Vegetative Impacts of Nesting Cormorants

Tree nesting cormorants will eventually kill the host tree through the deposit of their guano. This process of killing trees prematurely is a naturally occurring process found throughout the natural world. Beavers kill trees by damming creeks and flooding forest areas. Natural wildfires also kill trees. These trees eventually become "snags" providing habitat for a different array of wildlife such as woodpeckers and den dwelling mammals. The creation of snags is a vital process to forest renewal. All photos below taken at East Sister Island (see East Sister Island briefing notes for further information). Click on photos to enlarge.

Double-crested cormorants typically nest in dense colonies in trees

Even though cormorant colonies can reach densities of hundreds and thousands of
nesting birds, they are concentrated in very small areas.

Tree nesting birds will strip foilage and twigs from trees for nesting building materials.

Guano deposits will eventually kill both the tree and ground vegetation, and is part if the vital process of natural succession.