In most cases, \u201cAtlantic\u201d and \u201cPacific Black Noddies\u201d are uniformly blackish and have a smaller, more crisply demarcated white crown area than Brown Noddy.\u00a0 However, in worn plumage and harsh lighting Black Noddies can appear brown and their crowns can appear more diffuse.\u00a0 Brown Noddy\u2019s crown coloration also varies somewhat with factors that include molt-stage and lighting.\u00a0 When general coloration and crown demarcation are inconclusive, there are potentially more objective differences in overall structure, bill size and shape, and wing contrast.<\/p>

Structure:<\/u>\u00a0 Black is somewhat smaller and more buoyant (tern-like) in flight.\u00a0 Conversely, Brown is bulkier and more gull-like. \u00a0Although the proportions between their wing and tail measurements are similar, Brown\u2019s average about 15% longer and, when seen in flight, its tail feathers often create the impression of being disproportionately long.<\/p>

Bill Size and Shape:<\/u>\u00a0 Black\u2019s bill is appreciably thinner and straighter\u2014or, in other words, Brown\u2019s bill is thicker and more noticeably curved.\u00a0 Black\u2019s bill averages longer while the rest of its head is smaller than Brown\u2019s.\u00a0 In most postures, Black\u2019s eye appears \u201coff-centered\u201d\u2014closer to the back of its head than to the tip of its bill\u2014whereas Brown\u2019s eye is about equidistant from the back of its head and the tip of its bill.<\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t