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Population sex ratio shift from fledging to recruitment: consequences for demography in a philopatric seabird

Population sex ratio shift from fledging to recruitment: consequences for demography in a philopatric seabird
Population sex ratio shift from fledging to recruitment: consequences for demography in a philopatric seabird
In many dimorphic bird species, offspring sex ratio is skewed towards the production of the smaller sex. Offspring sex ratio can be biased in monomorphic birds however, and the demographic consequences of such bias are unknown. Sex-specific mortality and dispersal are fundamental mechanisms of sex ratio adjustment at the population level, but evidence for adjustments is weak and feedback into population dynamics poorly understood. Here, we link sex ratio at fledging with sex-specific subadult return and recruitment at the Banter See common tern Sterna hirundo colony. Using molecular sexing methods and a remote detection system, we permanently tracked individuals from four complete cohorts (n=1171 fledglings) across these life-history stages at their natal colony site, which permitted a structured analysis of sex ratio across multiple seasons. Sex ratio shifted significantly from significant daughter dominance at fledging to higher proportions of natal males among recruits; return and recruitment rates of sons were significantly higher than daughters (p?0.002). No significant between-year differences were detected. 47.4% of natal male recruits were paired with a non-natal female, but only 37.0% of natal female recruits had a non-natal partner. Elasticity analysis suggested that natal males have a greater influence on natal population growth rate than natal females. Sex biased dispersal is the most probable reason for these results indicating higher emigration to and immigration from other colonies in females, the less territorial and less philopatric sex. This pattern may be related to different gender roles in parental duties and with respect to competition for local resources.
0030-1299
60-68
Becker, Peter H.
3fe56473-d701-4a54-badf-9d29b346bb25
Ezard, Thomas H.G.
a143a893-07d0-4673-a2dd-cea2cd7e1374
Ludwigs, Jan-Dieter
fb2ec285-4834-4e52-b103-ae0295ba047c
Sauer-Gürth, Hedwig
adc937ef-214d-49d0-93f5-c9ebcb5dc652
Wink, Michael
3aaff453-4cf5-461b-b284-60936c33490e
Becker, Peter H.
3fe56473-d701-4a54-badf-9d29b346bb25
Ezard, Thomas H.G.
a143a893-07d0-4673-a2dd-cea2cd7e1374
Ludwigs, Jan-Dieter
fb2ec285-4834-4e52-b103-ae0295ba047c
Sauer-Gürth, Hedwig
adc937ef-214d-49d0-93f5-c9ebcb5dc652
Wink, Michael
3aaff453-4cf5-461b-b284-60936c33490e

Becker, Peter H., Ezard, Thomas H.G., Ludwigs, Jan-Dieter, Sauer-Gürth, Hedwig and Wink, Michael (2008) Population sex ratio shift from fledging to recruitment: consequences for demography in a philopatric seabird. Oikos, 117 (1), 60-68. (doi:10.1111/j.2007.0030-1299.16287.x).

Record type: Article

Abstract

In many dimorphic bird species, offspring sex ratio is skewed towards the production of the smaller sex. Offspring sex ratio can be biased in monomorphic birds however, and the demographic consequences of such bias are unknown. Sex-specific mortality and dispersal are fundamental mechanisms of sex ratio adjustment at the population level, but evidence for adjustments is weak and feedback into population dynamics poorly understood. Here, we link sex ratio at fledging with sex-specific subadult return and recruitment at the Banter See common tern Sterna hirundo colony. Using molecular sexing methods and a remote detection system, we permanently tracked individuals from four complete cohorts (n=1171 fledglings) across these life-history stages at their natal colony site, which permitted a structured analysis of sex ratio across multiple seasons. Sex ratio shifted significantly from significant daughter dominance at fledging to higher proportions of natal males among recruits; return and recruitment rates of sons were significantly higher than daughters (p?0.002). No significant between-year differences were detected. 47.4% of natal male recruits were paired with a non-natal female, but only 37.0% of natal female recruits had a non-natal partner. Elasticity analysis suggested that natal males have a greater influence on natal population growth rate than natal females. Sex biased dispersal is the most probable reason for these results indicating higher emigration to and immigration from other colonies in females, the less territorial and less philopatric sex. This pattern may be related to different gender roles in parental duties and with respect to competition for local resources.

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More information

e-pub ahead of print date: 11 October 2007
Published date: January 2008
Organisations: Environmental

Identifiers

Local EPrints ID: 344732
URI: https://eprints.soton.ac.uk/id/eprint/344732
ISSN: 0030-1299
PURE UUID: 0eb2bbe1-f9f5-4d55-9811-9cc1b7a76ab8
ORCID for Thomas H.G. Ezard: ORCID iD orcid.org/0000-0001-8305-6605

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Date deposited: 31 Oct 2012 09:45
Last modified: 15 Aug 2019 00:35

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