An Introduced Bird Competitor Tips the Balance Against Hawaiian Species

ScienceDaily (May 23, 2012) — Biologists Leonard Freed and Rebecca Cann from the University of Hawaii at Manoa have been studying birds at Hakalau Forest National Wildlife Refuge for 20 years. Located on an old cattle ranch on the windward slope of Mauna Kea on the Island of Hawaii, it was established in 1985 to protect 8 species of rare and endangered perching birds. The refuge and its volunteers planted over 400,000 seedlings of native koa trees in an abandoned pasture to restore high elevation forest.

The once-rare white-eye colonized the restoration area, grew rapidly in it, but then surged into the old-growth forest below. Freed and Cann estimated that tens of thousands of native birds were lost.

Their study was recently published in the open access journal NeoBiota.

The researchers had previously shown competition between white-eyes and native birds on their study sites. With increased numbers of white-eyes, young of all native species measured had stunted growth, indicating that food was becoming a problem. They also documented that birds of all ages had difficulty replacing their feathers. Each problem, both unprecedented in nature, occurred at the same time. In contrast to the forest adjacent to the restoration area, native birds deeper within the forest had normal growth and feather replacement where white-eyes were still rare.

Read more:  http://www.sciencedaily.com/releases/2012/05/120523135529.htm