Cotoneaster and Mejiro

The Cotoneaster (Cotoneaster pannosus) is an attractive shrub that was introduced to the Hawaiian Islands from China as an ornamental plant. Even though it is recognized as an invasive species around the world, it is still available at many garden stores as a landscape plant. It’s important for everyone to research the invasive status of a plant before putting it in the ground.

The cotoneaster is very adaptable, and able to grow in a wide range of climates and soil types. It does especially well in cool wet mountain climates. It forms dense thickets there, that crowd out native species. It has abundant pink flowers that develop into bright red berries. The plentiful red berries are poisonous to humans, but can be eaten by birds—which distribute the seeds into the forests.

The Japanese white-eye bird, or mejiro (Zosterops japonicus), is the most abundant land bird in the Hawaiian Islands. It was introduced in 1929 by the Hawai‘i Board of Commissioners of Agriculture and Forestry (BCAF), to control insects that were damaging agricultural crops.

Around the same time, the Hawaiian lowlands had been deforested. Native birds were no longer heard where people lived. Private clubs, like the Honolulu Mejiro Club and Hui Manu Society, introduced song birds from around the world to repopulate the lower elevations of islands. The mejiro was one of the many introduced birds.

At first, the mejiro seemed to be a beneficial addition to Hawai‘i. It’s an attractive bird that people enjoy seeing and hearing. It does a good job of controlling insects, and it replaces extinct birds to pollinate and spreads seeds of native plants.

On the other hand, it has become too successful. It is common on all islands, and has moved into the native forests. It’s competing with native birds for food, and spreads seeds from invasive plants like the cotoneaster.