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  • Morphological Sex Determination in Black-Faced Cormorants (Phalacrocorax fuscescens)

    Author(s)
    Riordan, Julie
    Johnston, Greg
    Griffith University Author(s)
    Riordan, Julie A.
    Year published
    2013
    Metadata
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    Abstract
    Black-faced Cormorants (Phalacrocorax fuscescens) are endemic to marine environments in southern Australia and little is known of their biology. Development of a reliable and practical method for sexing adult birds in the field is necessary to aid research into their behavior and life-history. Eleven measurements from museum specimens (27 male; 31 female) were used to document sexual dimorphism in Black-faced Cormorants using discriminant function analyses (DFA). A simultaneous DFA correctly sexed 81% of birds, while a stepwise DFA correctly sexed 85% of birds based on two measurements (bill length and mid tail length). ...
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    Black-faced Cormorants (Phalacrocorax fuscescens) are endemic to marine environments in southern Australia and little is known of their biology. Development of a reliable and practical method for sexing adult birds in the field is necessary to aid research into their behavior and life-history. Eleven measurements from museum specimens (27 male; 31 female) were used to document sexual dimorphism in Black-faced Cormorants using discriminant function analyses (DFA). A simultaneous DFA correctly sexed 81% of birds, while a stepwise DFA correctly sexed 85% of birds based on two measurements (bill length and mid tail length). However, terminal wear of the retrices make this measurement unreliable. A logistic regression using bill length correctly predicted the sex of 78% of individuals. Black-faced Cormorants with a bill = 76 mm long are likely female and = 77 mm long are likely male, therefore providing a reliable method for assigning sex in the field. Black-faced Cormorants exhibit the same pattern of sexual dimorphism found in all other cormorants studied to date: males are larger, more robust and have a longer bill compared to the smaller, relatively gracile and shorter-billed females. The use of this general rule to assign sex to adult Black-faced Cormorants was confirmed through the observation of mating behavior. Therefore, this study provides a dependable and practicable technique for assigning sex in the field without the need to capture birds and disturb their behavior.
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    Journal Title
    Waterbirds
    Volume
    36
    Issue
    1
    DOI
    https://doi.org/10.1675/063.036.0114
    Subject
    Zoology not elsewhere classified
    Zoology
    Publication URI
    http://hdl.handle.net/10072/60573
    Collection
    • Journal articles

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