INTRODUCTION

The identification of the most threatened species and the prioritisation of the most important sites for protection are, and will remain, essential to the conservation of bird biodiversity (Chapters 4 and 5). The uneven distribution of threatened biodiversity is highlighted by the fact that less than 5% of the Earth's land surface holds almost 75% of the world's threatened bird species (BirdLife International 2000).

On a global scale, however, protected areas are small; nationally protected areas cover less than 5% of the Earth's land surface and far less of marine habitats (Ryan 1992). It is generally accepted that site protection is inadequate to conserve existing populations of the majority of species whose ranges fall largely outside such areas (e.g. Pain & Dixon 1997). Some protected areas may even be insufficient to conserve those (often threatened) species for which they were designated. Relatively little work has been conducted on the long-term viability of such populations, especially important when reserves are isolated, although this is an expanding area of research (see Chapter 5). In addition, protected status is often nominal rather than actual, especially in areas where the needs of local communities are in real or perceived conflict with the objectives of environmental protection (Terborgh 1999).

Reserves cannot be viewed in isolation, as many activities and population processes taking place outside protected areas can adversely affect conditions for species within protected areas (e.g. Baillie et al. 2000).

The death of a pigeon called Martha in Cincinnati Zoo on 1st September 1914 was a significant event. She was the last passenger pigeon (Ectopistes migratorius) in existence. In 1878 the total population of passenger pigeons was estimated at 50 million birds, roaming the forests of the eastern United States. By March 1900, the last individual was killed in the wild (see Wilcove 1999). Although the dodo (Raphus cucullatus) of Mauritius has become a symbol of extinction and the efforts of conservationists to save endangered species, the story of the passenger pigeon is probably a starker example of the capacity of human activities to threaten the Earth's biodiversity.

Sadly, the passenger pigeon is not an isolated example. In its latest assessment, BirdLife International describes 1,186 species of bird that are currently threatened with extinction worldwide. A total of 128 species are believed to have become extinct in the last 500 years, 103 of these since 1800 (BirdLife International 2000). The rate at which bird species are being lost is currently much more rapid than at any time in the evolutionary history of this group (F.D.M. Smith et al. 1993; Pimm et al. 1995). The loss of biodiversity is not just the random deletion of species – certain families are more at risk than others. This bias in the extinction process means we are not just losing individual bird species, but significant parts of the Earth's evolutionary history (e.g. Purvis et al. 2000).