Structural characteristics of important daily movement corridors for waterbirds in urban areas: a field test focusing on Black-headed Gulls
Year: 2026
Type: preprint
Abstract: 1. Many global cities have developed along rivers, subjecting riverine ecosystems to extensive channelization. Straightened rivers have typically been considered too modified to be suitable for aquatic organisms and thus have lacked conservation priority. But considering avian movement decision, such as distance savings and obstacle avoidance, straightened river channels may function as critical movement corridors. Consequently, re-evaluating the ecological value of channelized rivers based on movement ecology can benefit urban waterbird conservation. 2. We tracked the daily movement behaviors of the Black-headed Gull ( Chroicocephalus ridibundus ), a river-dependent waterbird distributed across the Palearctic, and identified key movement corridors in highly urbanized Tokyo, Japan. We collected GPS tracking data for three years from 35 individual gulls within three regions of central Tokyo and additionally measured variables that likely affect bird navigation: river sinuosity and urban feature height (i.e., buildings). We then used generalized linear mixed models to determine relationships between these variables with distances to river centerline (representing fidelity to the river during navigation) across various temporal scales reflecting different individual decision times. Additionally, we predicted and mapped these distances to river centerline across individual river channels in central Tokyo to identify important movement corridors. 3. River structure and feature heights influenced individual river fidelity, but this depended on the spatial and temporal scale of decision-making. Higher feature heights promoted river fidelity during movements based on sudden and mid-term decisions, but not long-term decisions. Conversely, under the broadest perceptual range and for long-term decisions, channel straightness significantly enhanced river fidelity. Overall, results showed that straight river channels with high feature heights represent crucial movement corridors for gulls. 4. Our model identified a key corridor in central Tokyo for waterbird movement that serves to connect daytime habitats to roosting sites. This predictive tendency was also highly robust across all time scales. 5. While straightened river channels with high feature heights may provide unsuitable habitats for some taxa, our results demonstrate their ecological value and importance for conservation as essential movement corridors for waterbirds.
Authors: Shiori Takeshige, Yusuke Sawa, Kazuhiro Katoh
Language: English
Topic: Avian ecology and behavior
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7207528082