How the abundance and diversity of insect populations in two areas of the Wellington region are affected by moisture, pH and depth of leaf litter, and what this could mean for the survival of the Petroica longipes (North Island Robin) population.

Franziska Plimmer
Candidate Number: 003740-0019
Word Count: 3824

Abstract
This research assignment looks at how the abundance and diversity of insect populations in the Wellington region are affected by moisture, pH and depth of leaf litter, and what this could mean for the survival of the Petroica longipes (North Island Robins) population.
Though initially the research was going to take place on Matiu Island, it was carried out in
Eastbourne and in Zealandia, a native wildlife sanctuary. Both these areas in Wellington were chosen because of their similarities to Matiu Island. In Eastbourne pitfall traps were placed in selected moist and dry areas for three weeks to determine levels of invertebrate abundance and diversity. In those same areas moisture, pH and depth of the leaf litter
(referred to as leaf litter quality) were measured by using a soil probe and a ruler. To link this back to the research question, ten minute observations of P. longipes and other birds were recorded at Zealandia in both a moist and dry area, as well as recording leaf litter quality measurements.
It is important to understand the factors that could affect the success of translocations.
From this study’s findings, a factor to consider could be how moisture affects invertebrate abundance. This is due to the findings showing that as leaf litter quality increased so did the
P. longipes’ food source (the ground-dwelling invertebrates). Findings also showed that there were more P. longipes found in moist areas than in dry areas, supporting the idea that lack of moisture could be a reason for the P. longipes’ low survival rates on Matiu Island.
Word Count: 259

Acknowledgements
I am very grateful to George Gibbs who helped the project get off the ground and who helped me design my pitfall traps. Thanks to Zealandia for permission to do research there. I owe special thanks to my project supervisor who answered so many of my questions and had to read this many times. And of course to my mother who helped me identify birds and insects at Zealandia.

Contents
Introduction ........................................................................................................................................ 1
Method of Investigation ..................................................................................................................... 2
Location........................................................................................................................................... 2
Maps................................................................................................................................................ 3
Pitfall traps in Eastbourne................................................................................................................... 5
Step by step method ....................................................................................................................... 7
Measuring leaf litter quality................................................................................................................ 9
Equipment ....................................................................................................................................... 9
Bird Observations in Zealandia ......................................................................................................... 10
Step-by-step method .................................................................................................................... 10
Raw Data ........................................................................................................................................... 11
Observations