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Predation pressures on sooty terns by cats, rats and common mynas on Ascension Island in the South Atlantic
Island and Ocean Ecosystems, BRB
Available Online

Dickey, R.C.

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Hughes, B.J.

,

Reynolds, S.J.

2019
Despite the presence of invasive black rats (Rattus rattus), common mynas (Acridotheres tristis), and feral domestic cats (Felis catus), sooty terns (Onychoprion fuscatus) breed in large numbers on Ascension Island in the tropical South Atlantic Ocean. These introduced predators impact the terns by destroying eggs or interrupting incubation (mynas), eating eggs (mynas and rats), eating chicks (rats and cats), or eating adults (cats). Between 1990 and 2015, 26 censuses of sooty terns and five of mynas were completed and myna predation was monitored on 10 occasions. Rat relative abundance indices were determined through trapping around the tern colonies and rat predation was monitored by counting chick carcasses. Cat predation was quantified by recording freshly killed terns. Prior to their eradication in 2003, cats had the greatest impact on sooty terns and were depredating 5,800 adults and 3,600 near-fledging chicks (equivalent to the loss of 71,000 eggs) each breeding season. We estimated that 26,000 sooty tern eggs (13% of all those laid) were depredated by approximately 1,000 mynas. Rats were not known to depredate sooty terns prior to cat eradication but in 2005, 131 of 596 ringed (monitored) chicks (22%) were depredated by rats. In 2009 chick carcass density was 0.16 per m2. Predation by rats hugely increased in the absence of cats and was the equivalent of 69,000 eggs. Care is needed when applying our findings to seabirds globally. The scarcity of alternative food sources and seasonally high density of easily available prey in the sooty tern colony may have magnified predation by cats, rats and mynas.
Eradication and control programmes for invasive mynas (Acridotheres spp.) and bulbuls (Pycnonotus spp.): defining best practice in managing invasive bird populations on oceanic islands
Island and Ocean Ecosystems, BRB
Available Online

Reynolds, S.J.

,

Saavedra Cruz, S.

2019
Invasive plants and animals inflict much damage on native species and this is particularly the case on isolated oceanic islands with high degrees of endemism. Such islands commonly are important refugia for species of high conservation value. Some of the most pervasive and potent of invasive animal species are birds of the myna (Acridotheres) and bulbul (Pycnonotus) genera that historically were introduced to isolated islands as biological control agents for the management of insect pest species that can cause considerable economic damage to agricultural crops and wider ecosystems. In this paper we consider a number of ‘successful’ eradication and control programmes targeting mynas and bulbuls. We review the locations and taxa where 17 such programmes took place and report that the common myna (Acridotheres tristis) has been the most heavily targeted species in eradication eff orts followed by the red-whiskered bulbul (Pycnonotus jocosus). Common mynas were also at the focus of control programmes as were jungle mynas (Acridotheres fuscus) and red-vented bulbuls (Pycnonotus cafer). By far the most favoured method of eradication and control was trapping whereas mist-netting was employed rarely. We discuss ‘best practice’ in planning and executing such eradication and control programmes on oceanic islands so as to maximise their benefits to local human communities. We outline measures that must be adopted pre-, during and post-intervention in both programme types. They include adequate resourcing, local engagement and the integration of both traditional ecological knowledge and established conservation theory.