Summary1. Demographic models are assuming an important role in management decisions for endangered species. Elasticity analysis and scope for management analysis are two such applications. Elasticity analysis determines the vital rates that have the greatest impact on population growth. Scope for management analysis examines the effects that feasible management might have on vital rates and population growth. Both methods target management in an attempt to maximize population growth. 2. The Seychelles magpie robin Copsychus sechellarum is a critically endangered island endemic, the population of which underwent significant growth in the early 1990s following the implementation of a recovery programme. We examined how the formal use of elasticity and scope for management analyses might have shaped management in the recovery programme, and assessed their effectiveness by comparison with the actual population growth achieved. 3. The magpie robin population doubled from about 25 birds in 1990 to more than 50 by 1995. A simple two-stage demographic model showed that this growth was driven primarily by a significant increase in the annual survival probability of first-year birds and an increase in the birth rate. Neither the annual survival probability of adults nor the probability of a female breeding at age 1 changed significantly over time. 4. Elasticity analysis showed that the annual survival probability of adults had the greatest impact on population growth. There was some scope to use management to increase survival, but because survival rates were already high (> 0·9) this had a negligible effect on population growth. Scope for management analysis showed that significant population growth could have been achieved by targeting management measures at the birth rate and survival probability of first-year birds, although predicted growth rates were lower than those achieved by the recovery programme when all management measures were in place (i.e. 1992-95). 5. Synthesis and applications. We argue that scope for management analysis can provide a useful basis for management but will inevitably be limited to some extent by a lack of data, as our study shows. This means that identifying perceived ecological problems and designing management to alleviate them must be an important component of endangered species management. The corollary of this is that it will not be possible or wise to consider only management options for which there is a demonstrable ecological benefit. Given these constraints, we see little role for elasticity analysis because, when data are available, a scope for management analysis will always be of greater practical value and, when data are lacking, precautionary management demands that as many perceived ecological problems as possible are tackled.

SummaryWe investigated the impact of introduced predators on the productivity of the St Helena Plover Charadrius sanctaehelenae, a shorebird endemic to the South Atlantic island of St Helena. The nest predator species identified have all been introduced to St Helena in the last 510 years, and all are species that are known to be invasive on other islands. The species responsible for taking the largest proportion of eggs was the domestic cat Felis catus, with rats (Rattus rattus or R. norvegicus) and Common Myna Acridotheres tristis taking smaller proportions. Nest survival varied spatially and was correlated with an index of cat density. No relationship was observed between the number of nesting attempts per pair in a year and predator density. The resulting estimates of productivity were insufficient in some areas to allow stable populations to persist locally. Future work should focus on assessing the population level impacts of current and reduced predator densities to St Helena Plovers, and understanding the influence of resource availability and habitat structure on the densities and impacts of predators.

Summary1. Statistical models of population density and/or change in relation to habitat could aid the management of endangered species and help diagnose causes of population decline. Such models seek 'global' explanations for any decline, but endangered species are often vulnerable to highly localized habitat change that can have a significant impact on overall population. In such cases, statistical models can aid in interpreting the impact of localized habitat change on population density and so have a role in diagnosis. We illustrate this approach using data from the endangered St Helena wirebird, a small sand plover endemic to the island of St Helena in the South Atlantic Ocean. 2. The wirebird inhabits pasture habitats and semi-desert areas. Census data suggest that wirebird abundance declined during the early 1990s, from 425 adult birds in 1989 to 335 adult birds by 1998-99. Abundance declined by 34·4% in pasture habitats, whereas abundance in semi-desert increased by 18% over this period. 3. We tested the hypothesis that the decline in abundance in pasture habitats was driven by vegetation change. Multiple regression modelling revealed that wirebird density in pasture was positively correlated with the cover of broad-leaved herbs, but negatively correlated with vegetation height and gorse cover prior to the decline in 1989. A performance test of this model showed that predictions were reliable. 4. The cover of broad-leaved herbs declined significantly between 1989 and 1998-99. However, there was no correlation between the change in wirebird density and the change in broad-leaved herb cover, indicating that this vegetation change was unlikely to have caused the decline in wirebird abundance. 5. The decline in the abundance of wirebirds in pasture habitats was primarily due to changes in three sites. Each experienced site-specific habitat changes, which were likely to cause a decrease in wirebird abundance on the basis of the multiple regression modelling of wirebird density in relation to habitat. We concluded that highly localized vegetation change, rather than general herb cover, played an important role in the overall population decline. 6. Our analysis provides clear habitat management recommendations: pasture management for livestock needs to be compatible with the production of herb-rich grassland, consisting of short vegetation and few woody plants, in order to benefit wirebird conservation. 7. Management decisions for endangered species are often required urgently, and as a result are invariably based on incomplete information, particularly concerning the demographic mechanisms involved in decline. Our approach illustrates a role for simple statistical models under these circumstances. Such models help diagnose the cause of a decline and promote initial, remedial, management actions. This work also shows how habitat effects on endangered species can be highly localized.

SummaryThe Wirebird Charadrius sanctaehelenae, a plover, is the only surviving bird species endemic to the South Atlantic Island of St Helena. The species is currently dependent on habitats that are wholly anthropogenic or extensively modified by human activity. A census carried out during [2005][2006] showed that the Wirebird has undergone a decline of more than 40% over a five-year period to a total of 235 individuals. The species now qualifies for re-classification as 'Critically Endangered'. Vegetation surveys support the results of a previous study in suggesting that the decline may be associated with degradation of the Wirebird's favoured grassland habitat due to reduction of livestock numbers. Predation by introduced mammals and birds is also likely to be a factor but this remains unquantified. The Wirebird may face additional threats to its habitat in the future unless potential tourism-related development associated with the proposed construction of an airport on the island is closely regulated.