Gulls, often broadly and incorrectly called “sea gulls,” are highly adaptable birds that have successfully colonized a wide range of habitats across the globe. Their nesting locations reflect this flexibility, extending far beyond the typical seaside image to include both remote, natural landscapes and heavily modified urban environments. Nest site selection is primarily driven by two factors: proximity to reliable food sources and safety from predators.
Coastal and Remote Nesting Locations
Gulls traditionally choose remote, undisturbed coastal areas for breeding, prioritizing sites that offer natural protection from land predators. Small, isolated islands and offshore rocks are highly favored as they provide a natural barrier against terrestrial threats. These locations are often characterized by dense, noisy colonies where hundreds or even thousands of pairs nest in close proximity.
Rocky coastlines and steep cliffs also represent a typical nesting habitat, offering ledges that mimic the safety of elevated sites. Species like the Kittiwake build their nests on narrow cliff faces, making them virtually inaccessible to predators. Other gulls are ground-nesters, choosing open spaces like sand dunes, shingle beaches, or expansive salt marshes. In these ground-level habitats, nests are typically placed near shelter, such as a rock or shrub, for windbreak and camouflage.
The selection of these natural sites ensures immediate access to marine food resources, which is crucial for raising their young. Even inland-nesting species, such as Franklin’s Gull, select remote, predator-free environments like shallow freshwater wetlands where they construct nests from floating vegetation. Site fidelity is a common trait, with pairs often returning to the same general area in successive years.
Urban and Inland Nesting Adaptations
Many gull species have demonstrated a remarkable capacity to adapt their nesting behavior to human infrastructure, driven largely by the availability of refuse and discarded food in urban areas. Flat, gravel-covered rooftops on large commercial or industrial buildings have become popular nesting sites. These rooftops closely mimic the elevated, predator-free isolation of natural cliff ledges and offer safety from ground-based predators.
Gulls frequently tuck their nests against low structures on these roofs, such as air conditioning units, pipes, or parapet walls, using them for protection and stability. This adaptation is common among species that traditionally nest on cliffs, such as the Herring Gull and Lesser Black-backed Gull. Other non-traditional sites include industrial structures, harbor docks, and bridge supports, all chosen for their height and inaccessibility.
Furthermore, gulls have established significant inland populations far from any coast, frequently near large freshwater bodies, reservoirs, or agricultural areas. For these populations, the primary draw is the dependable food source found at landfills, agricultural waste sites, or in urban parks and fast-food districts. These inland gulls often spend a significant portion of their time foraging in terrestrial environments, sometimes preferring these sources over marine prey when feeding high-demand chicks.
Nest Structure and Materials
The physical construction of a gull nest is generally simple, reflecting the bird’s ground-nesting origins and opportunistic nature. Most species begin by creating a shallow depression or “scrape” in the substrate, whether it is soil, sand, or gravel. This scrape serves as the central nest cup where the eggs will be laid and incubated.
The nest is then lined and built up using materials collected from the immediate surroundings, varying widely depending on the environment. In natural settings, gulls use materials such as:
- Grasses
- Twigs
- Seaweed
- Feathers
- Pebbles
Nests in salt marshes may be built up higher on a platform of herbaceous matter to protect the eggs from tidal flooding.
In urban and industrial environments, the material palette shifts to reflect human presence. Nests on rooftops may incorporate artificial debris such as plastic pieces, paper scraps, cloth, and discarded rope. The finished nest is usually a rounded mat or saucer shape, with the size ranging from about 7 inches up to over 18 inches in diameter for the largest gulls. Gulls are colonial breeders, and pairs maintain a small territory around the nest, the size of which varies by species.