Trends and Factors in the Global Endangerment of Birds

Birds To Watch 2

A total of 1,111 bird species (11% of the world's avifauna) have been identified as threatened, with a further 11 (0.1%) being allocated to the category of Conservation Dependent, 66 (1%) to Data Deficient and 875 (9%) to Near-threatened (Figure 1). In other words, over a fifth of all bird species give some cause for concern in terms of global extinction risk. If to this we add the consideration that high levels of the remaining 80% are declining in overall numbers-in Europe 25% of species have experienced a decline of more than 20% in over one-third of their populations in the past 20 years (Tucker and Heath 1994), which intimates the likely situation in many other regions-and, further, that these levels will almost certainly be reflected in all other terrestrial life-form groups (for evidence of which see Groombridge 1993b), then the future of the planet's biological diversity is nothing if not bleak.

Figure 1. Proportions of the world's bird species in the different categories of risk.

Of the 1,111 threatened bird species, four (0.4%) are identified as Extinct in the Wild, 168 (15%) as Critical, 235 (21%) as Endangered and 704 (63%) as Vulnerable (Figure 2). The Extinct in the Wild, Critical and Endangered species form the subject of Appendix 3 and of a species-by-country review (Box 1).

Figure 2. Proportions of the world's bird species in the different threatened categories.

Given that the threat categories are characterized by different probabilities of extinction (50% chance in five years for Critical, 20% in 20 years for Endangered, 10% in 100 years for Vulnerable; see Figure 1 on p. 14), it is possible to calculate the number and rate of avian species extinctions over the next 100 years, assuming no action is taken on their behalf, and making no allowance for new species entering the lists (Figure 3). From this it emerges that over 400 bird species are likely to die out in the next hundred years; but far more disturbing is the anticipation that 200 will disappear in the next 20 years, 100 of them in the next 5-10. Intuitively, however, this scenario appears too extreme: as we have already pointed out under 'Thresholds for Critical' (p. 19), there is a condition which satisfies a criterion for this category which does not truly reflect a 50% chance of extinction in five years. Nevertheless, the basic point cannot be sidestepped: only concerted action at key points across the globe is now going to prevent a major wave of species losses.

Figure 3. Future extinction trajectory of threatened birds as predicted by the population viability criteria. This analysis does not factor in species entering the list over time, or the categories into which they will fall.

Use of criteria

Apart from the population viability analysis criterion (code E; not used at all, as explained on p. 20), the other criteria (codes A-D) were all used extensively in the triggering of threatened status, most usually in combination rather than singly (Figure 4). The commonest way in which bird species have been judged to be at risk is by their possessing a declining population numbering less than 10,000 mature individuals (code C). No fewer than 764 species out of 1,111 (almost 70%) are believed to exhibit this characteristic, and over 100 of them qualify on this criterion alone. This does not mean that good population data are available, rather that reasonable inference from the evidence often allows a judgement against the threshold in question.

Figure 4. Distribution of criteria amongst the threatened species.

The other notable feature of Figure 4 is the influence exerted by the population and range-size stand-alone criteria, both of which reflect the view that a species is inherently at risk, irrespective of any threat (actual or potential), if it falls below a certain level in terms of either numbers of individuals or the area it occupies. Eighty-six species (c.8%) qualify on the range-size criterion (D2) alone.

Distribution

An analysis of species by geopolitical unit (Appendix 1) and subsequent ranking (Box 1 and Appendix 2, p. 342) places Indonesia, Brazil and the Philippines in the top three countries for total numbers of threatened species (all categories), with China, India, Colombia, Peru and Ecuador in the next five positions. It is notable that the great majority of the land surface of the New World and Asia features in the first 25 geopolitical units (together contributing 19 units), whereas only a small proportion of Africa is registered through three countries, none of them in the top 20 (Box 1, column A). This reflects the relative species-richness and higher levels of local endemism in the Oriental and particularly the Neotropical regions when compared with the Afrotropical, and perhaps also indicates the fragility of the situation in Asia, where roughly 60% of the human population of the planet is concentrated.

When only the higher categories of threat (i.e. Extinct in the Wild, Critical, Endangered) are considered (Box 1, column B), the dominance of the New World and Asia is further increased (20 units), with only Madagascar remaining from Africa among the top 25. The high degree of vulnerability of island avifaunas also emerges in the upward progress of the U.S.A. (which includes Hawaii), Mexico (which includes the Revillagigedos and Guadalupe), French Polynesia and the Solomons.

If these latter figures are yet further refined to score for national endemics only (Box 1, column C), the order changes more dramatically, again with many small island units (French Polynesia, Mauritius, Cuba, Seychelles, New Caledonia, Micronesia, Comoros) pushing higher upwards and several previously leading countries (China, India, Ecuador) dropping sharply. Most notable is the emergence of the Philippines as of exceptional significance, followed by Brazil and Colombia, and it is fairly startling to see that four of the five top places in this list are occupied by nations of the New World.

It may not always be appropriate to use levels of national endemism as a measure of priority, but the global conservation community needs to know where unique assemblages of biological diversity lie (as indeed do the parties to the Convention on Biological Diversity, which commits them to the preparation of national conservation strategies). Moreover, weighting for complementarity certainly revives the challenge inherent in the concept of 'ultimate responsibility'. For example, analysis of Threatened birds of the Americas reveals the almost total absence of overlap in threatened species complement between Brazil, Peru, Colombia and Mexico, the first two accounting for 50%, the first three for 66% and all four for 75% of the threatened birds of the New World (Collar et al. in press).

Differences between insular and continental areas were to be expected, with much higher total proportions of avifaunas being at risk on islands, through the influence of introduced predators and competitors. The elevated importance of islands for threatened birds, long recognized (King 1978, 1985, Temple 1986), is certainly reaffirmed here; however, the issue is relatively complex for a variety of reasons, and an analysis of globally threatened island birds will have to be undertaken elsewhere.

Habitats and threats

The simple system of coding species for broad habitat types and threats, giving these habitats and threats equal weight where multiple types are allocated (see Appendix 1, p. 243, for classification), reveals similar results to previous analyses (e.g. King 1978, Temple 1986), reinforcing forest as the most important habitat (well over 50%) for threatened birds (Figure 5), and habitat loss and degradation as the most significant threat (almost exactly 50%) worldwide (Figure 6). The importance of forest is probably slightly downplayed in this analysis, as it is likely to be the more significant habitat for many species that range through several types. The seemingly rather strong presence of scrub in the habitat breakdown probably reflects the use of this descriptor to cover a wide variety of dryland and secondary habitats, and in many cases the species involved are likely to use forest as well.

Figure 5. Habitats of threatened bird species. `Other' habitats comprise savanna 1.1%, introduced/exotic vegetation 1.0%, deserts 0..5%, urban 0.1% and unknown 0.9%.

Figure 6. Threats affecting threatened bird species (see text for explanation of analysis). `Other' threats comprise disturbance by humans and livestock (1.5)%, pollution, pesticides and accidental poisoning (1.3%) and fisheries (0.3%).

Given this, it is perhaps surprising that as little as 50% of the threat burden derives from habitat destruction. This may reflect the weighting procedure described above, when in many cases habitat loss may be by far the most important threat but has been allocated equal status with all other threats. This effect will have been compounded by the influence in the criteria of small ranges and small populations, the stand-alones that can trigger threatened status even if no actual or potential threat has been identified (see 'Use of Criteria', above); Figure 6 shows that these two contribute about a quarter of the burden of threats to all threatened birds.

The general habitat classification and analysis detailed above could be refined by subdividing several of the categories, notably forest, to take into account variations in habitat type related to altitude, climate, soil and other environmental variables. Such a review was not attempted here because of the difficulties inherent in devising a detailed habitat classification at the global level and because of time constraints. Further analysis of the data in Appendix 1 will, of course, be possible, for example by making comparisons between families, or (with a little further work) between guilds or size-classes of species. A review of the parrots (Wirth et al. in press), requested several months before the finalization of the book, confirmed the prominence of trade amongst the threats to the family, although even then habitat destruction affects twice as many members of the family.

Changes between 1988 and 1994

A total of 1,030 bird species was considered threatened with global extinction in 1988 (Collar and Andrew 1988). This figure has increased to 1,111 in the present study, a rise of only 81 (c.8%), much of which might appear attributable to taxonomic changes. However, the new list does not simply consist of the old list with 81 additions. As Table 1 indicates, the similarities between the two lists are far greater than the differences, but the differences require consideration. Analysis (Tables 2 and 3) shows the crucial role played by improved knowledge of the status of the many species under review in these works (a point already brought out in a comparison of the first Birds to watch and Threatened birds of the Americas by Bibby 1994). Thus, of the 214 species unique to the 1988 list, 140 became Near-threatened (mainly-although this is not stated-through improved information) and a further 13 disappeared altogether from consideration as at risk; this accounts for over 70% of the species in question. Similarly, of the 295 species unique to the 1994 list, 93 have moved up from Near-threatened (again, mainly through improved information), 85 are elevated from their previous but erroneous position in Low Risk (these are species for which there had been no easily accessible evidence of threat before, but which we now know were then at risk), and 10 have genuinely deteriorated from what is now called Low Risk status six years ago; this accounts for 64% of the species in question.

The impression from Table 2 that 16 species have become extinct during the last six years is, of course, misleading; there was no separate Extinct Species list in the 1988 edition of Birds to watch and all 16 were retained as threatened in that book in the hope that they might yet be found to persist; in fact only one, the Ivory-billed Woodpecker Campephilus principalis, at that stage appeared likely to be extant. Essentially, therefore, these 16 should be discounted as a source of difference in the two lists. The same is true of the 25 species which have transferred to Data Deficient, since their presence in the first Birds to watch resulted from qualifying-although individual categories were not explicit in that book-under the old IUCN category Insufficiently Known (which, under an earlier version of the precautionary principle, was interpreted as denoting threatened status); so they are all products of a particular change in the criteria.

Two important influences behind the changes between lists derive from taxonomic developments and from the range-size stand-alone (D2). The importation of 80 species into the 1994 list on taxonomic grounds (which includes a number of newly described birds) indicates the abiding need for conservation to keep in close contact with systematics. The addition of 27 species through changes in the criteria certainly stems in large part from the requirement to list species whose ranges are less than 100 km2 in extent, where before this was a matter of discretion (which is not to say that we find this criterion problematic).

One of the most disheartening features of the table is the fact that active intervention has caused not a single species to move from threatened status into Low Risk (beyond that part of Low Risk we have labelled Near-threatened). It is, of course, true that any threatened species under active management is far more likely to move out of threatened status only as far as Conservation Dependent, yet there are only seven such species, and even in those cases perhaps only three have earnt their new status as a result of active management instituted in the past six years.

A seemingly more optimistic interpretation, based on this comparison between studies (and indeed on broader experience gained in researching this and other books), is that the earth tends to be more resourceful than we are able to judge it: if 153 of 1988's threatened species have been shown by improved knowledge not to be so, then many others may also be faring better than was once believed. It is certainly true that bird populations tend to prove larger than the educated guesses of desk-bound researchers reviewing what little evidence they can muster. All the same, such findings are no cause for complacency, and indeed the hope they may engender is largely illusory: the earth is finite, and the upgrading of species, often to just beyond a threshold they were once thought to have passed, is no more than to find them the smallest of spaces in which, unless the category Near-threatened is taken seriously, they will quite probably be ignored until they are once more deemed to have reached the level at which emergency responses are required.

Conclusions

This is the first time the new IUCN criteria have been used on a complete class of animals. They bring rigour, objectivity and accountability to the difficult process of threatened species analysis. However, the relatively high proportion of species shared between Birds to watch in 1988 and 1994 prompts the unorthodox consideration that the old IUCN criteria were, in fact, capable of working efficiently, just so long as they were applied reasonably and responsibly; moreover, they were short and simple. The problem with them was that their vagueness was an invitation to misuse, and this (in our view) allowed the distortion of the red-listing process through the undue influence of flagship species, 'sacred cows' and other inappropriate elements. The new criteria, unwieldy though they are, with their various thresholds, qualifiers, definitions and explanations, greatly reduce the opportunities for such misuse; they, too, have necessarily vague areas and require assumption and inference, often on a very informal basis, but they establish a framework which tends to contain and reduce subjectivity and renders the whole process of assessment more accountable. We therefore warmly commend them to IUCN and other potential users, and encourage the Species Survival Commission specialist groups to adopt them when reviewing the taxa in their charge.

Despite this, and indeed despite our emphasis above on the relative insignificance of the disparity between the 1988 and 1994 listings, it is a certain conclusion of this entire exercise that assessment of status becomes both more accurate and more feasible in proportion not only to the quality but also to the applicability of available data. Put more simply, solid information makes for sound judgement. In this sense, the changes that have occurred since 1988 may in many cases be linked to advances in the Red Data Book and associated BirdLife research programmes: work on Threatened birds of the Americas, Putting biodiversity on the map and the forthcoming Global directory of endemic bird areas (Stattersfield et al. in prep.) have between them pulled together high-resolution data on 2,759 species of bird around the world (28% of all bird species). Moreover, the African and American RDBs precipitated fieldwork on rare species (in many cases even before the books were published), and of course the first Birds to watch played a key role in highlighting many other cases (the BirdLife Indonesia Programme, a major contributor to this its replacement, actually grew out of its findings). The result of all these exercises has been a constant stream of new information on birds in what are biologically the lesser known parts of the world, feeding in from and back out to the networks of BirdLife contacts in an ever-strengthening loop of understanding and commitment.

Birds to watch 2 has, we hope, continued the process. The preservation of the species in this book (including those that are Data Deficient and Near-threatened) is a major challenge to the great body of ornithologists and conservationists that lies both within and beyond the formal BirdLife network. Part of that challenge can be met, as we indicated at the start of this introduction (under 'Birds to watch in Context'), by the strategic use of areas of overlap between the species. BirdLife has already identified 'Endemic Bird Areas' through its Biodiversity Project (ICBP 1992, Stattersfield et al. in prep.), key forests for threatened Afrotropical birds (Collar and Stuart 1988), key sites for threatened Neotropical birds (Wege and Long in prep.), 'Important Bird Areas' in both Europe (Grimmett and Jones 1989) and the Middle East (Evans 1994), and there is now a commitment to identify all the planet's IBAs, according to standard criteria, by the year 2000. There will always, however, be bird species beyond easy reach of the area-based approach, and their conservation by other means (species-specific intervention, policy implementation, legal enforcement) forms the other main part of the challenge. In many cases, the framework for such action is already in place, so that what is needed is mainly direction and motivation, through advocacy and example.

The ideal is that nothing should slip through the net. Red Data Books exist to prevent this from happening. This is their central and abiding contribution to the biodiversity initiative of the late twentieth century. All the same, as we noted at the outset (p. 8), the best guarantee against slipping the net is the use of a blanket. Stewardship of this planet-its ecologically sound management and development-requires very much more from us than the cradling of the most vulnerable of its life-forms (vital though this be); and that requirement, and all that it entails, is the strongest challenge of them all.

Box 1. Geopolitical units ranked by their numbers of threatened species.

Under A and B, where units are ranked above others with the same score, this is because weighting has been given either to the threatened species total (in B) or to the degree of endangerment within the species total (in A). Under C, priority where scores are tied has been given to units with higher numbers of endemic species categorized as Vulnerable or as Near-threatened. See also Appendix 2 (p. 342).

A
1. (104) Indonesia
2. (103) Brazil
3. (86) Philippines
4. (86) China
5. (71) India
6. (62) Colombia
7. (60) Peru
8. (50) Ecuador
9. (46) U.S.A.
10. (45) Vietnam
11. (45) New Zealand
12. (44) Thailand
13. (44) Australia
14. (43) Myanmar
15. (40) Argentina
16. (35) Russia
17. (34) Mexico
18. (31) Japan
19. (31) Malaysia
20. (31) Papua New Guinea
21. (30) Tanzania
22. (28) Madagascar
23. (28) Bangladesh
24. (27) Bolivia
25. (26) Zaïre
 

B
1. (47) Brazil
2. (45) Philippines
3. (31) Colombia
4. (25) U.S.A.
5. (20) Indonesia
6. (20) Mexico
7. (18) Peru
8. (16) Vietnam
9. (16) Ecuador
10. (16) Argentina
11. (13) China
12. (13) India
13. (13) New Zealand
14. (12) Australia
15. (11) Thailand
16. (11) Japan
17. (11) Venezuela
18. (10) Madagascar
19. (10) Cuba
20. (10) Paraguay
21. (9) Solomon Islands
22. (9) French Polynesia
23. (8) Myanmar
24. (8) Malaysia
25. (8) Bolivia
 

C
1. (40) Philippines
2. (32) Brazil
3. (24) Colombia
4. (17) U.S.A.
5. (13) Mexico
6. (12) Indonesia
7. (12) New Zealand
8. (11) Australia
9. (10) Madagascar
10. (9) Peru
11. (7) French Polynesia
12. (7) Venezuela
13. (6) Ecuador
14. (6) Mauritius
15. (6) Cuba
16. (5) Vietnam
17. (5) Angola
18. (5) Kenya
19. (5) Somalia
20. (4) India
21. (4) Ethiopia
22. (4) Seychelles
23. (4) New Caledonia
24. (4) Micronesia
25. (4) Comoros
 

Table 1. Changes in the numbers of threatened bird species between 1988 and 1994.

Table 2. Numbers of species downgraded from threatened status between 1988 and 1994, with reasons.

Table 3. Numbers of species upgraded to threatened status between 1988 and 1994, with reasons.

This information comes from Birds to Watch 2: (The World List of Threatened Birds), NJ Collar, MJ Crosby and AJ Stattersfield (1994) BirdLife, Cambridge. This is the official source for birds on the IUCN Red List.

BirdLife is interested in hearing about new information or references on threatened species. See contact details at the end of this page.

Birds to Watch 2 and other publications are available for purchase from Natural History Book Service, email nhbs@nhbs.co.uk, http://www.nhbs.com.

For further information please write to: Wellbrook Court, Girton Road, Cambridge, UK CB3 ONA Tel: +44 1223 277318 Email: redlist@birdlife.org Document URL: http:// www.unep-wcmc.org /species/data/birdlife/btw3.htm Revision date: -September-2007 Current date: -May-2008 Comments © BirdLife