Postponed moult of primary coverts untangles the ageing of Wrynecks Jynx torquilla

ABSTRACTIn most bird species, all feathers are moulted at least once per year, usually after breeding (complete post-breeding moult). Woodpeckers (Picidae) often retain some primary coverts and secondaries during their otherwise complete post-breeding moult. To date, this phenomenon has received little attention and has not been studied thoroughly in European woodpeckers, even though it could prove very helpful for ageing and therefore for demographic studies. We studied the moult patterns of breeding adult Wrynecks Jynx torquilla in a Swiss Alpine valley between 2013 and 2016. Due to intensive ringing in the study area prior to the current study, our data set included birds of known age. Some individuals were captured and their moult documented in up to four years in a row. We found that Wrynecks present an extreme case of delayed primary-covert moult. No primary covert (PC) was renewed during the post-juvenile moult. At most three PCs were renewed by the second post-breeding moult and three to six at mo...