Particle image velocimetry (PIV) permits measurement of airflow in the near-field and wake of birds as they fly.  We use a dual-pulsed Nd-YAG laser to illuminate

a flow field that is seeded with micron-sized particles of olive oil vapor.  Cross-correlation of image pairs provides air velocity and derivatives such as vorticity..  We use velocity and vorticity to calculate lift and drag on the body, wings and tail.