Black-headed Gull

The black-headed gull (Chroicocephalus ridibundus) is a small to medium-sized gull found across Eurasia, parts of northern Africa and northeastern America. It has a distinctive dark chocolate-brown head in the breeding season, which gives it its common name. Outside of the breeding season, the head is white with a dark spot behind the eye. Bill and legs are red, with a black tip to the bill outside of the breeding season. It measures about 38-44 cm (15.0-17.3 in) in length with a wingspan of 94-110 cm (37-43 in). This gull is distinguished from other gulls by its combination of a dark brown head, red bill, and red legs, as well as its more delicate appearance and more agile flight style compared to larger gulls. This gull species is known for its loud, laughing call which is often heard at their breeding colonies.

Black-headed gulls are versatile feeders, consuming a wide range of foods, including insects, fish, worms, and small rodents, as well as scavenging on waste. They are commonly found in a variety of wetland habitats, from coastal marshes and estuaries to inland lakes, rivers, and even urban parks and fields, showing a high adaptability to different environments. Their feeding technique is varied, including surface dipping while flying, picking from the ground, and occasionally hunting small prey actively.

The black-headed gull is partially migratory. Birds from the northern parts of their range in Europe and Asia migrate southwards to warmer regions in winter, whereas populations in milder western European climates, including the UK and parts of coastal Europe, tend to be resident year-round. Their migration is not long-distance compared to some other bird species but is significant for population redistribution.

Breeding season for the black-headed gull begins in late March through to May. They nest in colonies, often with other gull species, on the ground in densely vegetated areas near water. The social dynamics within a breeding colony are complex, with birds often engaging in a range of behaviors from cooperative parenting to aggressive interactions over territory and mates. The colonies are also a hub of vocal activity, with calls used not just for communication between parents and chicks but also for navigating the social hierarchy of the colony.

Nests are constructed from grass, twigs, and feathers, by both male and female, and can vary in size. A typical clutch consists of 2-3 eggs, which are incubated for about 22-26 days by both parents. Once hatched, the chicks are semi-precocial, meaning they are covered in down and are mobile but remain dependent on their parents for food and protection. Chicks fledge around 35-40 days after hatching but remain dependent on their parents for several weeks thereafter.

The black-headed gull has a wide distribution and large population size, which means that it is not considered at immediate risk globally and is listed as least concern on the IUCN Red List. In some areas of its range, particularly in northern Europe, the species has seen a steep decline in recent years. This is believed to be because of habitat loss, pollution, diseases, as well as predation by mink and disturbances by humans at nesting sites. In Norway the number of breeding adults has declined with as much as 80% or more over the last 30 years, which has seen the species getting the status of critically endangered on the national red list.