Olive white-eye recovery programme

The Mauritius olive white-eye (OWE) is part of an ancient Indian Ocean white-eye lineage with birds colonising from Asia prior to the subsequent evolution of the African species. It is currently the rarest of the nine remaining endemic land bird species of Mauritius with less than 150 pairs in the Black River Gorges National Park. This incredibly low population size is due to extensive habitat loss and the impact of invasive mammal species, particularly rats (Rattus rattus and R. norvegicus).

Mauritius olive white-eye sat on a branch
Adult Mauritius olive white-eye

Prior to 2001 very little was known about the species biology, range and population size. However, through intensive research and monitoring a better understanding of its ecological requirements and population limiting factors has been established.  This knowledge has been used to inform the reintroduction of the OWE to the predator-free island nature reserve, Ile aux Aigrettes. Currently, this population, of around 60 individuals, is intensively monitored and managed through the provision of supplementary feed.

Find out more: Mauritius olive white-eye recovery programme 

Why we are there

ZSL’s Institute of Zoology (IoZ) is closely involved in the OWE project and, along with our conservation partners, provides scientific evidence underpinning the species recovery programme. The recovery programme is implemented by the Mauritian Wildlife Foundation and the National parks and Conservation Service (Government of Mauritius), with support from the Durrell Wildlife & Conservation Trust (DWCT) and Chester Zoo.

To date research conducted at IoZ has shown how rats significantly reduce breeding success in OWEs and hence contribute to the ongoing population decline. Research has also shown and that this can be mitigated for by the control of this invasive species and that a long-term solution to maintaining OWE populations on mainland Mauritius is the development of predator-free ‘mainland islands’. This is a first for Mauritius and currently feasibility trials are underway. Our research has also assessed the effectiveness of the provision of supplementary feed as a conservation management tool for OWEs and this may be refined in the long -term through targeted habitat management. 

This work not only benefits the Mauritius olive white-eye but also the other endemic passerine species of Mauritius and projects globally, facing similar threats of invasive species and long-term management uncertainty by combining science, conservation and communication. 


  • A viable OWE population in the long-term.
  • A suite of relevant, refined conservation management actions focused on:
    • the provision of supplementary feed;
    • habitat restoration; 
    • and the management of invasive rat species.  
  • The development of international collaboration to drive evidence-based species conservation

Project information

Key Species

Mauritius olive white-eye or oiseau lunette (Zosterops chloronothos) 

The Mauritius olive white-eye is an endemic passerine listed as Critically Endangered on the IUCN (International Union for Conservation of Nature) Redlist and is in the top 10% of the EDGE (Evolutionary Distinct and Geographically Endangered) bird species list (Birdlife International 2016, Jetz et al 2014).

Other Material

PhD Thesis: The ecology and conservation of the Critically Endangered  Mauritius Olive white-eye

People Involved

Dr Malcolm Nicoll 
Prof Ken Norris
Dr John Ewen

Partners & Sponsors

Partners: Mauritian Wildlife Foundation, National Parks & Conservation Services (Government of Mauritius), Chester Zoo, Durrell Wildlife Conservation Trust

Sponsors: Chester Zoo