Indirect Effects of Introduced Predators on Seabird Islands

Russell, James C.

doi:10.1093/acprof:osobl/9780199735693.003.0009

Cited by 22 publications

(19 citation statements)

References 70 publications

(94 reference statements)

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“…Such multiple operations are becoming increasingly feasible (Russell, 2011), and may have the additional advantage of reducing the chance of such effects as competitor or mesopredator release (Courchamp, Langlais & Sugihara, 1999;Caut et al, 2007;Dilley et al, 2016). The possibility of such outcomes should be evaluated on a caseby-case basis (see Helmstedt et al, 2016), ideally with eradication planning considering responses in a whole-ecosystem context (Zavaleta, Hobbs & Mooney, 2001).…”

Section: Discussionmentioning

confidence: 99%

Seabird population changes following mammal eradications on islands

Brooke

Bonnaud

Dilley

et al. 2017

Animal Conservation

101

133

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Seabirds are among the most threatened groups of birds, and predation by invasive mammals is one of the most acute threats at their island breeding stations. Island restoration projects increasingly involve the eradication of invasive non-native mammals, with benefits for seabirds and other island fauna. To date, demonstrated benefits of invasive mammal eradication include increased seabird nesting success and enhanced adult survival. However, the recovery dynamics of seabird populations have not been documented. Drawing on data from across the world, we assemble population growth rates (k) of 181 seabird populations of 69 species following successful eradication projects. After successful eradication, the median growth rate was 1.119 and populations with positive growth (k > 1; n = 151) greatly outnumbered those in decline (k < 1; n = 23, and seven showed no population change). Population growth was faster (1) at newly established colonies compared to those already established, (2) in the first few years after eradication, (3) among gulls and terns compared to other seabird groups, and (4) when several invasive mammals were eradicated together in the course of the restoration project. The first two points suggest immigration is important for colony growth, the third point reflects the relative lack of philopatry among gulls and terns while the fourth reinforces current best practise, the removal of all invasive mammals where feasible.

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Section: Discussionmentioning

confidence: 99%

Seabird population changes following mammal eradications on islands

Brooke

Bonnaud

Dilley

et al. 2017

Animal Conservation

101

133

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“…However, alternative factors seem to limit the density of owls to a very small number (less than 15 pairs). The density of owls is so low that they do not have a severe (indirect) effect on seabirds, in contrast to the Farallon Islands where mice subsidize burrowing owls preying upon ashy storm-petrels (Russell, 2011). Because rats and owls prey on the same seabird life-stages (eggs and chicks), the direct effect of abundant rats (up to 80 rats ha À1 ) greatly outweighs any negative effect of owl predation.…”

Section: Interactions With Apex Predators: Mesopredator or Hyperpredamentioning

confidence: 99%

Trophic roles of black rats and seabird impacts on tropical islands: Mesopredator release or hyperpredation?

Ringler

Russell

Corre

2015

Biological Conservation

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Corre. Trophic roles of black rats and seabird impacts on tropical islands: Mesopredator release or hyperpredation?. Biological Conservation, Elsevier, 2015Elsevier, , 185, pp.75-84. 10.1016Elsevier, /j.biocon.2014 a b s t r a c tRats contribute to the decline of tropical seabird populations by affecting their breeding success through direct predation of eggs and chicks. When they coexist with other predators, invasive rats may also generate indirect interactions via the changes they impose on the structure of communities and trophic interactions following invasion ('hyperpredation process'), or when apex predators are eradicated from the ecosystem ('mesopredator release effect'). Understanding these effects is necessary to implement restoration operations that actually benefit threatened seabird populations. We investigated these processes on two French tropical seabird islands of the western Indian Ocean, Europa and Juan de Nova, where black rats coexist with two different apex predator species (introduced cats and potentially native barn owls). The parallel use of several methods (diet analysis, stable isotopes, seabird monitoring) to identify trophic roles of rats revealed that the direct impact of rats on seabirds was particularly high on Europa where only rats and owls occur, with high consumption of chicks resulting in low breeding success for several seabird species. We also suggested that hyperpredation associated with top-down regulation of cats is occurring on Juan de Nova, although territoriality of cats may buffer this process. Conversely we found evidence that mesopredator release effect is unlikely, irrespective of the apex predator identity. Considering the most likely effects on both islands we provided recommendations on eradication priorities to mitigate the risk of local extinction that seabirds are currently facing.

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“…For extremely long‐lived, low‐fecundity species such as those in the order Procellariiformes, which includes the storm petrels, shearwaters, and albatrosses, adult survival is the key demographic parameter in determining population growth or decline (Nur and Sydeman ). Management actions to counter threats to seabird survival can be difficult to implement, but elimination of introduced species impacting seabird colonies has proved successful (Russell , Jones et al. ).…”

Section: Introductionmentioning

confidence: 99%

Evaluating population impacts of predation by owls on storm petrels in relation to proposed island mouse eradication

et al. 2019

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We quantify the expected demographic benefit to a seabird of conservation concern, the ashy storm‐petrel Oceanodroma homochroa, from the proposed eradication of introduced house mice Mus musculus on the South Farallon Islands, California. A key objective of the eradication is to reduce storm petrel predation by burrowing owls Athene cunicularia, which stopover on the island during their fall migration. Mouse trapping and field surveys of both owls and depredated storm petrel carcasses conducted during 2000–2012 reveal a strongly seasonal, inter‐related pattern among the three species: When owls arrive during the fall, mice are super‐abundant and the overwhelming choice of prey for those owls that remain. In the winter, the mouse population crashes just as storm petrels begin to arrive in large numbers; owls that remain on the island switch to preying upon storm petrels until May, when they depart to breed. Capture–recapture analyses of storm petrels showed (1) annual adult survival was inversely related to owl abundance, especially during January–April, and (2) storm petrels demonstrated a declining trend in abundance 2006–2012. The latter was associated with low rates of adult survival, high abundance of overwintering burrowing owls, and high incidence of depredated storm petrels. To evaluate projected impacts to storm petrels of a change in owl predation, we developed a Leslie matrix model, incorporating environmental stochasticity. We modeled future storm petrel population trajectories, allowing for different levels of owl‐mediated predation. Our results suggest that a reduction in owl abundance, a projected consequence of the elimination of mice, has the potential to substantially reduce overall storm petrel mortality, thereby reducing storm petrel declines and increasing the likelihood of stable trends in the future. While long‐term benefits to storm petrels of mouse eradication are apparent, the risk of increased predation due to prey‐switching by owls also needs to be addressed. This study highlights uncertainty of outcomes, which must be considered in evaluating management impacts. This study demonstrates the value of concurrent, continuous, long‐term datasets in providing a quantitative basis for management to aid the conservation of species of concern.

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Indirect Effects of Introduced Predators on Seabird Islands

Cited by 22 publications

References 70 publications

Seabird population changes following mammal eradications on islands

Seabird population changes following mammal eradications on islands

Trophic roles of black rats and seabird impacts on tropical islands: Mesopredator release or hyperpredation?

Evaluating population impacts of predation by owls on storm petrels in relation to proposed island mouse eradication

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