Söderquist, Pär Norrström, Joanna Elmberg, Johan Guillemain, Matthieu Gunnarsson, Gunnar Measurement of bill length. <p>Bill length was measured (to nearest 0.01 millimeter) along the dorsal side of the maxilla using a caliper. Photograph: Pär Söderquist.</p> bill morphology;Farmed mallards;fitness consequences;hunting purposes;study system;anthropogenic impact;Wild populations;Wild Mallards;mallard population;anthropogenic influence;bill lamellae 2014-12-16
    https://plos.figshare.com/articles/figure/_Measurement_of_bill_length_/1272395
10.1371/journal.pone.0115143.g003