Branta Issues > Issue №8 (2005)

Fishing commensalism of gulls in relation to Great Crested Grebe (Podiceps cristatus) and Goosander (Mergus merganser).

A. M. Arkhipov

The note describes a mid-winter observation. Yellow-legged Gull and Black-headed Gull were preying on fish when Great Crested Grebe and Goosander chased a victim beneath the water surface. The observation took place on Kuchurganskiy Liman situated in Odessa region, Ukraine.

The grebe or goosander dived on depth and apparently pursued a fish stock. When they dipped, gulls being close to them took off and watched them flying at height up to 2-3 m over water. When the pursuer came to the surface the gull was keeping itself in the hovering flight over water for a few time and then plunged into the water to catch fish frighten upwards by an under-water fisher. Sometimes gulls managed to capture prey, and a grebe or goosander emerged and ate the caught fish without obstacle. No competition was between under-water catchers and spongers.