Invertebrate Abundance Study

By November 23, 2016Nature

North Island’s Environment team has recently set up a long-term invertebrate study, with the aim of assessing the Island’s food availability for the potential re-introduction of the Seychelles Magpie Robin. Measuring habitat quality is an important component of endangered species management as it often determines whether individuals settle and breed successfully in a particular area. This endemic species is classified as Critically Endangered on the IUCN Red List of Threatened Species and can currently only be found on five islands in the Seychelles. We hope that through this study we can make that number a six.

The invertebrate abundance project is coordinated by the Green Islands Foundation who has also involved other islands that currently host a population of the Seychelles Magpie Robin, so that we may compare our findings and determine if North Island is a suitable candidate for their re-introduction. Assessing the abundance and diversity of invertebrates in the upper soil surface and litter is the most important indicator of territory quality for the ground-feeding Seychelles Magpie Robin.

Aride, Cousin, Denis and Frégate are conducting the same survey. The methodology used is the same as Njoroge (2002) used on Cousin, Aride and Curieuse, who based his method on sampling done by Komdeur (1996) on Frégate Island. Following the same method will allow the comparison of data over time and between the different islands.

The study involves quantifying the number of invertebrates in soil samples in different habitats on the Island and makes use of 25x25m randomly-chosen sampling plots. A modified insect pitfall is placed in each plot, which is collected once per month and re-placed at a new location in the sampling plot. Afterwards the collected sample is sorted and the found invertebrates are identified. A new microscope has been purchased so that our environmentalists can inspect the invertebrates in detail.

Through this study, we aim to gather evidence to support the future translocation of this endangered endemic bird to North Island and secure its survival in the long term. The project has been running for seven months on North Island and we can expect the results of the study towards the end of next year. The invertebrate study forms part of our conservation efforts and feeds into our Noah’s Ark rehabilitation programme where we aim to turn back the hands of time and restore North Island back to its original pristine state.

Evidence of the success of this programme has been the fact that other bird species such as the Seychelles Blue Pigeon and breeding populations of Wedge-tailed Shearwaters and White-tailed Tropicbirds have returned to North Island of their own accord. The Seychelles White-eye was successfully re-introduced in 2007 and the population on North Island has flourished. Please look out for next month’s Seychelles White-eye update from the latest census results.