Assessing the consistency of hawkbill nest selection between local nesting habitats in The Thousand Islands of Jakarta: implication for conservation practices
Mohamad Isnin Noer (a*), Yusuf Adhie Prakoso (b), Agung Sedayu (a)

a) Biology Study Program, Universitas Negeri Jakarta
*mohamadisnin[at]unj.ac.id
b) Graduate Student of Biology Study Program, Universitas Negeri Jakarta

Abstract

The Thousand Island consists of a group of low-lying islands off the coast of Jakarta that experience different degrees of natural and anthropogenic pressures, resulting in variations in local environmental conditions. Nest selection of hawkbill turtles in this group of the island has not been conducted broadly, studies are only available from one or two islands. This is challenging for practitioners to address conservation practices on nest selection in other islands only based on data compiled from only a small subset of islands. This study aimed to determine the environmental characteristics of the nests selected by hawksbill turtles for nesting at a population level and identify whether there are differences in nest characteristic selection between sub-populations/islands. We used the coefficient of variation to statistically assess the preferences of hawkbill turtles on particular nests in a broad range of habitat variations by comparing environmental values on nest sites and random vacant sites. Coefficient of variation was also used to compare the preferences of hawkbill turtles in selecting a nest on two islands (Peteloran Timur dan Kayu Angin Bira). At the population level, the findings show that some nest characteristics have values which less varied than the values of the environment (nest and vacant sites combined) which indicates that hawksbill turtles exhibit non-random nest selection, but Mann-Whitney tests showed statistically no differences among groups suggesting that hawkbills turtles in Ten Thousand Islands choose their nests randomly. A comparison of the characteristics of the nests on the two islands shows that there are differences in several variables, namely the beach width, the distance to the highest water line, and canopy cover. Hawkbill turtles in Peteloran Timur tend to select nests in areas within reach of the coastline and subtidal, but prefer sites with shady vegetation cover.

Keywords: Hawkbill turtle- Thousand Islands- coeficient of variation- Jakarta

Topic: Biology