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Opposite Spring Migration Strategies Were Linked to Breeding Success in Male and Female Dunlins

Dunlin in flight in Vancouver, Canada
Research · Ecology

A tracking study of dunlins (Calidris alpina hudsonia) breeding near Churchill in Manitoba, Canada, found that spring migration strategy was associated with later reproductive performance in different ways for males and females. The researchers used light-level geolocators to reconstruct individual migration routes and compared these with lay dates, egg volume and daily nest survival. These small tags estimate broad geographic position from changing light levels and the timing of sunrise and sunset, so they reconstruct migration routes less precisely than GPS tracking.

Males benefited from shorter, more direct routes

For males, shorter and more direct spring migrations were associated with higher daily nest survival. This pattern was not explained by earlier arrival or earlier nesting: the researchers found no evidence that earlier male arrival was linked to earlier egg-laying at the nest or that arrival timing itself improved reproductive success.

Females showed the opposite pattern

Females showed the opposite pattern. Longer migrations along less direct routes and at lower speeds were associated with larger eggs, and females travelling longer distances along less direct routes also had higher daily nest survival. The authors interpret this as support for a more relaxed migration strategy in females, in which slower or less direct travel may allow birds to reach the breeding grounds in better condition for egg production. Body condition before breeding was not measured, so this mechanism remains a proposed explanation rather than a demonstrated cause.

Neither the number nor length of stopovers, nor the timing of arrival at the breeding grounds, showed a detectable effect on reproductive success. The results therefore suggest that how spring migration was completed mattered differently for males and females, rather than reproductive success simply depending on how early a bird reached the breeding area.

Sources and image credit

  1. Wright, L. L., Nol, E., & McKinnon, L. (2026). Sex-specific carryover effects of long-distance migration strategies in a sub-Arctic nesting shorebird. Animal Behaviour, 239, 123637. https://doi.org/10.1016/j.anbehav.2026.123637Primary research article in the September 2026 volume; the article was publicly available by 14 August 2026, which is used as the earliest independently verifiable public date. Light-level geolocation of Calidris alpina hudsonia breeding near Churchill, Manitoba, showed that shorter, more direct spring migrations were associated with higher daily nest survival in males, while longer, less direct routes were associated with larger eggs and higher daily nest survival in females. Stopover number and duration and breeding-ground arrival timing showed no detectable effect on reproductive success.

Image: Nigel — dunlin (Calidris alpina) in flight in Vancouver, Canada, photographed 24 November 2013; representative species image, not one of the birds tracked in the Churchill study. Source: Wikimedia Commons. · CC BY 2.0 · Source

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