurate predictive model for avian gliding flight based on empirical data.

Main Methods:

Wind tunnel experiments were conducted on a jackdaw to measure gliding performance parameters.
Measurements included airspeed, sinking speed, wingspan, wing area, and tail configuration.
Analysis involved calculating glide super-polars, lift-to-drag ratios, and Reynolds numbers; re-analysis of existing data from other bird species was also performed.

Main Results:

Jackdaws achieved steady gliding between 6 and 11 m/s, with minimum sinking speed at 7.4 m/s and best glide speed at 8.3 m/s.
The maximum lift-to-drag ratio (L:D) was 12.6 at 8.5 m/s, with wingspan decreasing linearly with speed.
Tail configuration varied with speed, being spread at lower speeds and fully furled above 9 m/s; a new equation for predicting wingspan and wing area was derived.

Conclusions:

Jackdaws exhibit dynamic adjustments in morphology (wingspan and tail) to optimize gliding efficiency.
Existing theoretical models for span ratio optimization do not accurately predict observed bird flight configurations.
The derived alternative equations provide a more accurate method for calculating sinking rates in gliding birds, applicable to various flight models.

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