Estrategias de alimentación del Cormorán Grande (Phalacrocorax carbo sinensis) en el río Ebro (N España)

Abstract

Foraging strategies of the Cormorant (Phalacrocorax carbo sinensis) in the Ebro River (N Spain)
During four consecutive winters (1991-95) individual and social foraging bouts of cormorants were studied in the main feeding areas of the Ebro River (Navarra, N Spain). Cormorant utilized two foraging strategies during winter in the river: in groups or alone. The mean group size was of 78.7 I 53.3 individuals. The main prey were: the French nase (Chondrostoma toxostoma) in number and the Barbel (Barbus graellsii) in biomass, with great monthly variation. Social fishing allowed shorter dives, higher feeding success and larger prey than solitary foraging.