They have long, thin black beaks that are easily distinguished from the shorter and stouter bright red beak of the red-billed gull (although juvenile red-billed gulls have dark beaks that turn red as they age). They are a similar size to red-billed gulls, but have paler wings and a thinner black border on the wingtips.
Breeding sites are mainly the large braided riverbeds of the South Island. There are scattered colonies on the North Island coast, along with braided rivers in the Hawkes Bay and Wairarapa, as well as Lake Rotorua and Lake Taupo.
In winter black-billed gulls are more coastal, so are often seen in estuaries, coastlines, harbours, and coastal parks.
Disturbing protected birds and destroying nests is an offence under the Wildlife Act 1953 and can result in imprisonment and/or a fine of up to $100,000.
Common threats to braided river birds
Risky river breeding
Breeding on a riverbed is a risky business. Many eggs and chicks do not survive. Riverbed birds have adapted to cope with floods and are able to renest if eggs or chicks are lost.
Birds with good nesting sites are more likely to raise chicks successfully. The best nest sites have:
- islands surrounded by a moat of water for protection from predators
- high points which are less flood prone
- little or no vegetation for all round visibility
- a good food supply close at hand
- little or no disturbance.
Swamp harriers/kāhu and black-backed gulls/karoro are natural predators of braided river birds. These avian predators have taken advantage of changes made by humans and their numbers have increased dramatically.
Braided river birds have good camouflage and use distraction to cope with avian predators. Wrybills, oystercatchers and dotterels often pretend to have a broken wing to lead predators away. Terns, gulls and oystercatchers may dive-bomb and call loudly.
However these defences against avian predators are little use against introduced predators such as cats, stoats, ferrets, rats and hedgehogs. These are the main threats.
Ensuring the survival of the birds' natural open habitat is important in combating predation.
Habitat loss and human disturbance
The fragile ecology of the braided river system is being destroyed by the invasion of weeds.
Human activity including land development and recreational activities disturb nesting birds. Birds may abandon their nests if disturbed.
You can help
- Trap pests near breeding colonies
- Never feed gulls any food or scraps – some of our food is harmful to them
Call 0800 DOC HOT (0800 362 468) immediately if you see anyone catching, harming or killing native wildlife.
Help protect our native birds
Visiting parks, beaches, rivers, and lakes
- Check for pests when visiting pest-free islands.
- Leave nesting birds alone.
- Use available access ways to get to the beach.
- Avoid leaving old fishing lines on beaches or in the sea.
- Follow the water care code and local navigation bylaws.
- Do not drive on riverbeds, or keep to formed tracks if you have to.
With your dog
- Only take dogs to areas that allow them, and keep them under control.
- If you come across wildlife put your dog on a lead and lead it away.
- Warn other dog owners at the location.
- Notify DOC if you see wildlife being harassed by people or dogs.
Other ways to help
- Get your dog trained in avian awareness.
- Volunteer to control predators and restore bird habitats.
- Set predator traps on your property.
- Keep your cat in at night.
- Learn about the Lead the Way programme which encourages dog owners to become wildlife wise and know how to act to protect coastal wildlife.