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Female Wood Sandpipers Were Larger, but Body Measurements Reliably Sexed Only About 17% of Birds

Wood Sandpiper (Tringa glareola) wading in shallow water
Research · Anatomy & morphology

A 2026 study found that female wood sandpipers (Tringa glareola) were larger than males in all measured linear body traits, but the overlap between the sexes was too great for any single measurement to identify sex reliably.

The researchers measured 168 adult birds caught during spring migration near Turov, Belarus, between 2015 and 2021 and determined their sex molecularly from blood samples. They then tested combinations of external measurements to develop discriminant equations—statistical functions that combine several measurements to estimate sex. The strongest sexual dimorphism was in nalospi length, the distance from the bill tip to the proximal edge of the nostril, followed by bill length; wing, head and leg measurements also differed on average between males and females.

Body measurements were useful but not reliable for every bird

An equation using wing and bill length correctly classified about 73% of birds when every individual was assigned to a sex, with higher success for males than females. When the researchers instead set thresholds intended to keep misclassification near 5% for each sex, accuracy improved for the birds that could be assigned—but about 83% of individuals remained unclassified. A 10% misclassification threshold reduced the unclassified share to 66%.

The authors conclude that the equations can still be useful in large datasets, particularly when researchers need high-confidence sex assignments for a subset of captured birds or want to revisit historical biometric records.

Sources and image credit

  1. Meissner, W., Witkowska, M., Pinchuk, P., & Karlionova, N. (2026). Sexual size dimorphism and sex discrimination in the Wood Sandpiper (Tringa glareola). Birds, 7(1), 8. https://doi.org/10.3390/birds7010008Primary open-access research article published 2 February 2026 under CC BY 4.0. Females were larger than males in all measured linear traits. Discriminant equations based on external measurements classified about 71–73% of all birds when every individual was assigned; thresholds intended to keep sex-specific misclassification near 5% left about 83% of individuals unclassified.

Image: Artemy Voikhansky / Wikimedia Commons — Wood Sandpiper (Tringa glareola) wading in shallow water in Israel, photographed 26 April 2015. Illustrative photograph, not a bird measured in the Belarus study. · CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ · Source

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