Invasive species – plants, animals, or others – pose major problems for native species. Some of the worst cases of invasion come from Pacific islands where many birds that evolved without predators have become extinct or endangered due to introduced mammals. A recent study of bellbirds in New Zealand provides a counter example of birds changing their behavior to cope with an introduced predator.
The study focused on the New Zealand bellbird (Anthornis melanura), an endemic species that was exposed to introduced mammalian predators within the last 200 years. It compared nesting behavior at four types of nests:
- Mainland bellbird nests with introduced predators present
- Mainland bellbird nests with introduced predators removed
- Island bellbird nests with no introduced predators
- Tasmanian honeyeater nests with native predators
This study gives some hope that other native island birds can adapt relatively quickly to the presence of new predators. These particular adaptations are specifically suitable for woodland birds, whose nests can be easily hidden. Seabird colonies and flightless birds face greater challenges in protecting their nests from predators. The best policy is still to prevent the spread of harmful invasive species or remove them where possible.