Strategies for land-bird conservation on Mauritius

The native wildlife of Mauritius is highly threatened by a variety of influences other than habitat destruction. Protection from habitat destruction atone cannot guarantee its conservation and the damage already sustained is not fully reversible Therefore, the ideal for conservation-maintenance or restoration of self-sustaining populations of all species in native ecosystems-is presently unattainable. We assessed three long-term strategies for maintaining and increasing populations of threatened native birds on the mainland and offshore islets of Mauritius, with respect to efficacy, sustainability, and side-effects. Rehabilitation of native vegetation on the mainland is likely to improve food availability over limited areas, but it can only form the basis of a long-term bird conservation strategy when population density of introduced animals, especially predators, can he reduced sustainably, at low financial cost, and without adversely affecting native wildlife. Marooning bird populations on ecologically rehabilitated islets can eliminate the predator problem, but they would be vulnerable to catastrophes (especially cyclones) and possibly disease and much habitat manage ment work is still needed. A third novel strategy-enhancement of mainland habitat using exotic plants-allows creation of source habitats, greatly reducing the predator threat. It also permits larger areas to be managed and at lower cost, than is the case with intensive rehabilitation. Habitat management regimes for conservation of threatened species or communities must be designed specifically to alleviate population-limiting factors. Ln altered environments certain exotic plants can be essential to the survival of native animal species. The most effective conservation measure must not be assumed always to be the rehabilitation of native vegetation.