Sexual Dimorphism and use of Morphological Measurements to Sex Adults, Immatures and Chicks of Rockhopper Penguins

Poisbleau, Maud; Demongin, Laurent; Noordwijk, Hendrika J. van; Strange, Ian J.; Quillfeldt, Petra

doi:10.5253/078.098.0212

Cited by 43 publications

(56 citation statements)

References 19 publications

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“…date of laying onset) and the corresponding 60 males from six to eight days after their female partner. The sex of birds was determined from bill measurements within pairs, the bill being larger in males than females [50]. It was also verified from previous determinations (morphological and genetic) according to the transponder number.…”

Section: Methodsmentioning

confidence: 85%

Females Paired with New and Heavy Mates Reduce Intra-Clutch Differences in Resource Allocation

Poisbleau

Dehnhard²,

Demongin³

et al. 2013

PLoS ONE

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Reproductive investment affects both offspring and parental fitness and influences the evolution of life histories. Females may vary their overall primary reproductive effort in relation to the phenotypic characteristics of their mate. However, the effects of male quality on differential resource allocation within clutches have been largely neglected despite the potential implications for mate choice and population dynamics, especially in species exhibiting biparental care and brood reduction. Female southern rockhopper penguins Eudyptes chrysocome paired with heavy mates reduced intra-clutch variation in egg and albumen masses. Females paired with new mates also reduced intra-clutch variation in yolk androgen levels. Since both an increased mass and increased androgen concentrations positively influence chick survival under sibling competition, the chances of fledging the whole clutch are likely to be higher for newly formed pairs with heavy males than for previously formed pairs with light males. Interestingly, total clutch provisioning did not vary with male quality. We show for the first time that females vary intra-clutch variation in resource allocation according to male quality. In species with brood reduction, it may be more adaptive for females to modulate the distribution of resources within the clutch according to breeding conditions, than to change their total clutch provisioning.

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Section: Methodsmentioning

confidence: 85%

Females Paired with New and Heavy Mates Reduce Intra-Clutch Differences in Resource Allocation

Poisbleau

Dehnhard²,

Demongin³

et al. 2013

PLoS ONE

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“…Most other studies using similar discriminant analyses to separate sexes of spheniscids with > 90% confidence also relied on beak measurements (e.g. bill length and depth for rockhopper penguins, Poisbleau et al 2010). However, the functions generated may not always be applicable to the entire range of the species, because vari ability in morphology can arise from geographic variation or even inter-observer bias (see Renner et al 1998, Vanstreels et al 2011).…”

Section: Use Of Bill Length and Bill Depth For Sexing African Penguinsmentioning

confidence: 99%

Sex-specific foraging behaviour and a field sexing technique for Endangered African penguins

Pichegru

Cook²,

Handley³

et al. 2013

Endang. Species. Res.

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Sexual differences in at-sea behaviour of seabirds often derive from size dimorphism and may lead to both resource partitioning and diverging threats between the sexes. Spheniscids are among the least dimorphic of the seabird families and are the most threatened. In many instances, diet differs between the sexes in penguins, but few studies have compared their foraging behaviour, partly because of the difficulty of identifying sexes in the field. We derived a discriminant function analysis that predicts the sex of African penguins Spheniscus demersus with > 90% confidence, using only beak length and depth. We also deployed GPS-time-depth recorders on male and female penguins breeding on 2 of their largest colonies in South Africa over 2 consecutive breeding seasons and compared their at-sea behaviour. Foraging effort (time spent at sea, distance covered) showed greater variance with clutch mass and between years and colonies than between sexes. However, although maximum diving capabilities were similar, males dived deeper and longer on average than females. Females compensated by increasing their diving frequency, which resulted in similar volumes of water being explored, and foraged over larger foraging areas. There was also some spatial separation between sexes, although foraging range overlap differed markedly (35 to 83%) between years and islands, presumably reflecting prey availability and the need to minimise between-sex competition. The results suggest potential niche partitioning between the sexes in African penguins, but could also be a passive consequence of sexual dimorphism driven primarily by sexual selection. Female behaviour may make them more at risk from predation or oiling events, highlighting the possibility of sex-dependent vulnerability in this Endangered species.

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“…Flipper length (extended from axilla) was measured with a ruler to the nearest millimetre. Bill length (exposed culmen) and bill depth (at junction of gonys and inter-ramal region) were measured to the nearest 0.1 mm using callipers (following Poisbleau et al 2010). Penguins were weighed with an electronic balance to the nearest 20 g. Sex was determined using morphological measurements (Poisbleau et al 2010).…”

Section: Study Area and Study Speciesmentioning

confidence: 99%

Do leucocyte profiles reflect temporal and sexual variation in body condition over the breeding cycle in Southern Rockhopper Penguins?

et al. 2011

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Sexual Dimorphism and use of Morphological Measurements to Sex Adults, Immatures and Chicks of Rockhopper Penguins

Abstract: BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Cited by 43 publications

References 19 publications

Females Paired with New and Heavy Mates Reduce Intra-Clutch Differences in Resource Allocation

Females Paired with New and Heavy Mates Reduce Intra-Clutch Differences in Resource Allocation

Sex-specific foraging behaviour and a field sexing technique for Endangered African penguins

Do leucocyte profiles reflect temporal and sexual variation in body condition over the breeding cycle in Southern Rockhopper Penguins?

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