Primary moult in a Northern Lapwing (Vanellus vanellus) population undergoing moult-migration

Abstract

We studied primary moult in a migratory Central European population of the Northern Lapwing (Vanellus vanellus) by collecting shed primaries at a post-breeding concentration site in the riverside meadows of the Vistula River, northern Poland from July to September 2004–2005. In total, 1,270 primaries were used in the analysis. Inner primaries (P1–P7) were identified using mass thresholds established from reference specimens, whereas the three outermost primaries (P8–P10) were distinguished by their white subapical spots and emargination patterns. The mean ordinal number of collected primaries increased progressively from early July to late September, indicating a typical descendant moult primary-moult sequence. However, the wide range of primary ordinal numbers within each sampling period suggests high variability in moult onset, likely linked to differences in laying dates and in the timing of clutch replacement after loss, both within and between breeding populations. High variability of the mean starting dates of primary moult seems to be a characteristic trait of this species regardless of a population’s migratory status. Moreover, two distinct temporal peaks in the proportion of outermost primaries collected indicate turnover of individuals at the site, likely reflecting the departure of early-moulting birds and subsequent arrival of later moulting individuals, possibly representing both inter- and intra-population variation, during September. Post-breeding moult in the Northern Lapwing appears consistent with stopover moult migration, in which birds gather at food-rich sites to complete flight-feather replacement before autumn migration. Our results demonstrate that collecting shed flight feathers can offer a useful, although limited, method for describing moult timing in species that form large post-breeding aggregations and which otherwise may be difficult to capture in sufficient numbers for advanced moult analysis using Underhill–Zucchini and other more comprehensive models, which require data on the growth stages of all neighbouring feathers undergoing moult.