Silver gull / Larus novaehollandiae / Family - Laridae
Gulls are the best known seabird in the world, and are found from the polar ice caps to the equator. Gulls rarely dive below the surface to feed. With the exception of the kittiwake, they are not oceanic and rarely venture far from land.
Many of the world's 45 gull species nest inland and visit salt water only on migration.
Gulls typically have white under-wings and bodies with square tails. Their upper wings vary from pearl grey to sooty-black. Males and females appear alike in appearance with some species acquiring dark hoods in the breeding season, and bills and legs vary in colour.
Immature gulls differ entirely in appearance from adults, being of a dark streaked and mottled brown, with dark bills and frequently dark bands on the tails. The change to adult plumage may take two to four years.
Gulls are expert fliers. Their flight is buoyant and elegant, circling and hovering over food or turning and twisting sharply.
As a group, gulls are cold water birds with only one species, the silver gull (Larus novaehollandiae), venturing into tropical Australia.
Gulls generally nest in colonies, and occasionally in single pairs. They nest in a variety of sites, such as cliff ledges, or on small projections built up with nest material, on rock stacks, islands, moors, and in some species, in trees.
Gulls usually lay 2 to 3 eggs which may be variable in colour, ranging from creamy to olive or buff, with dark markings. Both parents incubate for 3 to 4 weeks. They remain at or near the nest site. The chicks are fed by both parents on regurgitated food, and are independent in 4 to 6 weeks. Most gull breed annually, however, the silver gull breeds at six-monthly intervals.
Inland gulls are omnivorous, taking fish and aquatic organisms in rivers and lakes, and whatever small life they can find on land, including insects in the air, and worms explosed by ploughing and other farm machines cultivating soil.
Marine gulls feed close to the shore or within a few kilometres of the land. Some follow ships and fishing vessels to pick up refuse thrown overboard.
Great care should be taken when visiting known seabird breeding grounds. Walking or sitting carelessly can destroy eggs or chicks. Some birds are easily frightened and may abandon their eggs and chicks.
Apart from human disturbance, natural pressures such as storms and cyclones also affect seabird numbers. The effects of these natural events can be considerable, but can be tolerated because they are irregular. Unfortunately careless human activity is much more likely to delay or prevent a colony's recovery from natural disasters.
There are many ways we can protect birds and their habitats:
During the breeding season, some islands of the Great Barrier Reef are closed to all visitors. For example, the Brook Islands are completely off limits during summer to protect the thousands of Pied Imperial Pigeons that migrate from Papua New Guinea to nest there.
- Special fire regimes are in place to manage vegetated islands and cays.
- Preservation of the mangrove forests is vital, not only for birds and other animals, but also to maintain the natural tidal flows and to offset the destructive effects of cyclones.
- Pollution control is necessary to protect the Reef from excessive sediment, rubbish and waste that affect critical mangrove, mudflat and inner reef habitats, and alter food supplies.
- Controlling feral animals will help to reduce predation on nesting birds and young.
Control of introduced plants will allow native vegetation to regrow.
- Controlling beach access and vehicles on sand dunes will help to maintain these features and protect vulnerable ground-nesting birds. Dunes are a natural part of beaches and are our first line of defence from coastal erosion due to rising sea levels.