Saddlebacks Philesturnus carunculatus have become extinct from much of their range in New Zealand due to predation by introduced mammals such as rats Rattus spp. This study investigates the success of reintroducing a population to an island in a lake.


Between 1989 and 1990, brown rats R. norvegicus were eradicated from Mokoia Island, Lake Rotorua, North Island, New Zealand. In April 1992, 36 saddlebacks were released on the island.

The number of birds on the island was then monitored from 1992 until 1997.



The population increased from the 36 birds released to 217 birds in September 1996. The population fell following the attempted eradication of mice but recovered to 200 by September 1997. Reproductive output declined over time as the population grew, and was best explained by density-dependence. The sex ratio was not significantly different from 50:50.

Note: If using or referring to this published study, please read and quote the original paper.


Output references

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence in synopses. Subjects covered so far include amphibians, birds, terrestrial mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read latest volume: Volume 17

Go to the CE Journal

Subscribe to our newsletter

Please add your details if you are interested in receiving updates from the Conservation Evidence team about new papers, synopses and opportunities.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust