Taxonomic bias has been documented in general science and conservation research publications. We examined whether taxonomic bias is similarly severe in actual conservation programmes as indicated by the focus of species reintroduction projects worldwide. We compiled a database of reintroduction projects worldwide, yielding a total of 699 species of plants and animals that are the focus of recent, current or planned reintroductions. Using IUCN (World Conservation Union) data for total numbers of known species worldwide, we found that vertebrate projects were over-represented with respect to their prevalence in nature. Within vertebrates, mammals and, to a lesser extent, birds, were over-represented, whereas fish were underrepresented. This over-representation extended to two mammal orders, artiodactylids and carnivores, and to four bird orders, anseriforms, falconiforms, gruiforms and galliforms. For neither mammals nor birds was reintroduction project bias related to any differences between orders in vulnerability to threat. Bird species that are the focus of reintroduction efforts are more likely to be categorised as 'Threatened' than expected on the basis of the distribution of all known species over all threat categories, however, nearly half of all bird species being reintroduced are classified as 'Least Concern'. The selection of candidates for reintroduction programmes is likely to consider national priorities, availability of funding and local community support, over global conservation status, While a focus on charismatic species may serve to garner public support for conservation efforts, it may also divert scarce conservation resources away from taxa more in need of attention.

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Humans depend on biodiversity in myriad ways, yet species are being rapidly lost due to human activities. The ecosystem services approach to conservation tries to establish the value that society derives from the natural world such that the true cost of proposed development actions becomes apparent to decision makers. Species are an integral component of ecosystems, and the value they provide in terms of services should be a standard part of ecosystem assessments. However, assessing the value of species is difficult and will always remain incomplete. Some of the most difficult species' benefits to assess are those that accrue unexpectedly or are wholly unanticipated. In this review, we consider recent examples from a wide variety of species and a diverse set of ecosystem services that illustrate this point and support the application of the precautionary principle to decisions affecting the natural world.

Between the years 1994 and 2000, we assessed the mortality rate of adult-sized, migrant Asian houbara bustards (Chlamydotis [undulata] macqueenii) via banding and satellite tracking programmes. The birds were captured either on their breeding grounds in Kazakhstan (Taukum desert and Buzachi peninsula) and in China (Jungar basin) or on their wintering grounds in Pakistan (Cholistan desert) and in the United Arab Emirates (Baynunah area). For the banding programme, 104 houbara bustards were marked and statistical analysis was performed on the number of transmitters and rings returned by falconers. This allowed us to calculate a 0.045 (SD 0.061) annual mortality rate attributable to hunting activities. The tracking programme analysed the fate of 41 houbara bustards equipped with satellite transmitters (PTTs). Overall, the satellite-tracked birds were followed for 10,965 days and had travelled all over the distribution range of the species in Asia. The causes of mortality were assessed from the interpretation of the ARGOS data relayed by the sensors embarked on the PTTs. The annual mortality rate was derived from the calculation of the average finite daily survival rate using the Trent & Rongstad (1974) method. With this method, the overall annual mortality rate in adult-sized houbara bustards migrating through Asia was 0.283 (95%lcl 0.186-95%ucl 0.404). The hunting and poaching pressure could explain 73.5% of the observed mortality. The mortality rate during winter, when the houbara is under severe hunting pressure, was 11.2 times higher than during the breeding season. Houbara appear to be especially at risk in Pakistan, Afghanistan and Iran. A VOR-TEX simulation showed that under current hunting and poaching pressures, the probability of extinction of the houbara population modelled can be anticipated at 50 years with a 94% probability. The maximum sustainable yield was estimated at 7.2% of the adult-sized population whereas as much as 20.8% is currently taken. This work stresses the need for conservationists and Arab falconers to take appropriate concerted measures as soon as possible.

Information on migratory pathways and connectivity is essential to understanding population dynamics and structure of migrant species. Our manuscript uses a unique dataset, the fruit of 103 individual Asian houbara bustards captured on their breeding grounds in Central Asia over 15 years and equipped with satellite transmitters, to provide a better understanding of migratory pathways and connectivity; such information is critical to the implementation of biologically sound conservation measures in migrant species. At the scale of the distribution range we find substantial migratory connectivity, with a clear separation of migration pathways and wintering areas between western and eastern migrants. Within eastern migrants, we also describe a pattern of segregation on the wintering grounds. But at the local level connectivity is weak: birds breeding within the limits of our study areas were often found several hundreds of kilometres apart during winter. Although houbara wintering in Arabia are known to originate from Central Asia, out of all the birds captured and tracked here not one wintered on the Arabian Peninsula. This is very likely the result of decades of unregulated off-take and severe habitat degradation in this area. At a time when conservation measures are being implemented to safeguard the long-term future of this species, this study provides critical data on the spatial structuring of populations.

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