Bouwman, H.Oschadleus, H.D.Barnard, Gustav René2019-12-052019-12-052019https://orcid.org/0000-0002-2327-144Xhttp://hdl.handle.net/10394/33838MSc (Zoology), North-West University, Potchefstroom CampusAre the left and right flight feathers of a bird the same? Are the structures and dimensions the same regardless of individual age, feather age, and sex? Structural flight feather asymmetry has not been explored beyond measurement of feather lengths. Differences in expression of structural asymmetry between feather age, age of the bird, and sex have also been neglected. This study investigated both aspects measuring 12 feather dimensions (illustrated below) of left and right primary 8 (P8) feathers of 248 Southern Masked-Weavers Ploceus velatus. Samples were divided into eight groups to distinguish between feather age, individual age, and sex. The left and right primaries of each group were compared for bilateral symmetry using two-tailed, paired t-tests. Significance was assumed at p < 0.05. Differences were found between left and right primaries, suggesting laterally-associated differences in primary feather structure (LADPFS). The direction and expression of variables differed between groups. For females, I found significant differences in all groups, where the dimensions for Variables 1, 4.1, 4.2, 6.2, and 6.3, indicated structural differences between left and right primaries. For males, I found significant differences in all groups, where the dimensions for Variables 1, 4.1,4.2, 5.1, 5.2, 6.2, 6.4, and 8, indicated structural differences between left and right primaries. As far as I am aware, and after many literature searches, this investigation is the first to show significant structural differences between left and right primaries. I also found differences in direction and expression of feathers between groups and I suggest avenues for further study.enAsymmetryFeathersPrimary feather asymmetryPrimary feather asymmetrySeasonal variationSouthern Masked-WeaversThesis