Saturday, 3 January 2015

Week 65: Black-headed Gull ('Chroicocephalus ridibundus')

The Black-headed Gull was @SpeciesofUK from 16th to 22nd June.

Black-headed gulls are a common species of UK gull, found just as often inland as they are on the coast.[1] They are noisy and quarrelsome birds.

Black-headed Gull
[Wikimedia Commons © Arild Vågen]

Black-headed gulls are members of the Croicocephalus genus.

Gulls are seabirds of the Laridae family. They are closely related to, but distinct from, the tern family Sternidae.[2]

Herring Gull
[Wikimedia Commons © Marek Szczepanek]

Gulls are remarkably cosmopolitan birds. They are found across the globe. In fact, they live on every continent, including the margins of Antarctica.[3]

Most gulls are coastal or inland birds. They don't venture far out to sea (with the notable exception of the kittiwake).[4]

As is the case with many gull species, the black-headed gull was originally placed in the genus Larus.[5]

However, from around 2005, the Larus genus started to be split up. One of the new genera created was Croicocephalus, which now contains several small- to medium-sized gulls including the black-headed gull.[6]

Croicocephalus, appropriately enough for the black-headed gull, means ‘colour’, from Greek ‘chroa’ and ‘head’ (‘cephalus’).[7]

Black-headed Gulls
[Flickr Creative Commons © Jan Stefka]

The black-headed gull's species name Ridibundus means 'laughing', also very appropriate given its noisy cacophony of calls.[8]

The black-headed gull is our commonest inland gull.[9]

The black-headed gull is found commonly almost anywhere inland, so it's not really a 'sea' gull.[10]

The black-headed gull is common across the UK but is most numerous in northern England, Scotland and Wales.[11]

Black-headed Gulls
[Flickr Creative Commons © Stefan Berndtsson]

Most of the world’s black-headed gulls are migratory, breeding in the Palearctic and heading south for the winter. The UK is unusual in that we also have a sizeable resident population.[12]

The UK has about 140,000 breeding pairs of black-headed gulls, which equates to 6% of the total world population. In winter, migrants to the UK swell the number to an incredible 2.2 million birds.[13]

Outside of the UK, black-headed gulls are found in Europe except for the far north, Asia, eastern Canada and in winter also the north and west African and Arabian coasts.[14]

Black-headed Gull
[Wikimedia Commons © Oast House Archive]

There's a good global distribution map for black-headed gulls here.

The black-headed gull is fairly easy to identify.

Gull species have a range of plumages depending on their age and the time of year, making them notoriously tricky to tell apart.[15]

Fortunately, the black-headed gull is relatively easy to pinpoint, especially in its adult summer plumage.[16]

The black-headed gull is a small gull, 39-44cm long with a 94-105cm wingspan.[17]

Black-headed Gull
[Wikimedia Commons © flemming christiansen]

The black-headed gull has a silver grey body with white underparts, black tips on the primary wing feathers, and a distinctive dark red bill and legs.[18]

Black-headed Gull showing Black Wing Tips and Red Bill and Legs
[Wikimedia Commons © ArildV]

In flight, the white leading edge to the wing is a good way of distinguishing the black-headed gull from the common gull.[19]

Black-headed Gulls showing White Leading Edge to Wings
[Wikimedia Commons © Böhringer]

The black-headed gull is best known for its distinctive summer plumage.

The black-headed gull gets its name, rather obviously, from its 'black' (really more a chocolate-brown) head, which is the main feature of its summer plumage.[20]

Black-headed Gull in Summer Plumage
[Wikimedia Commons © Estormiz]

For much of the year though, when in its winter plumage, the black-headed gull loses its black hood and its head is in fact white.[21]

In the black-headed gull’s winter plumage, the only sign of the formerly black head is a small dark smudge to the rear of each eye.[22]

Black-headed Gull in Winter Plumage
[Flickr Creative Commons © Tony Sutton]

Juvenile black-headed gulls have a ginger-brown mantle, shoulders, and wing feathers. They become like the adults over two years.[23]

Immature Black-headed Gull
[Wikimedia Commons © Neil Phillips]

The species most easily confused with black-headed gulls is the Mediterranean gull. However, Mediterranean gulls are very scarce in the UK, only appearing in southern and eastern coastal areas.[24]

Mediterranean gulls are a paler grey than black-headed gulls, lack black wing tips, and have a truly black head that extends from the nape into the neck.[25]

Mediterranean Gull
[Wikimedia Commons © Martin Olsson]

Black-headed gulls are noisy.

Black-headed gulls are sociable and quarrelsome birds and are extremely noisy.[26]

Black-headed Gulls Squabbling
[Flickr Creative Commons © Edwyn Anderton]

Black-headed gulls have a variety of calls. One of the most common is a harsh laugh, which has given it the name ‘laughing gull’.[27]

Black-headed gulls are most often seen in small groups or flocks. They gather in larger numbers when roosting or where there is plenty of food.[28]

Black-headed Gulls
[Wikimedia Commons © Barak Baram]

Black-headed gulls typically eat a variety of worms, insects, small fish and carrion. They'll also take scraps and steal from other birds.[29]

Black-headed Gull with a Fish
[Flickr Creative Commons © Tony Morris]

Black-headed gulls can also be found scavenging for food in household or industrial waste.[30]

The black-headed gull breeds in colonies.

Black-headed gull colonies are formed on cliffs, large reedbeds or marshes, or on islands in lakes, nesting on the ground.[31]

Black-headed Gull Colony in Hampshire
[Flickr Creative Commons © Natural England]

The black-headed gull nest is usually a scrape in the ground or a pile of dead plant material.[32] The eggs are light greenish-blue with dark blotches on them and are smooth and glossy.[33]

Black-headed Gull Nest with Eggs
[Wikimedia Commons © Algirdas]

Both black-headed gull parents share the duty of incubating the eggs.[34]

Black-headed Gull and Chick
[Wikimedia Commons © Gemma Longman]

Thirty-five days after hatching, black-headed gull chicks fledge.[35] Black-headed gulls are fairly long-lived, with a maximum recorded life-span of thirty-two years.[36]

Strange but true…

The black-headed gull is far more common than the ‘common gull’![37]


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