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Exploratory Young Lesser Black-backed Gulls Used Urban Habitats More, but Exploration Did Not Predict Survival

Juvenile lesser black-backed gull in flight
Research · Behaviour

Young lesser black-backed gulls (Larus fuscus) that behaved more exploratively before fledging later used urban habitats more often, while less exploratory individuals relied more on agricultural areas. The study, published on 25 February 2026, was based on birds from the harbour colony at Zeebrugge, Belgium, monitored in 2020 and 2021. The 20-day post-fledging movement dataset included 34 GPS-tagged juveniles; after a further exclusion, the habitat-use models included 30 birds, while the six-month survival analysis included all 51 GPS-tagged juveniles.

The researchers wanted to know whether behavioural differences already visible early in life could predict how inexperienced birds explore their surroundings, choose habitats and survive after fledging. This period is demanding because juveniles must begin finding food and learning the landscape without the experience of adults.

While the gulls were still nestlings, the researchers assessed their exploratory phenotype in a standardised open-field test. After fledging, GPS data from the same birds were used over a 20-day period to measure habitat preferences, spatial movement and revisitation patterns, along with time spent flying, foraging and resting.

Survival was analysed across all 51 GPS-tagged juveniles for six months after fledging, a period that included migration. This allowed the researchers to test whether the early behavioural measure was linked not only to where juveniles went, but also to whether they survived the first months of independent life.

Exploratory birds used cities more

The clearest relationship was with habitat choice. Juveniles that had scored as more exploratory before fledging used urban habitats more frequently after leaving the colony. Birds with less exploratory phenotypes relied more heavily on agricultural habitats.

Early-life exploration did not, however, predict the broader measures of spatial use examined in the study. The researchers therefore found a link with the types of habitats juveniles used, rather than a general tendency for more exploratory birds to range farther or move differently across all spatial measures.

No survival advantage was detected

The six-month survival analysis included 51 juveniles, 29 of which died during the study period. The exploratory phenotype did not predict survival, so more exploratory juveniles were not shown to have either higher or lower survival than less exploratory birds.

The authors discuss several possible reasons for the absence of a survival relationship. Different behavioural types may match themselves to different habitats successfully, random environmental events may outweigh behavioural differences, or the open-field test may not capture the particular aspects of behaviour that matter most for survival.

Sources and image credit

  1. Morel, M., Mitchell, L., Stienen, E., Verbruggen, F., Lens, L., & Müller, W. (2026). Navigating the unknown: how exploratory traits shape juvenile post-fledging behaviour and survival in gulls. Proceedings of the Royal Society B: Biological Sciences, 293(2065), 20252904. https://doi.org/10.1098/rspb.2025.2904Primary peer-reviewed open-access article published 25 February 2026 under CC BY 4.0. The study followed the Zeebrugge harbour colony in Belgium in 2020–2021. Fifty-one juveniles were GPS-tagged; the 20-day movement dataset retained 34, habitat-use models used 30 after a further exclusion, and the six-month survival analysis included all 51 juveniles.

Image: Charles J. Sharp — juvenile lesser black-backed gull (Larus fuscus graellsii) in flight off Sagres, Portugal, photographed 28 October 2022; representative species image, not a bird from the study. Source: Wikimedia Commons. · CC BY-SA 4.0 · Source

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