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GPS-Based Models Highlighted the Lower Sumida as a Key Black-headed Gull Corridor in Tokyo

Black-headed gull flying in Tokyo, Japan
Research · Ecology

A preprint based on GPS tracking of black-headed gulls (Chroicocephalus ridibundus) in highly urbanised Tokyo showed that the birds followed different river features depending on the scale of their movement decisions. The researchers tested how river sinuosity and the height of surrounding features influenced the tendency to keep following waterways.

During short to medium-term movement decisions, gulls were more likely to follow river sections bordered by taller features. Over longer-term decisions, they were more likely to use straighter channels. The exact results varied somewhat with the distance over which birds were assumed to perceive the landscape, but the overall pattern remained consistent.

When the relationships were mapped across central Tokyo, the models repeatedly identified the lower reaches of the Sumida River as an important movement corridor. This prediction was robust across the different time scales considered.

The authors argue that urban river sections can therefore have ecological value as movement corridors even when their physical structure is poor habitat for many other species. For black-headed gulls, both channel shape and the surrounding urban landscape appear to influence daily movement through the city.

Sources and image credit

  1. Takeshige, S., Sawa, Y., & Katoh, K. (2026). Structural characteristics of important daily movement corridors for waterbirds in urban areas: A case study on Black-headed Gulls [Preprint].Primary preprint posted 3 September 2026. GPS data from black-headed gulls in highly urbanised Tokyo were used to test how river sinuosity and surrounding feature height affected river-following behaviour across movement scales. Short- to mid-term movements were associated with taller surrounding features, long-term decisions with straighter channels, and models robustly identified the lower Sumida River as an important corridor.

Image: Juvenile black-headed gull in flight at Mizumoto Park, Tokyo, Japan, 5 December 2010. Photo: Takashi Hososhima / Wikimedia Commons / Flickr. CC BY-SA 2.0. Representative Tokyo image; not a study bird. · CC BY-SA 2.0 · Source

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