Meeting Abstract

41.6  Sunday, Jan. 5 11:30  Aquatic burst locomotion by hydroplaning and running in Common Eiders (Somateria mollissima) GOUGH, W.T.*; FARINA, S.C.; FISH, F.E.; Cornell University; Cornell University; West Chester University wgough0788@gmail.com

Eiders have high wing loadings that are near the accepted threshold for flightlessness in birds that can cause flight to be energetically expensive. Surface swimming by paddling generates waves that can limit maximum speed. These coastal sea-ducks can overcome the speed limitations of self-generated waves, known as hull speed, by performing rapid behaviors that generate dynamic lift (hydroplaning). We obtained high-speed videos (210 fps) of Common Eiders from a boat around the Isles of Shoals in the Gulf of Maine. A portable GPS unit was used to measure the speed as the boat paced the ducks. The videos showed two distinct hydroplaning behaviors: (1) “steaming”, which involved rapid paddling with the wings to propel the duck along the surface of the water and (2) “wing-assisted running,” during which the ducks lifted themselves completely out of the water and used their hind feet to paddle along the surface while flapping their wings. When steaming, the wings made substantial contact with the water in a rowing motion. During running, the wings were used for flight and only the feet made contact with the water, with a gait using alternating strokes of the hind limbs. The mean wingbeat frequency of steaming (4.57 ± 0.44 Hz) was slower than the wingbeat frequency of wing-assisted running (8.69 ± 0.65 Hz). The hull speed, which is based on the waterline length, was calculated to be 0.72 ± 0.05 m/s for Eiders. During steaming, ducks were found to exceed hull speed by 5.9 times. When burst locomotion by Eiders is necessary, hydroplaning and running are likely energetically economical and rapid alternatives to diving or flight for these heavy marine ducks.