Avian Extinction and Mammalian Introductions on Oceanic Islands

Blackburn, Tim M.; Cassey, Phillip; Duncan, Richard P.; Evans, Karl L.; Gaston, Kevin J.

doi:10.1126/science.1101617

Cited by 735 publications

(692 citation statements)

References 14 publications

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“…Non-migratory and island birds have been suggested to have particularly high extinction risk [39,40]. For island birds (defined here as species with at least 90% of their range on oceanic geological origin or distant continental/ island states), we find these assertions confirmed at the global scale, as they are disproportionately more threatened than expected (17% of island birds versus 8% of mainland birds are threatened; x 2 1 ¼ 109.7, p , 0.01; table 1).…”

Section: Resultsmentioning

confidence: 99%

Unravelling the structure of species extinction risk for predictive conservation science

2010

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Extinction risk varies across species and space owing to the combined and interactive effects of ecology/life history and geography. For predictive conservation science to be effective, large datasets and integrative models that quantify the relative importance of potential factors and separate rapidly changing from relatively static threat drivers are urgently required. Here, we integrate and map in space the relative and joint effects of key correlates of The International Union for Conservation of Nature-assessed extinction risk for 8700 living birds. Extinction risk varies significantly with species' broad-scale environmental niche, geographical range size, and life-history and ecological traits such as body size, developmental mode, primary diet and foraging height. Even at this broad scale, simple quantifications of past human encroachment across species' ranges emerge as key in predicting extinction risk, supporting the use of land-cover change projections for estimating future threat in an integrative setting. A final joint model explains much of the interspecific variation in extinction risk and provides a remarkably strong prediction of its observed global geography. Our approach unravels the species-level structure underlying geographical gradients in extinction risk and offers a means of disentangling static from changing components of current and future threat. This reconciliation of intrinsic and extrinsic, and of past and future extinction risk factors may offer a critical step towards a more continuous, forward-looking assessment of species' threat status based on geographically explicit environmental change projections, potentially advancing global predictive conservation science.

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Section: Resultsmentioning

confidence: 99%

Unravelling the structure of species extinction risk for predictive conservation science

2010

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“…The loss of anti-predator behaviour in evolutionary time can have important contemporary consequences [23], such as promoting the extinction of prey that have become naive due to the loss of anti-predator behaviour [47]. Because mice do not respond to fox cues on a nearby island that does not contain foxes, but does contain owl predators [29], relaxed selection resulting from loss of fox predators over evolutionary timescales can lead to the lack of a response to fox predators in island mice.…”

Section: Discussionmentioning

confidence: 99%

An island-wide predator manipulation reveals immediate and long-lasting matching of risk by prey

Orrock

Fletcher

2014

Proc. R. Soc. B.

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Anti-predator behaviour affects prey population dynamics, mediates cascading effects in food webs and influences the likelihood of rapid extinctions. Predator manipulations in natural settings provide a rare opportunity to understand how prey anti-predator behaviour is affected by large-scale changes in predators. Here, we couple a long-term, island-wide manipulation of an important rodent predator, the island fox (Urocyon littoralis), with nearly 6 years of measurements on foraging by deer mice (Peromyscus maniculatus) to provide unequivocal evidence that prey closely match their foraging behaviour to the number of fox predators present on the island. Peromyscus maniculatus foraging among exposed and sheltered microhabitats (a measure of aversion to predation risk) closely tracked fox density, but the nature of this effect depended upon nightly environmental conditions known to affect rodent susceptibility to predators. These effects could not be explained by changes in density of deer mice over time. Our work reveals that prey in natural settings are cognizant of the dynamic nature of their predators over timescales that span many years, and that predator removals spanning many generations of prey do not result in a loss of anti-predator behaviour.

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“…A filter effect occurs when islands that suffered more extinctions of species had fewer remaining rare species that would be listed as being under threat. Past studies have suggested that the numbers of introduced mammalian predators result in a filter effect on the number or proportion of threatened species (Blackburn et al 2004, Trevino et al 2007. Our results revealed the influences of anthropogenic activities on the number of threatened bird species on islands, through direct and indirect influences of human population size on past extinctions and the introduction of mammalian predators.…”

Section: Discussionsupporting

confidence: 55%

“…We began with a large published data set of the richness (i.e., number of species) of avifaunas of 220 oceanic islands (data supplemental to Blackburn et al 2004, original data from Biber 2002), augmented with additional information for 18 (for extinctions) and 21 (for threatened species) of the islands (Trevino et al 2007. Information in the dataset included the area of the islands (viz., island size), distance to a continental mainland, species richness of the original (pre-human colonization) avifaunas, number of humanintroduced mammalian predators, years since historical human colonization of the islands, number of extinctions since historical colonization, and number of currently threatened species (updated from BirdLife International 2012).…”

Section: Methodsmentioning

confidence: 99%

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Supplemental Information 1: Human Impacts Data

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Extinctions and threats of extinctions in avifaunas on oceanic islands appear to be influenced by several island characteristics and introduced mammalian predators. These predators may have caused a "filter effect"; low numbers of threatened avian species on some islands might be due to high rates of past extinctions. Using path analysis, we examined these factors and the influence of human population size (as an indicator of human activity) on the number of species extinctions and threatened bird species on islands. Human population size had substantial influences on the number of extinctions Abstract. Extinctions and threats of extinctions in avifaunas on oceanic islands appear to be influenced by several island characteristics and introduced mammalian predators. These predators may have caused a "filter effect"; low numbers of threatened avian species on some islands might be due to high rates of past extinctions. Using path analysis, we examined these factors and the influence of human population size (as an indicator of human activity) on the number of species extinctions and threatened bird species on islands. Human population size had substantial influences on the number of extinctions (standardized partial regression coefficient ρ = 0.315, N = 172, P = 0.0005) but not on the number of threatened species on oceanic islands (ρ = -0.061, P = 0.43), independent of the number of introductions of predator species. The number of extinctions on islands produced a significant filter effect (viz., had a negative impact; ρ = -0.186, P = 0.003) on the number of currently threatened species. The activities of human populations, including mammalian predators they introduced, have likely resulted in a greater number of bird extinctions on these islands, and producing a significant filter effect, wherein islands with larger human populations now have fewer threatened species.

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Avian Extinction and Mammalian Introductions on Oceanic Islands

Cited by 735 publications

References 14 publications

Unravelling the structure of species extinction risk for predictive conservation science

Unravelling the structure of species extinction risk for predictive conservation science

An island-wide predator manipulation reveals immediate and long-lasting matching of risk by prey

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