Piscivorous birds are birds that eat fish (pisces =
fish, vorous = eating). These avian predators have an
affect on the survival of juvenile salmon and steelhead that
are migrating downstream past our dams. Avian predators found
along our reservoirs include mergansers, double-crested
cormorants, great blue herons, gulls, terns, loons, and grebes.
Chelan PUD conducts surveys along reservoirs to determine
distribution and abundance of avian predators. These
surveys help Chelan PUD manage bird habitat and behaviors in
order to reduce predation on juvenile salmonids passing through
our reservoirs and to minimize impacts on the birds.
Avian Predator Management
Piling caps have been installed on dock pilings at PUD-owned parks along Rocky Reach and Rock Island reservoirs. The piling caps prevent gulls and other birds from perching and using the pilings to prey on fish. Elimination of perch sites on pilings also forces gulls to use other areas at parks where they are more exposed to disturbances, making this portion of the river less attractive to gulls.
Grids of bird wires are installed over the tailraces (immediately downstream) of both Rock Island and Rocky Reach dams. The wires greatly discourage gulls and terns from flying in the tailrace of the dams to prey on fish. The wires force birds to utilize downstream areas for foraging. Fish are less susceptible to being preyed upon by birds in downstream areas were the river is calmer and the fish are able to swim at greater depths.
Hazing of the birds by using pyrotechnics (noise makers) such as propane cannons, bird screamers, and bangers also helps to keep piscivorous birds away from the tailraces of the dams where juvenile salmonids are most vulnerable to predation.