How Do Rats Affect Seabirds?

In a study, researchers examined how introduced rats affect seabird colonies. They found that their impact on seabirds varied depending on the species and region, and was not the sole cause of the decline in seabird populations. In addition, other factors like food availability and habitat loss can limit seabird colonies.

Rats may affect seabirds by reducing the abundance of food available to seabirds. For example, seabirds are important distributors of nutrients in many island ecosystems, particularly in coral reefs. When seabirds feed in the open ocean, they leave nitrogen-rich guano, which is leached into the sea and nourishes algae, sponges, corals, and other aquatic plants.

In the Western Indian Ocean, rats have encroached upon islands that are a vital breeding ground for tropical seabirds. Rats are present on nearly 93% of island groups in this region, where seabird populations are most vulnerable to rat invasion. Unfortunately, few studies have documented the impact of rats on seabirds.

The Isles of Scilly Recovery Project (ISRP) commissioned a feasibility study to investigate the effects of rats on the islands. The study was conducted by Wildlife Management International Limited, and was largely supported by the entire island community.