The concept of ring wing aircraft, with circular closed wings, promised revolutionary benefits like enhanced lift, fuel efficiency, and shorter runway requirements. Once explored by innovators like ...

On the closed wings the secondaries show obvious pale fringes on the brown-headed. Finally, the brown-headed has a longer and more pointed wing, and the outermost primary (P9) is equal in length ...

Older immatures not distinguishable from adults; small percentage retain a few juvenal wing coverts or other feathers. Flight: quick, flicking wingbeats followed by short, closed-wing glides.