Silver gull (Larus novaehollandiae)

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Silver gull fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Silver gull description

A small- to medium-sized gull species ⁽⁴⁾, the silver gull (Larus novaehollandiae) has a slim body, narrow wings and a sloping forehead ⁽³⁾. The white colouration of the silver gull’s head, body and tail blends into a delicate grey on the back and wings ^{(2) (4)}. The primary feathers of the silver gull are mostly black, and the tips of the outer three wing feathers are patterned with white spots ⁽²⁾.

The bill is short and slender ⁽³⁾, and like the legs and feet it is bright red ^{(2) (3) (4) (5)}. The silver gull has whitish eyes ^{(2) (5)}, which are surrounded by a red, fleshy ring. Silver gull populations in the east of the species’ range have brighter bare parts than those in the west ⁽²⁾, and non-breeding adults are known to have a slightly duller bill and legs than breeding individuals ⁽³⁾.

Male and female silver gulls are similar in appearance ⁽³⁾, but males usually have a longer bill than females ⁽²⁾.

The juvenile silver gull generally has browner plumage than the adult, with brown mottling on the mantle and wings and brown markings on the head. A dark brown band towards the tip of the tail also distinguishes the juvenile silver gull from the adult ^{(2) (4)}. The bill of the juvenile silver gull is dark ^{(2) (3)}, while the legs vary from a pinkish, fleshy colour to black ^{(2) (4)}. The juvenile silver gull moults into its adult plumage at about 12 months old ⁽²⁾.

The silver gull is described as having a harsh, screaming call, such as ‘korr’ or ‘keow’ ⁽⁴⁾.

Also known as

red-billed gull, sea pigeon.

Synonyms

Chroicocephalus novaehollandiae.

Size

Length: 38 - 43 cm ⁽²⁾

Wingspan: 91 - 96 cm ^{(2) (3)}

Weight

260 - 350 g ⁽²⁾

Silver gull biology

The silver gull is a gregarious bird ^{(3) (4)}, and is often found in large flocks of hundreds to thousands of individuals ⁽³⁾. This species generally roosts at inland sites around the margins of wetlands or floodwaters ⁽³⁾, but it is known to wander widely outside the breeding season ^{(2) (6)}. Seasonal movements have been recorded, with some populations of the silver gull moving short distances from the colony to nearby coastlines. Southern and eastern populations generally migrate northwards, while western populations tend to move southwards ⁽²⁾.

An opportunistic feeder ⁽⁶⁾, the silver gull has an extremely varied diet, including fish, marine and terrestrial invertebrates, seeds, berries, and even bird eggs ^{(2) (3) (6)}, including those of the great crested tern (Sterna bergii) ⁽⁷⁾. The silver gull's foraging habits are as diverse as its diet, and it has been observed 30 kilometres offshore feeding on amphipods at the water’s surface ⁽²⁾, as well as scavenging through human refuse on land ^{(3) (4)}, or feeding on the wing as it hawks after swarming insects ^{(2) (3)}. The silver gull is known to be a kleptoparasite ^{(2) (6) (8)}, stealing food from other species, particularly terns and pelicans ^{(2) (8)}.

The silver gull breeds on small islands ^{(4) (6)}, mainly offshore but also on freshwater or brackish lakes ^{(3) (6)}, and it is known to nest close to tern colonies ⁽²⁾. Although it can occasionally nest in solitary pairs, the silver gull is generally a colonial species ^{(2) (3) (6)}. Colonies in tropical areas tend to be small, usually comprising between 3 and 25 pairs. In the southern parts of its range, silver gull colonies can contain up to 3,000 breeding pairs, although the colony size is limited by the availability of food ^{(2) (6)}.

The timing of breeding in the silver gull varies depending on the location and also on the age of the bird ⁽⁶⁾, with older birds usually nesting earlier and producing more young. In Western Australia, egg laying occurs from March to November, and some pairs may go on to raise a second brood in the same season ⁽²⁾.

The nest of the silver gull is a shallow cup ⁽²⁾, made from grass and other suitable material. It is built in tree stumps or on embankments of wetlands ⁽³⁾, although in the Capricorn Group in the Great Barrier Reef this species tends to nest on sandy or rocky ground with low vegetation. The female silver gull lays a clutch of between one and five eggs, with three being most common ⁽²⁾. The eggs are laid at intervals of two to four days and are incubated by both sexes ⁽³⁾. The incubation period is between 21 and 27 days, and the chicks remain within the colony for a further 4 weeks ⁽²⁾, until the adult birds lead them away ^{(2) (3)}. The young silver gulls gather in small groups, and generally become capable of flight between five and seven weeks of age ⁽³⁾.

Silver gulls are usually able to breed at four years of age ⁽²⁾, although breeding may sometimes occur as early as two years old ⁽³⁾. The silver gull is thought to be able to continue breeding for about 11 years ⁽²⁾. 

Silver gull range

The silver gull has a widespread distribution in Australia and New Zealand ⁽³⁾, occurring along much of the Australian coast ^{(3) (6)}. During the winter, the silver gull expands its range to include the central-northern coast of Australia, as well as inland Tasmania and central, south-western and south-eastern Australia ⁽⁶⁾.

The silver gull is also native to New Caledonia, and is a known vagrant in Fiji, Indonesia, Papua New Guinea and Vanuatu ⁽⁶⁾.

There are currently two recognised subspecies of silver gull. Larus novaehollandiae novaehollandiae is found in southern Australia and Tasmania, while Larus novaehollandiae forsteri is restricted to northern Australia, New Caledonia and the Loyalty Islands ⁽²⁾.

Silver gull habitat

The silver gull can be found in a wide range of habitats, both in coastal zones and inland locations ^{(2) (3) (6)}, including sandy and rocky shores, rubbish dumps, parks and even inland fields ⁽²⁾. At inland locations, the silver gull tends to occur around permanent wetlands, such as lakes, weirs and reservoirs ⁽³⁾, although some birds are known to frequent slaughterhouses and livestock pens ⁽²⁾.

Silver gull status

The silver gull is classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾.

Silver gull threats

The silver gull is not considered to be globally threatened ⁽⁶⁾, and is actually thought to be increasing in abundance. However, it is occasionally treated as a pest at airports and within colonies of other seabird species, and in New Caledonia its current status is unclear ⁽²⁾.

The silver gull is known to nest on the ground in certain parts of its range, particularly in the Capricorn Group of the Great Barrier Reef, and these nests are vulnerable to flooding ⁽²⁾.

Silver gull conservation

The silver gull has a very large range, and is not currently considered to be threatened ⁽⁶⁾. As a result, at present there are no known conservation efforts in place specifically targeting this species.

Find out more

Find out more about the silver gull:

• BirdLife International - Silver gull:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=3236

Learn more about bird conservation in Australia:

• BirdLife Australia:
  http://www.birdlife.org.au/

Find out more about conservation in Australia:

• Australian Wildlife Conservancy:
  http://www.australianwildlife.org/
• Australian Conservation Foundation:
  http://www.acfonline.org.au/

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Glossary

Amphipods

A group of small shrimp-like crustaceans that includes sandhoppers, beach hoppers, and water lice.

Brackish

Slightly salty water, usually a mixture of salt and freshwater, such as that found in estuaries.

Incubate

To keep eggs warm so that development is possible.

Incubation

The act of incubating eggs; that is, keeping them warm so that development is possible.

Invertebrates

Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.

Kleptoparasitism

A feeding method whereby one individual steals food from another.

Mantle

In birds, the wings, shoulder feathers and back, when coloured differently from the rest of the body.

Moult

Periodic shedding of (usually) the outermost body covering (such as feathers, fur or skin) during growth and development, or at specific times of the year.

Primary feathers

The main flight feathers projecting along the outer edge of a bird’s wing.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Vagrant

An individual found outside the normal range of the species.

References

1. IUCN Red List (September, 2012)
   http://www.iucnredlist.org/
2. del Hoyo, J., Elliott, A. and Sargatal, J. (1996) Handbook of the Birds of the World. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.
3. Rogers, K. and Ralph, T.J. (2011) Floodplain Wetland Biota in the Murray-Darling Basin: Water and Habitat Requirements. CSIRO Publishing, Victoria, Australia.
4. Dutson, G. (2012) Birds of Melanesia: Bismarcks, Solomons, Vanuatu, and New Caledonia. A&C Black Publishers, London.
5. Leach, J.A. (2005) An Australian Bird Book: A Complete Guide to the Identification of Australian Birds. Kessinger Publishing, Montana, U.S.
6. BirdLife International (September, 2012)
   http://www.birdlife.org/datazone/speciesfactsheet.php?id=3236
7. Newsome, D., Moore, S.A. and Dowling, R.K. (2002) Natural Area Tourism: Ecology, Impacts, and Management. Channel View Publications, Bristol, UK.
8. Croxall, J.P. (1987) Seabirds: Feeding Ecology and Role in Marine Ecosystems. Cambridge University Press, Cambridge.