Table 3. Extinction-prone bird groups

Category

% extinction-prone (P)

Island species (2,296)

44.1 (<0.0001)

Sedentary (nonmigrant; 6,591)

25.5 (<0.0001)

Altitudinal range ≤500 m (2,339)

35.2 (<0.0001)

≤500 m a.s.l. (1,886)

31.3 (<0.0001)

≥3,000 m a.s.l. (156)

26.5 (<0.01)

Body mass > 1,000 g (475)

38.5 (<0.0001)

One egg clutch (454)

33.0 (<0.0001)

Monotypic genera (868)

25.2 (<0.0001)

≤5 species in family (130)

33.8 (<0.0001)

Described since 1993 (305)

57.7 (<0.0001)

The global percentage of bird species that are extinction-prone is 20.7%. Near-threatened, threatened, and extinct species are considered extinction-prone. P values are for χ2 comparisons with the global distribution. Migration status of 7 species, altitudinal distributions of 113 species, body masses of 2,598 species, and clutch sizes of 3,927 species are unknown. Species described since 1993 are those not included in the Sibley– Monroe list (1, 2) but accepted by BirdLife International. a.s.l., above sea level. Note that some of these variables are correlated and not independent. See Supporting Table 4 for Pearson correlation coefficients. Refs. 3–11, among others, provide good examples of the literature on the correlates of threat of extinction in bird species.

1. Sibley, C. G. & Monroe, B. L. (1990) Distribution and Taxonomy of Birds of the World (Yale Univ. Press, New Haven, CT).

2. Monroe, B. L. & Sibley, C. G. (1993) A World Checklist of Birds (Yale Univ. Press, New Haven, CT).

3. Gaston, K. J. & Blackburn, T. M. (1995) Philos. Trans. R. Soc. London B 347, 205–212.

4. Bennett, P. M. & Owens, I. P. F. (1997) Proc. R. Soc. London B 264, 401–408.

5. Gaston, K. J. & Blackburn, T. M. (1997) Evol. Ecol. 11, 557–565.

6. Russell, G. J., Brooks, T. M., McKinney, M. M. & Anderson, C. G. (1998) Conserv. Biol. 12, 1365–1376.

7. Manne, L. L., Brooks, T. M. & Pimm, S. L. (1999) Nature 399, 258–261.

8. Owens, I. P. F. & Bennett, P. M. (2000) Proc. Natl. Acad. Sci. USA 97, 12144–12148.

9. Manne, L. L. & Pimm, S. L. (2001) Anim. Conserv. 4, 221–229.

10. von Euler, F. (2001) Proc. R. Soc. London B 268, 127–130.

11. Gage, G. S., Brooke, M. D., Symonds, M. R. E. & Wege, D. (2004) Anim. Conserv. 7, 161–168.