Changes in Mallard Anas platyrhynchos bill morphology after 30 years of supplemental stocking

Jocelyn Champagnon, Matthieu Guillemain, Johan Elmberg, Karin Folkesson, Michel Gauthier-Clerc

    Research output: Contribution to journalArticlepeer-review

    29 Citations (Scopus)


    Capsule Massive releases of captive-reared Mallard for hunting purposes have been practiced for 30 years. During this period the number of lamellae per centimetre of bill length in wild Mallard populations has decreased. Aims Every year since the 1970s, several million captive Mallard have been released in Europe. This may lead to a spread of unnatural phenotypes into the wild. Nevertheless, the consequences of such introductions have not been examined. Methods Two widespread and common migratory ducks were studied: Mallard Anas platyrhynchos and Teal A. crecca. Mallard is the only duck species for which stocking programmes occur, and Teal served as a control. In a 'before-after' design, we compared duck bill lamellar density over the last 30 years. Results Lamellar density in Mallard, but not Teal, decreased. The observed 10% decrease occurred in the first (proximate) centimetre of the bill, the most crucial in terms of food filtration. Conclusions We hypothesize that the change in bill morphology was because of the propagation of captive Mallard into the wild: captive Mallard eat mainly large items, relaxing the natural selection pressure maintaining high lamellar density for sieving small prey in wild ducks.

    Original languageEnglish
    Pages (from-to)344-351
    Number of pages7
    JournalBird Study
    Issue number3
    Publication statusPublished - 2010

    Swedish Standard Keywords

    • Biological Sciences (106)


    • anseriformes
    • atlantic salmon
    • body
    • dabbling ducks
    • ecomorphology
    • evolution
    • lamellar density
    • length
    • life-history
    • size
    • wild


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