The removal of rodents from Yabu island allows survival of benefit species

Study Extent

The study had taken place on the island in year 2020 monitoring rat absence and presence and also observation of benefit species.

Sampling

Rat Trapping 60 Snap traps baited with roasted coconut were deployed across the island following the established transect lines from the eradication operation. See the locations of the rat snap traps in relation to the original rat bait stations from the 2018 rat eradication operation in Appendix 1. The rat snap trap monitoring was conducted over 3 consecutive nights (17th – 19th February). The snap trap status in each station throughout all the transect lines was recorded at (6-8am the next morning). Bird Population Count The bird population count was conducted from 4pm to 6pm on 20th February 2020. The bird counts were carried out from a distance, in a boat, using binoculars and with the naked eye. The count started from the southern part of the island (camp site) around the western part of the island, the northern then the eastern side of the island. The number of roosting seabirds and nests along the coastline was recorded. Bird counts were conducted by two observers in which one concentrated on counting the Red footed boobies while the other observer counted the Brown boobies and the Lesser frigate birds. Land Bird Assessment Spot lighting is a search method used, at night, to find and catch birds using headlamps and torches to illuminate the sky to attract bird’s attention. This was conducted to monitor other ground nesting or burrowing seabirds that can potentially breed on the island. Yabu Island will likely attract ground nesting birds such as the collared petrel now that the rats have been removed. Spotlighting was conducted over 2 nights (19-20 February, 2020) at 2 different sites. The first night of spotlighting was conducted at a high elevation spot on the eastern side of the island and the second night conducted on the western side of the island, but along the beach. See Appendix 1 for the locations of the spot lighting sites. The bird species encountered during the 2 nights of spotlighting was recorded. Opportunistic Observation All general observations by each team member was recorded.

Method steps

1. Rat Trapping 60 Snap traps baited with roasted coconut were deployed across the island following the established transect lines from the eradication operation. See the locations of the rat snap traps in relation to the original rat bait stations from the 2018 rat eradication operation in Appendix 1. The rat snap trap monitoring was conducted over 3 consecutive nights (17th – 19th February). The snap trap status in each station throughout all the transect lines was recorded at (6-8am the next morning). Bird Population Count The bird population count was conducted from 4pm to 6pm on 20th February 2020. The bird counts were carried out from a distance, in a boat, using binoculars and with the naked eye. The count started from the southern part of the island (camp site) around the western part of the island, the northern then the eastern side of the island. The number of roosting seabirds and nests along the coastline was recorded. Bird counts were conducted by two observers in which one concentrated on counting the Red footed boobies while the other observer counted the Brown boobies and the Lesser frigate birds. Land Bird Assessment Spot lighting is a search method used, at night, to find and catch birds using headlamps and torches to illuminate the sky to attract bird’s attention. This was conducted to monitor other ground nesting or burrowing seabirds that can potentially breed on the island. Yabu Island will likely attract ground nesting birds such as the collared petrel now that the rats have been removed. Spotlighting was conducted over 2 nights (19-20 February, 2020) at 2 different sites. The first night of spotlighting was conducted at a high elevation spot on the eastern side of the island and the second night conducted on the western side of the island, but along the beach. See Appendix 1 for the locations of the spot lighting sites. The bird species encountered during the 2 nights of spotlighting was recorded. Opportunistic Observation All general observations by each team member was recorded.

Yabu, also called by local people ‘Bird Island’ is a 7 ha, uninhabited island in Kadavu Province, Fiji (18° 50’ 40’’ S, 178° 30’ 08’’ E) (Figure 1). It is located 3.5 km from Buliya Island (home of the landowners); 63 km from Vunisia, Kadavu Island; and 25 km from Suva, Fiji’s capital. Yabu is only accessed by sea. On the south side, Yabu Island rises steeply from a narrow plateau, adjacent to the main beach, to a ridge that reaches 50 m at its highest point. The island is bound by cliffs on its west and north sides. Most of the cliffs are covered with vegetation all the way to the rocks at the bottom. There are a couple of cliff areas that are devoid of vegetation halfway to the bottom. There is a sparsely vegetated rock stack off the northern tip of the island. In addition to the main beach on the south side, there are two smaller ones on the east side. On this side the island slopes down from the ridge to the beaches.