Search the SPREP Catalogue

The Baja California Pacifc Islands, Mexico, are globally important breeding sites for 22 seabird species and subspecies. In the past, several populations were extirpated or reduced due to invasive mammals, human disturbance, and contaminants. Over the past two decades, we have removed invasive predators and, for the last decade, we have been implementing a Seabird Restoration Programme on eight groups of islands: Coronado, Todos Santos, San Martín, San Jerónimo, San Benito, Natividad, San Roque, and Asunción. This programme includes monitoring; social attraction techniques; removal of invasive vegetation; reducing human disturbance; and an environmental learning and biosecurity programme. Here, we summarise historical extirpations and recolonisations during the last two decades of restoration actions, and we update the status of breeding species after more than a decade. To date, from 27 historically extirpated populations, 80% have returned since the ?rst eradication in 1995. Social attraction techniques were key in recolonisations of Cassin’s auklet (Ptychoramphus aleuticus), royal tern (Thalasseus maximus), and elegant tern (T. elegans). A total of 19 species breed on these islands, four more species than a decade ago, including 12 new records. The most abundant seabirds, black-vented shearwater (Puffnus opisthomelas), Cassin’s auklet, western gull (Larus occidentalis), and Brandt’s cormorant (Phalacrocorax penicillatus), have shown a remarkable population increase. Current threats include the potential reintroduction of invasive mammals, guano mining, recreational activities, pollution, and commercial ?sheries. To maintain these conservation gains in the long-term it is necessary to continue implementing restoration actions and reinforcing protection on these important natural protected areas.

Invasive alien species are one of the primary threats to native biodiversity on islands worldwide, and their expansion continues due to global trade and travel. Preventing the arrival and establishment of highly successful invasive species through rigorous biosecurity is known to be more economic than the removal of these species once they have established. However, many islands around the world lack biosecurity regulations or practical measures and establishing biosecurity will require social and financial investments. Guiding these investments towards islands where native biodiversity is at highest risk from potential invasions is of strategic importance to maximise conservation benefit with limited resources. Here we implement an established prioritisation approach, previously used to identify which islands will have the greatest conservation gains from the eradication of invasive species, to identify which islands would benefit the most from establishing or improving biosecurity. We demonstrate this approach for 318 islands in the Caribbean UK Overseas Territories and Bermuda where we considered all threatened native terrestrial vertebrates that are vulnerable to the most harmful invasive vertebrates (black and brown rats, cats, small Indian mongoose, green iguana). The approach calculates the increase in conservation threat score resulting from anticipated negative effects of potential invaders on native biodiversity, and highlighted Sombrero (Anguilla) and Cayman Brac (Cayman Islands) as important islands where threatened reptile species would likely be eliminated if rats, feral cats or mongoose invaded. Feasibility and cost implications should now be investigated more closely on the highlighted islands. The prioritisation presented here can be expanded to more islands and more invasive/native taxa (herbivores, plants and invertebrates), but requires a classification of the severity of potential impacts between invasive and native species for which currently little information exists. Besides highlighting opportunities for biosecurity, this approach also highlights where knowledge gaps about population sizes of and threats to reptiles with restricted ranges exist.

Socorro Island is part of the Revillagigedo National Park, Mexico. At 132 km2, it is the Mexican island with the highest level of endemism. It provides habitat for 117 vascular plant species, 26% of which are endemic. There is also an endemic blue lizard (Urosaurus auriculatus) and eight endemic terrestrial birds. Socorro’s ecosystem had been heavily degraded by invasive mammals for the past 140 years. Feral sheep (Ovis aries) destroyed one third of the island’s habitat and feral cats (Felis catus) severely impacted the island’s avifauna and the Socorro blue lizard. Together, feral sheep and cats are responsible for the extinction in the wild of the Socorro dove (Zenaida graysoni) and the Socorro elf owl (Micrathene whitneyi graysoni) and have been a serious threat to other vulnerable species, particularly Townsend’s shearwater (Pu?nus auricularis). As such, the island’s restoration is a high priority. We conducted a feral sheep eradication from 2009 to 2012, using aerial and terrestrial methods, aided by Judas sheep and trained dogs, to kill 1,762 animals. The vegetation recovery has been remarkable, as well as the improvement of soil properties such as compaction, nitrogen, organic carbon, phosphorus, and calcium. In 2011, we initiated a feral cat control programme, which soon became an eradication project. The ongoing feral cat eradication has been a challenge, due to Socorro’s large size, vegetation and topographical complexity. By December 2016, 502 cats had been dispatched, using soft leg-hold traps equipped with telemetry transmitters and lethal traps: a total e? ort of 50,000 trap-nights. Cat abundance has decreased very signi?cantly and catch per unit of e? ort indicates that the eradication is nearing completion. The abundance of the Socorro blue lizard and terrestrial birds has already increased. We estimate completing the feral cat eradication by the end of 2017, when we will shift to a veri?cation of eradication phase.

The Orkney Islands, o? the north-east coast of Scotland, support highly significant?cant cultural and natural heritage. The combined land area of the 70 islands is 990 km2 (380 sq mi),

A successful ground-based eradication of black rats (Rattus rattus) was undertaken on the remote, uninhabited Shiant Isles of north-west Scotland over winter (14 October–28 March) 2015–16. The rat eradication was carried out as part of the Shiants Seabird Recovery Project, which aims to secure long-term breeding habitat for protected seabirds and to attract European storm petrels and Manx shearwaters to nest on the Shiants. Throughout the eradication operation, teams were stationed on two of the three main Shiant islands (Eilean an Tighe, Eilean Mhuire), with access to the third (Garbh Eilean) via a boulder causeway from Eilean an Tighe. Bait (Contrac® blocks containing the anticoagulant bromadiolone 0.005% w/w), was deployed in a grid of 1,183 bait stations covering all areas of the islands and sea stacks. Bait stations were set 50 m apart, with intervals reduced to 25 m in coastal areas of predicted high rat density. Difficult areas were accessed by boat and cliff s of ~120 m in height were accessed by abseiling down ropes made safe using either bolted anchors or ground stakes. The team of staff and volunteers worked through difficult conditions, deploying bait and monitoring intensively for any surviving rats using a combination of tools. The islands were declared rat free in March 2018. This ambitious and challenging project has greatly enhanced UK capacity in rodent eradications for the purposes of conservation.

Invasive rodents are present on approximately 80% of the world’s islands and constitute one of the most serious threats to island biodiversity and ecosystem functioning. The eradication of rodents is central to island conservation eff orts and the aerial broadcast of rodenticide bait is the preferred dispersal method. To improve the efficiency of rodent eradication campaigns, the generation of accurate and real-time bait density maps is required. Creating maps to estimate the spatial dispersion of bait on the ground has been carried out using traditional GIS methodologies, which are based on limiting assumptions and are time intensive. To improve accuracy and expedite the evaluation of aerial operations, we developed an algorithm for the numerical estimation of rodenticide density (NERD). The NERD algorithm performs calculations with increased accuracy, displaying results almost in real-time. NERD describes the relationship between bait density, the mass fl ow rate of rodenticide through the bait bucket, and helicopter speed and produces maps of bait density on the ground. NERD also facilitates the planning of helicopter fl ight paths and allows for the instant identification of areas with low or high bait density. During the recent and successful rodent eradication campaign on Banco Chinchorro in Mexico, carried out during 2015, NERD results were used to enable dynamic decision-making in the fi eld and to ensure the efficient use of resources.