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A scarcity of females may constrain population growth of threatened bird species: case notes from the Critically Endangered Raso Lark Alauda razae

  • M. de L. BROOKE (a1), T. P. FLOWER (a1) and M. C. MAINWARING (a2)

Summary

Donald (2007) showed that the adult sex ratios of wild bird populations tended to be male-biased, and that this bias was stronger in threatened species than in those of least concern. Here we show that, in 2004, the world population of the Critically Endangered Raso Lark was 65 individuals, 70% of which were male (adult sex ratio 0.70). In 2008, the population numbered approximately 175 (including juveniles) and the adult sex ratio was 0.58. Both ratios were significantly different from parity. All adult females were observed to be both paired and holding a territory. The observations therefore support Donald’s (2007) suggestion that a shortage of females can be an important constraint on the growth of threatened bird populations, a constraint that needs attention in conservation planning.

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      A scarcity of females may constrain population growth of threatened bird species: case notes from the Critically Endangered Raso Lark Alauda razae
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Copyright

Corresponding author

*Author for correspondence; e-mail: m.brooke@zoo.cam.ac.uk

References

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BirdLife International (2004) Threatened birds of the world. Barcelona and Cambridge: Lynx Edicions and BirdLife International.
Butchart, S. H. M., Stattersfield, A. J. and Collar, N. J. (2006) How many bird extinctions have we prevented? Oryx 40: 266278.
Cramp, S. ed. (1988) The birds of the Western Palearctic. Vol. 5. Oxford: Oxford University Press.
Donald, P. F. (2007) Adult sex ratios in wild bird populations. Ibis 149: 671692.
Donald, P. F. and Brooke, M. de L. (2006) An unlikely survivor: the peculiar natural history of the Raso lark. Brit. Birds 99: 420430.
Donald, P. F., Brooke, M. de L., Bolton, M. R., Taylor, R., Wells, C. E., Marlow, T. and Hille, S. M. (2005) Status of Raso Lark Alauda razae in 2003, with further notes on sex ratio, behaviour and conservation. Bird Conserv. Internatn. 15: 165172.
Komdeur, J. (1992) Importance of habitat saturation and territory quality for evolution of cooperative breeding in the Seychelles warbler. Nature 358: 493495.
Suárez, F., Garcia, J. T., Capriles, E., Calero-Riestra, M., Agirre, A., Justribó, J. H. and Garza, V. (2009) Sex-ratios of an endangered lark after controlling for a male-biased sampling. Ardeola 56: 113118.

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