Differentiation of subspecies and sexes of Beringian Dunlins using morphometric measures

Abstract

Five subspecies of Dunlins (Calidris alpina) that breed in Beringia are potentially sympatric during the non‐breeding season. Studying their ecology during this period requires techniques to distinguish individuals by subspecies. Our objectives were to determine (1) if five morphometric measures (body mass, culmen, head, tarsus, and wing chord) differed between sexes and among subspecies (C. a. actites, arcticola, kistchinski, pacifica, and sakhalina), and (2) if these differences were sufficient to allow for correct classification of individuals using equations derived from discriminant function analyses. We conducted analyses using morphometric data from 10 Dunlin populations breeding in northern Russia and Alaska, USA. Univariate tests revealed significant differences between sexes in most morphometric traits of all subspecies, and discriminant function equations predicted the sex of individuals with an accuracy of 83–100% for each subspecies. We provide equations to determine sex and subspecies of individuals in mixed subspecies groups, including the (1) Western Alaska group of arcticola and pacifica (known to stage together in western Alaska) and (2) East Asia group of arcticola, actites, kistchinski, and sakhalina (known to winter together in East Asia). Equations that predict the sex of individuals in mixed groups had classification accuracies between 75% and 87%, yielding reliable classification equations. We also provide equations that predict the subspecies of individuals with an accuracy of 22–96% for different mixed subspecies groups. When the sex of individuals can be predetermined, the accuracy of these equations is increased substantially. Investigators are cautioned to consider limitations due to age and feather wear when using these equations during the non‐breeding season. These equations will allow determination of sexual and subspecies segregation in non‐breeding areas, allowing implementation of taxonomic‐specific conservation actions.

Intercontinental genetic structure and gene flow inDunlin (Calidris alpina), a potential vector of avian influenza

“…; Gates et al. ). In these circumstances, hypervariable molecular markers and DNA sequences may be useful for illuminating patterns of population connectivity and movements of individuals throughout the annual cycle (Haig et al.…”

“…; but see Gates et al. ). This is particularly true in eastern Asia where four subspecies are thought to intermix during the nonbreeding season (Lanctot et al.…”

Sexual size dimorphism and sex determination by external measurements in the Redshank Tringa totanus

“…Those from the northern part of the breeding area are smaller than others (Glutz von Blotzheim et al, 1977;Meissner, 1999). As individuals from both groups can be caught during the spring migration in southern Belarus, this may have resulted in lowering the effectiveness of sexing by the discriminant function, as was described in the case of a mixed group of different subspecies of Dunlins (Calidris alpina) (Gates et al, 2013).…”

“…The inclusion of a measurement in the model was based on the Wilk's lambda ratio with minimum partial F to enter the model equal to 3.84, and the maximum partial F to remove from the model was 2.71. Similar to other studies (Sikora and Dubiec, 2007;Ackerman et al, 2008;Gates et al, 2013;Meissner and Krupa, 2016), a priori classification probabilities were set as equal for both sexes (P = 0.50). Despite the presence of a slightly male-biased sex ratio in the sample, we did not adjust the prior probabilities for the analyses, because we did not have prior knowledge of the sex ratio in the population.…”

“…The possibility of identifying the sex of Redshanks could be useful in different studies on ecology, behavior, migration, and conservation of this species, which in Europe has shown a moderate decline in the breeding population between 1980and 2013(EBCC, 2015. However, to limit the misclassification error, individuals with a discriminant score D between -0.96 and 1.17 should be treated as unsexed.…”