Sex- and age-dependent breeding plumage acquisition in monomorphic species, the Black-headed Gull Chroicocephalus ridibundus

Abstract In monomorphic species, like in the Black-headed Gull, both sexes look alike breeding plumage. With large sets of data on captured and photographed birds using Underhill–Zucchini moult model, we provided a detailed pattern plumage development this species by age sex. This study, similar to other studies, documented first adults with initial stage head at beginning January, yet mean start date nuptial was end February. Half acquired full about mid-March almost all them before mid-April. The more variable immatures. immatures 19th April, which is 52 days later than adults, majority, i.e., 70%, did not complete until May. We showed for first-time sex-dependent acquisition species. According males started average 7 earlier females their lasted longer. Hence, final completed same sexes. A fully developed hood an important part status signalling during pairing; therefore, completing mating