Human food sources shape routine movements across elevational gradients in an alpine bird

Human activities are reshaping animal movement patterns worldwide, with human food sources emerging as a significant driver. While such subsidies are known to reduce space use and alter migration behaviour, their role in shaping routine movement patterns-such as sequential visits to specific sites-remains poorly understood.

Here, we investigated the impact of human food sources on the movement patterns of Alpine choughs (Pyrrhocorax graculus), a high-elevation corvid that readily exploits human food. In winter, these birds engage in altitudinal movements, descending from alpine areas to lower elevations in search of food. Thereby, they encounter diverse human food sources ranging from mountain restaurants at high altitudes to urban garbage dumps and bird feeders in the valleys. We analysed the movements of 40 GPS-tagged individuals and combined tracking data with behavioural observations to (1) quantify the occurrence and spatiotemporal patterns of altitudinal movements (2), assess the extent to which human food sources shape space use, and (3) identify potential recursive movement patterns.

Alpine choughs performed daily altitudinal movements during winter, spanning up to 3000 m in elevation per round trip. Birds typically descended in the early morning and returned upslope around midday. Their movements consistently overlapped with human-modified environments providing human food sources, including towns, villages, and mountain restaurants. Notably, individuals repeatedly visited four main foraging locations associated with human food, showing strong route fidelity by returning to the same food-provisioning sites in a consistent sequence and at predictable times of day.

Our findings highlight how human food sources can shape population-level movement patterns and foraging routines, with potential ecological consequences for species increasingly reliant on human-modified habitats. Such dependence may limit behavioural flexibility and create ecological traps, where individuals repeatedly exploit risky or suboptimal resources. By moving daily between alpine and urban areas, Alpine choughs may also transport seeds, nutrients, and pathogens across ecosystems, generating cascading effects in both mountain and lowland habitats.