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Data from: Controlling trapping, overgrazing and invasive vegetation is key to saving Java's last population of the Black-winged Myna

Citation

Squires, Thomas M et al. (2022), Data from: Controlling trapping, overgrazing and invasive vegetation is key to saving Java's last population of the Black-winged Myna, Dryad, Dataset, https://doi.org/10.5061/dryad.8gtht76r3

Abstract

The Black-winged Myna (Acridotheres melanopterus) is an Endangered passerine endemic to the islands of Java and Bali, Indonesia. Illegal trapping to supply the cage-bird trade has led to its near-total extinction, with the global population estimated to number fewer than 100 individuals. The only known population of Black-winged Mynas on Java occurs at Baluran National Park (BNP). These data were generated to meet the two primary aims of the linked paper: the first was to estimate the Black-winged Myna (Acridotheres melanopterus) population size and range at BNP; and the second was to use species distribution modelling to evaluate the potential suitability of areas currently unoccupied by Black-winged Mynas across BNP to identify priorities for management intervention. We carried out line-transect distance sampling following the standard distance analysis method to estimate the population size. A total of 56 detections of groups of Black-winged Mynas were recorded along line transects and are included in the dataset. These records are associated with the land cover type for that segment of the transect, the perpendicular distance of the record to the transect, and the survey effort associated with each transect. To produce the species distribution model, we used three predictor raster layers along with all Black-winged Myna presences recorded (not freely available, see below) and a generated set of pseudo-absences. The dataset contains both the raw data used to create the land cover classification as well as the final raster. The raw data used to produce the habitat classification contains classified points (n = 426) from across BNP, which were used as a training and test data for a random forest land cover classification.

Methods

Supervised land cover classification

We have provided the raw data used as the input for a supervised land cover classification. During fieldwork, the observer visited points around the national park and classified them into one of eight broad land cover types (open savanna, savanna woodland, dry deciduous woodland/shrubland, dry deciduous forest, thorny acacia scrub, teak plantation, tropical evergreen forest, beach forest, and mangrove forest). This gave 221 classified points. To increase the sample size of the classes with fewest classified points, there are an additional 205 points that were classified using Google Earth image interpretation. For a detailed description of the land cover types adopted here, please see Supplementary Material Table S1. The data are recorded in the UTM zone 50S coordinate system.

Distance analysis

The raw data used to produce the population size estimate are provided. However, all location data have been removed. These data were collected using the standard line transect distance sampling method. A detailed description of the method used is provided in the Methods section of the associated paper. Birds seen in flight were not recorded, but those seen taking off or landing were recorded to that position. For detections where group size was unknown, we used the average group size for all known groups. During post-processing, transects were split into segments based on land cover type, which was taken from our supervised land cover classification. Sampling effort was then calculated for each transect segment. We included a 'habitat openness' covariate for analysis, for which open savanna and woodland savanna were considered 'open habitat' and woodland land cover types were considered 'closed habitat'. The headings in the table provided follow those required by package Distance in R. The units used for Effort are kilometres and area is measured in km2. The 'distance' is the perpendicular distance of the detection from the transect and is measured in metres.

Habitat suitability analysis

Due to the sensitivity of our study species, the coordinates for Black-winged Myna presences cannot be provided here. Bona fide researchers are welcomed to contact the corresponding author to request these data, which can be used with the three predictor layers provided to replicate the species distribution modelling procedure and determine potentially suitable habitat for the myna. The NDVI layer was calculated from the Landsat 8 image covering Baluran from 8 October 2018 (downloaded from https://earthexplorer.usgs.gov); the land cover classification layer was generated using our habitat data and we also developed a habitat openness layer from it, for which each pixel represents the proportion of open (open savanna or woodland savanna) vs. closed (all other woodland types) habitat pixels in the 0.56 km2 (25 × 25) surrounding the target pixel.

Usage Notes

The location of Black-winged Myna presences have not been included in the dataset because the species is Endangered and threatened by illegal trapping. Requests to access these data should be made to the corresponding author (tom.squires@stu.mmu.ac.uk).

Funding

Chester Zoo

Manchester Metropolitan University

Oriental Bird Club