Recent decline of the St Helena Wirebird Charadrius sanctaehelenae

McCulloch

Remedios

et al. 2013

Ibis

Self Cite

Sex-related variation in survival is common in birds and, as it influences effective population size and population growth, is important for conservation and species management. Here we assessed incubation behaviour and sex-related survival in a threatened sexually monomorphic shorebird, the St Helena Plover Charadrius sanctaehelenae. Males incubated at night, the period of highest activity of cats, which are likely to be predators of breeding birds. In spite of behavioural differences between the sexes, adult survival was not significantly different between males and females, suggesting that sex-biased behaviour need not lead to sex-related survival, and thus behavioural differences may not impact upon the adult sex ratio.

Section: Methodsmentioning

confidence: 99%

“…). Although direct evidence is scarce for other life stages, it is likely the same species prey upon chicks and that cats are the main predator of adults (McCulloch ). As cats are mostly active at night, we conjectured that this may lead to reduced survival of the sex that incubates at night.…”

mentioning

confidence: 99%

Sex differences in incubation behaviour but not mortality risk in a threatened shorebird

McCulloch

Remedios

et al. 2013

Ibis

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“…500 individuals), probably as a consequence of lower grazing intensity in pastures and subsequent vegetation growth. Recent conservation management for the species has focused on increasing stocking levels and removing alien vegetation from suitable pasture breeding sites (McCulloch ). Habitat management alone, however, may not be sufficient to increase population growth rate of ground‐nesting waders (Burns et al .…”

Section: Introductionmentioning

confidence: 99%

Habitat‐specific effectiveness of feral cat control for the conservation of an endemic ground‐nesting bird species

Oppel

Journal of Applied Ecology

Vickery

et al. 2014

Summary1. Invasive non-native species are one of the greatest drivers of the loss of biodiversity world-wide. Consequently, removing or controlling invasive predators should generally benefit vulnerable native species. However, especially on islands, where most mammalian predators are introduced, these predators may also prey on other invasive mammals. Removing only apex predators may lead to increases of meso-predators that may in turn increase predation pressure on native wildlife. 2. We examined the benefits of a feral cat Felis catus control programme on nest survival of a critically endangered ground-nesting bird, the St Helena Plover Charadrius sanctaehelenae in two habitat types, harbouring c. 30% of the global population of this species. We monitored nest success and the activity of introduced mammals (cats, rabbits Oryctolagus cuniculus, rats Rattus rattus and Rattus norvegicus, and mice Mus musculus) over 2 years, before and after controlling feral cats. 3. Live trapping removed 56 feral cats from our study areas. In the semi-desert, rabbit and mouse activity increased, but rat activity remained low after feral cat control. In pastures, rat and mouse activity increased after feral cat control, while rabbit activity remained constant. 4. Nest survival of plovers increased more than threefold in the semi-desert, but increased only marginally in pastures. This difference may be due to an increase in rat activity and potentially rat predation following cat control in pastures, whereas no increase in rat activity was observed in the semi-desert. 5. Synthesis and applications. Our study shows habitat-specific consequences of feral cat control on ground-nesting bird productivity after 1 year, probably mediated by differences in the availability of alternative prey. The results highlight the importance of experimental trials and a thorough understanding of the interactions between multiple invasive species before predator-control operations are implemented over larger scales. On islands with multiple invasive species, there may not be a simple generic approach to predator management (other than removing all invasive species simultaneously).

“…Its population size has stabilized recently (mean population 2008–2012 = 369 ± 33.9 sd individuals; Saint Helena National Trust unpubl. data) after declining by more than 40% between 2000 and 2005 (McCulloch ). Scrub encroachment and other habitat changes are likely to have played a large part in this decline but increased predation pressure may also have been involved (McCulloch , Burns ).…”

mentioning

confidence: 99%

“…data) after declining by more than 40% between 2000 and 2005 (McCulloch ). Scrub encroachment and other habitat changes are likely to have played a large part in this decline but increased predation pressure may also have been involved (McCulloch , Burns ). As on other isolated oceanic islands, many species have been introduced to St Helena since its discovery by humans in 1502 (Ashmole & Ashmole ).…”

mentioning

confidence: 99%

No overall benefit of predator exclosure cages for the endangered St. Helena Plover Charadrius sanctaehelenae

McCulloch

Székely

et al. 2013

Ibis

Self Cite

Predator exclosure cages are designed to increase the clutch survival of ground‐nesting birds. Predator exclosures provided for the endangered St. Helena Plover Charadrius sanctaehelenae, however, did not result in differences in clutch survival between protected and control nests and may have resulted in elevated adult mortality. Exclosures did not exclude all cats, the dominant nest predator, and it is likely that cats caused the adult mortalities observed close to the exclosures. A population model indicates that even if predator exclosures had excluded all cats, the benefits of increased clutch survival would have been more than negated by the estimated decrease in adult survival. The overall effect of predator exclosures needs to be clarified for other species, taking into consideration annual productivity and adult survival, to understand the circumstances in which predator exclosures are beneficial.