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Biometric sex discrimination is unreliable when sexual dimorphism varies within and between years: an example in Eurasian Oystercatchers Haematopus ostralegus

van de Pol, Martijn; Oosterbeek, Kees; Rutten, Anne L.; Ens, Bruno J.; Tinbergen, Joost M.; Verhulst, Simon

Description

Molecular sexing of birds has been possible for over a decade, but for practical reasons many studies still use biometric data for sex discrimination. In some species, the sexes are easy to distinguish but sexual dimorphism is often more subtle, requiring the use of statistical analyses of biometric measurements to discriminate sexes. These models are usually parameterized and validated using data from a limited number of sites and years. However, the resulting discriminant functions are often...[Show more]

dc.contributor.authorvan de Pol, Martijn
dc.contributor.authorOosterbeek, Kees
dc.contributor.authorRutten, Anne L.
dc.contributor.authorEns, Bruno J.
dc.contributor.authorTinbergen, Joost M.
dc.contributor.authorVerhulst, Simon
dc.date.accessioned2015-12-10T23:09:07Z
dc.identifier.issn0019-1019
dc.identifier.urihttp://hdl.handle.net/1885/63343
dc.description.abstractMolecular sexing of birds has been possible for over a decade, but for practical reasons many studies still use biometric data for sex discrimination. In some species, the sexes are easy to distinguish but sexual dimorphism is often more subtle, requiring the use of statistical analyses of biometric measurements to discriminate sexes. These models are usually parameterized and validated using data from a limited number of sites and years. However, the resulting discriminant functions are often applied to other populations and periods. A crucial, but usually untested, assumption is that sexual dimorphism does not vary in time and space. Here we illustrate the consequences of violation of this assumption in Eurasian Oystercatchers Haematopus ostralegus, a species for which most studies have relied on biometric sexing. Using biometric data from captures of known-sex birds, we show that sexual dimorphism varied substantially in time and even reversed in some months and years. Furthermore, some biometric traits used in sexing changed gradually over time, causing a reduction in sexual dimorphism. We show that the consequences of this variation on sex discrimination in Oystercatchers are subtle and easily overlooked, but can result in inaccurate and strongly male- or female-biased sex-ratio estimates. We recommend that biometric sexing should be avoided in Oystercatchers unless specific calibration for each month, year and area is carried out. This recommendation also applies to other species where biometric traits may depend on environmental conditions. We argue that this condition might apply to many bird species and therefore advise caution when interpreting results based on biometric sex discrimination.
dc.publisherBritish Ornithologists Union
dc.sourceIbis
dc.subjectKeywords: biometry; calibration; environmental change; feeding ecology; morphology; sex determination; sex ratio; sexual dimorphism; wader; Aves; Haematopodidae; Haematopus ostralegus Bill morphology; Environmental variation; Feeding ecology; Sex ratio bias; Shellfish
dc.titleBiometric sex discrimination is unreliable when sexual dimorphism varies within and between years: an example in Eurasian Oystercatchers Haematopus ostralegus
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume151
dc.date.issued2009
local.identifier.absfor060308 - Life Histories
local.identifier.absfor060201 - Behavioural Ecology
local.identifier.ariespublicationu9511635xPUB794
local.type.statusPublished Version
local.contributor.affiliationvan de Pol, Martijn, College of Medicine, Biology and Environment, ANU
local.contributor.affiliationOosterbeek, Kees, SOVON Dutch Centre for Field Ornithology
local.contributor.affiliationRutten, Anne L., University of Groningen
local.contributor.affiliationEns, Bruno J., SOVON Dutch Centre for Field Ornithology
local.contributor.affiliationTinbergen, Joost M., University of Groningen
local.contributor.affiliationVerhulst, Simon, University of Groningen
local.description.embargo2037-12-31
local.bibliographicCitation.startpage171
local.bibliographicCitation.lastpage180
local.identifier.doi10.1111/j.1474-919X.2008.00891.x
local.identifier.absseo960802 - Coastal and Estuarine Flora, Fauna and Biodiversity
dc.date.updated2016-02-24T12:08:41Z
local.identifier.scopusID2-s2.0-58149086912
local.identifier.thomsonID000261836400015
CollectionsANU Research Publications

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