Prey of nesting Bald Eagles in northern California

Inland nesting Bald Eagles (Haliaeetus leucocephalus) in northern Californi a preyed on both native and introduced freshwater fish species, primarily b rown bullhead (Ameiurus nebulosus), Sacramento sucker (Catostomus occidenta lis), common carp (Cyprinus carpio) and tui chub (Gila bicolor). At most lo cations, eagles ate mainly fish; however, birds, principally American Coots (Fulica americana) and Mallards (Anas platyrhynchos),were more important t han fish at sites isolated from large rivers. Fish species taken by eagles varied between major drainages: Sacramento sucker were most common in eagle diets at impoundments along the Pit River and the American River, catfish predominated on the Feather River and Trinity River drainages, and tui chub were the principal prey of eagles nesting in the Lahontan System. Mean sta ndard lengths of common prey fishes ranged from 240 mm for brown bullhead t o 510 mm for carp; Sacramento sucker prey averaged 393 mm standard length. Productivity of eagle pairs using mostly native fishes on the Pit River was nearly identical to that of pairs taking mostly introduced fishes on the F eather River. We recommended that resource managers consider prey species c omposition and fish prey sizes in management decisions affecting Bald Eagle breeding habitat. Important manage ment factors affecting fish populations included dam construction and operation and nongame fish control.