The black-headed gull (Chroicocephalus ridibundus) is a small gull that breeds in much of Europe and Asia. It is migratory, wintering further south and west from its breeding range. Like most gulls, it is an opportunistic feeder and scavenger, taking food items from the surface of water bodies, by wading, diving, and stealing food from other birds. As a result, the black-headed gull has adapted to utilize a wide variety of food sources and has relatively few specialized predators that target it exclusively. However, it does face predation pressure from a range of generalist predators that opportunistically prey on eggs, chicks, and even adults of the black-headed gull during the breeding season. Understanding the key predators of the black-headed gull provides insights into the selective pressures shaping its evolution and behavior.
Main Predators of Eggs and Chicks
The black-headed gull nests in colonies, often in marshy wetlands and along the shores of inland water bodies across its range. Like most colonial waterbirds, the eggs and chicks of the black-headed gull are vulnerable to predators that come across their nesting colonies. Some of the main predators of black-headed gull eggs and chicks include:
Great Black-backed Gulls
The great black-backed gull (Larus marinus) is the largest gull species in the world. It often associates with colonies of smaller gulls, including black-headed gulls, to prey on their eggs and chicks. Its large size and powerful beak allow it to consume multiple eggs or chicks in one feeding attempt. Though the adult black-headed gulls mob and attempt to drive it away, solitary great black-backed gulls can cause significant losses of eggs and chicks in a colony.
Herring Gulls
Like the great black-backed gull, herring gulls (Larus argentatus) are opportunistic predators of eggs and chicks at black-headed gull colonies. Though smaller in size than the great black-backed gull, herring gulls make up for it by hunting in groups. This allows them to overwhelm the nest defense of adult black-headed gulls. They play an important role in regulating populations of black-headed gulls in coastal regions where both species overlap widely.
Lesser Black-backed Gulls
The lesser black-backed gull (Larus fuscus) is smaller than both great black-backed and herring gulls, but is still an opportunistic nest predator of smaller gulls like the black-headed gull. It employs both solitary attacks and group hunting strategies to prey on undefended eggs and chicks. In recent decades, populations of lesser black-backed gulls have increased dramatically, which likely has increased predation pressure on black-headed gulls through much of their shared breeding range.
Carrion Crows
The carrion crow (Corvus corone) is an intelligent, generalist predatory bird that consumes eggs and chicks of black-headed gulls. Crows search methodically through colonies and utilize both individual and cooperative hunting techniques to find unattended nests. Once they locate a nest, crows will consume eggs and chicks or carry them back to their own nests to feed their young. Along with other corvid species like the hooded crow (Corvus cornix), carrion crows can be significant nest predators of black-headed gulls.
Marsh Harriers
The marsh harrier (Circus aeruginosus) is a raptor that frequents reed beds and wetlands. It often nests near or even within colonies of black-headed gulls. Marsh harriers hunt by coursing low over nesting areas in search of unattended eggs and chicks. The bold, direct attacks of marsh harriers can result in panic and chaos in a black-headed gull colony. Though mobbed aggressively by adults, a determined marsh harrier can depredate multiple nests in a single hunting attempt.
In addition to these primary egg and chick predators, the black-headed gull also faces nest predation pressure from opportunistic mammals like red foxes (Vulpes vulpes) and raccoon dogs (Nyctereutes procyonoides) in some parts of its range. Overall, the diversity of nest predators ensures that black-headed gulls must defend their colonies aggressively and have evolved mobbing behaviors to drive potential predators away.
Predators of Adults
While less frequent than predation on undefended eggs and chicks, predation on adult black-headed gulls does occur, especially during the breeding season when the gulls are occupied with nesting activities. Some key predators of adult black-headed gulls include:
Peregrine Falcons
The peregrine falcon (Falco peregrinus) is a swift, agile raptor that preys on medium-sized birds like pigeons and shorebirds. Peregrines occassionally target adult black-headed gulls during the breeding season. Utilizing their characteristically high-speed stoops and powerful talons, peregrines can catch and dispatch even healthy, alert gulls as the flock and fly between nesting and feeding areas. Though gulls make up a small portion of the peregrine’s diet, they opportunistically prey on them when available.
Northern Goshawks
The northern goshawk (Accipiter gentilis) is a forest-dwelling raptor that is sometimes found hunting near black-headed gull colonies bordering woodland areas. With their short, broad wings and fast, agile flight, goshawks are adept at maneuvering through trees and surprise attacking flying prey. Adult black-headed gulls may fall prey to goshawks if they stray too close to the forest edge.
Eurasian Sparrowhawks
Smaller and more nimble than the northern goshawk, the Eurasian sparrowhawk (Accipiter nisus) shares a similar ambush hunting strategy. Its compact size allows it to launch surprise attacks in partially obstructed settings around black-headed gull colonies in small forest groves, hedgerows, and scrub habitat.
Brown Shrikes
Unlike the raptors, the brown shrike (Lanius cristatus) is a perching bird similar in size to the black-headed gull itself. Shrikes are predatory songbirds, sometimes referred to as “butcher birds” for their hunting habits. Brown shrikes will sit motionless on an exposed perch before suddenly attacking flying prey like adult black-headed gulls. While mobbed intensely, shrikes are agile flyers that can catch healthy gulls in mid-air with their hooked talons before dispatching them. They then carry the gulls back to perches to consume.
Though attacks are far less common than on eggs and chicks, predation on adults by falcons, accipiters, and shrikes likely helps select for increased vigilance and anti-predator behaviors in black-headed gull colonies. Predation on incubating adults can also expose their eggs and chicks to subsequent nest predation. So deterring these predators is important for black-headed gull breeding success.
Conclusion
In summary, the black-headed gull faces diverse predation pressure depending on its life stage:
Eggs and chicks are consumed by opportunistic predators like large gulls, corvids, and marsh harriers in the colony itself. Defending nests from these predators is critical.
Adults are preyed on less frequently by falcons, accipiters, and shrikes during foraging and nesting. Remaining vigilant and evading attacks by these predators increases adult survival.
This predation pressure has shaped the black-headed gull’s social breeding behaviors, nest defense strategies, habitat preferences, and antipredator mobbing behaviors. Understanding what preys on this species provides key insights into its ecology and evolution among other colonial waterbirds facing similar pressures. Careful conservation management of critical wetland and coastal nesting habitats can help ensure the black-headed gull continues to thrive across its wide range in Eurasia.
