SICB 2019: Urban Gulls Alter FID and Flight Behaviors

Urbanization is a global form of habitat change that alters native habits and either excludes the animals that live there or forces them to acclimate to novel environments. Altering behavioral strategies can allow individuals to quickly acclimate and successfully colonize urban habitats, reproduce and live within them. In two studies presented at SICB, researchers, Dr. Stephen Ferguson with Kalamazoo College and Cara Williamson with the University of Bristol, explored how urban gulls are altering their behaviour in response to aspects of urban environments from two very different perspectives.

One of the birds main predator avoidance behavior is to simply fly away. Flight initiation distance (FID) is measured as the distance investigators are able to approach before the bird flees and simulates this avoidance behavior.  The trend of decreased FID in urban habitats has been observed in many taxa and is often attributed to habituation to human presence. Dr. Stephen Ferguson at Kalamazoo College, investigated if groups of silver gulls (Chroicocephalus novaehollandiae) on Penguin Island, Australia, used context cues to vary FID behaviors based on exposure to and predictability of human interactions.

Dr. Ferguson and colleagues measured FID in three groups of gulls: 1) the native habitat and least disturbed areas of the island, 2) the beaches where human contact was common but unpredictable and 3) on the boardwalk where human interaction was common and predictable. They found that boardwalk gulls had the shortest FID compared to the beach and native gulls. The significant difference between beach and boardwalk gulls suggests that urban gulls are using predictable context cues during human interactions to alter FID. This suggests that urban gulls are not simply habituated humans, but can recognize the context of approach and alter behaviors accordingly.

The effects of human perturbation and habitat alteration on existing ecosystems are often the focus of urbanization research. However, the ways animals acclimate to urban environments can also inform human endeavours. This is the focus of a study conducted by PhD student Cara Williamson’s at the Bristol Robotics Lab at the University of Bristol in the United Kingdom. She is investigating how urban Lesser Black-backed Gulls alter flight strategies to save energy while navigating novel urban habitats, and how this may inform the development of small robotic aircraft that may also have to navigate similar dynamic environments.

Lesser Black-backed Gulls (Larus fuscus) spend a significant amount of time in flight during the breeding season, foraging for their young and themselves. Buildings in urban environments provide dynamic areas to fly through. To evaluate the various flight strategies employed by these birds, GPS units with accelerometers were attached to 11 Lesser Black-backed Gulls and their movements between their nesting grounds and foraging sites were monitored during two breeding seasons. Urban birds use two major flying strategies in cities: 1) orographic soaring which uses lift created by human-made obstructions like buildings and 2) thermal strategies, using temperature to create lift. Cara and her colleagues found that urban gulls employ these two flight types to save energy during longer flights and that aspects of the flight dynamics observed could inform the development of flight robotics in cities.

Note: Cover image at top is by Coekon, Wikimedia Commons