Morphometric differences between sexes and populations in Norwegian Dunlins Calidris alpina

Abstract

ABSTRACT Capsule The sex of Dunlins from two widely separated Norwegian breeding populations can be determined using morphometrics, with the Dunlins’ sizes differing between populations. Aims We aimed to understand the Dunlin’s physical characteristics within and outside of a zone of intergradation between the subspecies C. a. schinzii and C. a. alpina, and to provide a resource for determining the sexes. Methods We tested for morphometric differences between Dunlins from Finnmark, inland South Norway and coastal South Norway to determine if any or all of these populations had unique characteristics. We also compared morphometrics from our study with those in published sources. We performed discriminant function analyses on morphometric data from Dunlins of known sex to identify variables that could be used for sex identification in captured birds. Results Dunlins from Finnmark were significantly larger than those from South Norway. However, birds from inland South Norway, and a small sample from coastal South Norway, overlapped in multiple measurements. Our comparison with previously published sources also found no clear differences in morphometrics between birds from South Norway and C. a. schinzii from other populations. Our discriminant functions for both Finnmark and inland South Norway accurately predicted the sex of Dunlins using only the wing chord and bill length measurements. Conclusion There was no clear evidence that Dunlins from the subspecies intergradation zone in South Norway differed in size from subspecies C. a. schinzii. The sex of Norwegian-breeding Dunlins can be accurately determined by morphometrics alone, using population-specific discriminant functions.