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1 January 2010 Balanced Sex Ratio at Hatch in a Greater Sage-Grouse (Centrocercus urophasianus) Population
Michael T. Atamian, James S. Sedinger
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Only one estimate of sex ratio at hatch exists for Greater Sage-Grouse (Centrocercus urophasianus). Managers typically assume a ratio at the population level of approximately 2:1 (female:male), primarily on the basis of sex ratio in the harvest. We determined the sex of newly hatched young and unhatched Greater Sage-Grouse by amplifying a portion of the sex-linked CHD gene. Sex ratio for Greater Sage-Grouse in east-central Nevada was 0.51 ± 0.03 (SE; n = 272). We found no substantial difference in size between eggs that produced male chicks and those that produced females (44.5 ± 0.2 mm3 vs. 44.3 ± 0.3 mm3) or between the masses of male and female chicks (25.8 ± 0.3 g vs. 26.3 ± 0.3 g), which suggests that energetic cost investments by females were similar between offspring of different sexes. We also found no effect of female condition on differential investment in male versus female offspring. Given that adult survival does not differ substantially between the sexes in our study population (J. S. Sedinger unpubl. data), we suggest that this population may not contain 2 adult females to 1 adult male and that any bias in adult sex ratio is likely attributable to differential survival from hatch to first breeding.

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Michael T. Atamian and James S. Sedinger "Balanced Sex Ratio at Hatch in a Greater Sage-Grouse (Centrocercus urophasianus) Population," The Auk 127(1), 16-22, (1 January 2010).
Received: 10 February 2009; Accepted: 1 June 2009; Published: 1 January 2010
Centrocercus urophasianus
genetic sexing
greater sage-grouse
parental investment
sex ratio
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