Great black gulls are a species of large gull found in New Zealand and surrounding islands. They are highly adaptable birds that can be found living in a variety of habitats from coastal areas to inland environments.
Quick Facts
Here are some quick facts about great black gulls:
- Scientific name: Larus dominicanus
- Other common names: kelp gull, karoro
- Size: 61–66 cm (24–26 in) long with 147–170 cm (58–67 in) wingspan
- Weight: 1.1–1.7 kg (2.4–3.7 lb)
- Lifespan: Up to 25 years
- Conservation status: Least Concern
Range and Distribution
Great black gulls are endemic to New Zealand and nearby islands. Their breeding range includes:
- North Island, South Island, Stewart Island/Rakiura of New Zealand
- Chatham Islands
- Solander Islands
- Snares Islands
- Bounty Islands
- Antipodes Islands
- Auckland Islands
- Campbell Island
During the nonbreeding season, great black gulls may disperse more widely across the southwest Pacific. However, most remain relatively sedentary and stay near breeding sites year-round.
Coastal Habitats
Coastal areas provide prime habitat for great black gulls. They thrive along rocky shorelines, sandy beaches, estuaries, harbors, and offshore islands. Typical coastal habitats include:
- Rocky intertidal zones – Foraging on invertebrates and small fish in tide pools and along the shoreline
- Sandy beaches – Feeding on marine organisms washed up by waves
- Estuaries and harbors – Taking advantage of fishery discards and waste from human activity
- Offshore islands – Nesting and roosting on predator-free islands and islets
- Coastal wetlands – Hunting amphibians and small vertebrates at estuaries or lagoons
Access to the ocean provides great black gulls with reliable food sources such as fish, crabs, shellfish, and other intertidal species. Their coastal distribution centers around availability of prey.
Beach Foraging
Beaches provide opportunistic feeding for great black gulls. They scavenge along the high tide line picking at marine animals and other organic matter that washes up. Common beach foods include:
- Dead fish
- Squid, octopus, and other cephalopods
- Marine worms
- Crustaceans such as crabs and shrimp
- Seabird eggs and chicks
- Carrion from marine mammals and seabirds
- Human food waste and litter
Beach foraging is a key feeding strategy for great black gulls, supplemented by other coastal and inland habitats.
Harbor Scavenging
Harbors provide a concentrated food source for opportunistic gulls. Great black gulls frequently scavenge for food around wharfs, fishing vessels, processing plants, and commercial operations. Typical harbor foods include:
- Fishery discards like damaged fish and offal
- Bait such as anchovies from recreational fishing
- Scraps from fish cleaning and processing
- Edible waste from restaurants and markets
- Garbage from trash bins and dumps
Access to plentiful human food waste allows great black gulls to thrive around coastal settlements. Their numbers tend to correlate with commercial fishing activity and urbanization in harbor towns.
Inland Habitats
While centered on the coast, great black gulls also utilize a variety of inland habitats when breeding, roosting, and foraging. Inland environments frequented by great black gulls include:
- Lakes and rivers – Feeding on fish, aquatic invertebrates and amphibians
- Wetlands – Hunting small vertebrates in swamps and marshes
- Pastureland – Foraging on large insect species in open fields
- Rubbish dumps – Scavenging edible waste from landfills
- Urban areas – Exploiting food scraps from human activity
During the breeding season, inland freshwater habitats become particularly important for finding food to provision chicks.
Lake and River Foraging
The freshwater ecosystems of lakes and rivers provide seasonal feeding habitat. Great black gulls forage in shallow waters preying on:
- Small fish species like bullies, smelt, and inanga
- Aquatic invertebrates like snails, shrimp, and insect larvae
- Amphibians such as frogs and tadpoles
- Reptiles including skinks and turtles
Rivers and lake edges also accumulate dead organisms and debris that gulls scavenge. Breeding gulls rely on freshwater food sources that are close to nesting colonies.
Wetland Foraging
Freshwater wetlands like swamps, springs, and marshes offer seasonal feeding habitat. Great black gulls stalk through shallow wetland pools hunting for:
- Amphibians like frogs and salamanders
- Reptiles such as skinks and geckos
- Small mammals including rodents and weasels
- Large wetland insects
- Eggs and chicks of other waterbirds
Wetland foraging provides essential food for breeding gulls and their chicks. It occurs more frequently during wet periods.
Breeding Habitat
Great black gulls return to established breeding colonies each year, typically starting in August. Their nesting habitat preferences include:
- Offshore islands and islets
- Undisturbed sandy beaches
- Spits and dune habitats
- Coastal wetlands
- Riverbeds and lakeshores
- Alpine gravel riverbeds
Breeding sites are chosen for protection from predators. Ground-nesting colonies can contain up to several thousand pairs.
Offshore Islands
Offshore islands provide the safest breeding sites, sheltered from mammalian predators. Preferred islands have:
- Rocky shorelines
- Low vegetation like tussock grass
- Sandy beaches and dunes
- Minimal human disturbance
Seabird colonies on offshore islands can number in the tens of thousands. Great black gulls nest alongside species like penguins, albatross, and terns.
Beach Habitats
Sandy beaches and dunes are also important nesting habitat. Great black gulls colonize beaches that offer:
- Isolation from predators
- Unobstructed access for takeoffs and landings
- Driftwood, debris, and vegetation for shelter
- Good visibility of surrounding threats
Beach nesting is riskier than island colonies due to potential mammal and human disturbance. Solitary nesting or small groups are more common than dense aggregations.
Wetlands
Coastal wetlands provide alternative nesting sites in areas like estuaries, lagoons, and river deltas. Nests are built on:
- Islands in wetland lakes and streams
- Elevated wetland vegetation
- Driftwood snags and logs
The inaccessibility of wetland islands deters predators. Waterlogged terrain also inhibits terrestrial mammals from traversing nesting areas.
Urban Environments
Great black gulls are highly adaptable and often utilize urban habitats. They are common in city areas, particularly around:
- Landfills and rubbish dumps
- Commercial fishing wharfs and processing plants
- Schools, parks, and sports ovals
- Shopping centers, fast food outlets, and restaurants
- Roads and parking lots
Access to predictable, abundant food waste allows urban gull populations to thrive. Their numbers in cities are higher than in natural settings.
Landfill Foraging
Landfills and rubbish dumps provide a prey-rich environment for opportunistic gulls. They scavenge on edible waste including:
- Household food scraps
- Rotting fruit and vegetable matter
- Meat, fish, and bone
- Pet food
Landfill feeding allows gulls to save energy compared to active hunting. They can efficiently gain calories from human garbage.
Urban Scavenging
Great black gulls thrive around human activity in urban areas. They exploit food sources such as:
- Discarded takeaway food
- Cafeteria and restaurant scraps
- Waste from food processing and markets
- Handouts in public spaces
- Roadkill carrion
Scavenging allows gulls to survive at high densities. They are often considered pests in urban environments due to aggressive food stealing.
Habitat Threats and Conservation
Several threats may impact great black gull habitat and populations. Conservation concerns include:
- Introduced mammalian predators
- Human disturbance of nesting colonies
- Pollution and marine debris
- Coastal development
- Climate change
However, the great black gull remains common and widespread. Targeted conservation efforts safeguard key breeding sites.
Introduced Predators
Non-native predators like rats, stoats, possums, and feral cats threaten breeding colonies. They disturb nesting habitat and prey on eggs and chicks. Impacts include:
- Reduced reproductive success
- Abandonment of traditional nesting sites
- Declines in island seabird populations
Eradication and control of invasive mammals on seabird islands is a conservation priority. Biosecurity measures also prevent reinvasion.
Breeding Disturbance
Human interference at breeding colonies can lower reproductive rates. Disturbance activities include:
- Guano harvesting
- Fishing and shellfish gathering
- Recreational access
- Egg collecting
- Industrial activity
Restricting human access helps minimize impacts during the critical nesting and chick-rearing period.
Coastal Habitat Loss
Development along coastlines threatens great black gull habitat. Issues such as:
- Port expansions
- Housing construction
- Tourism infrastructure
- Aquaculture
Can encroach on isolated breeding sites and displace populations. Protecting coastal buffers around colonies is important.
Conclusion
In summary, great black gulls occupy a wide range of coastal and inland habitats in New Zealand and outlying islands. Their distribution centers on the ocean, but also extends significantly inland during breeding season. Conserving the remote islands, beaches, and wetlands required for nesting is key to maintaining populations of this adaptable gull species. Ongoing management of invasive predators and human disturbance threats is necessary to ensure habitat integrity. With proper protection in place, the resilient great black gull will continue thriving throughout its native island range.