Black-billed Gull

The black-billed gull, known scientifically as Chroicocephalus bulleri and colloquially as Buller's gull or tarāpuka in Māori, is a gull species endemic to New Zealand. It is a medium-sized bird, typically measuring 35-38 cm in length, with a wingspan of 81-96 cm and weighing around 230 grams. The plumage is predominantly white with silvery grey on the saddle and wings, complemented by black wingtips. Seasonal changes in coloration are noted, particularly around the orbital ring and legs, which vary from black to shades of red throughout the year.

Identification Tips

Distinguished from the similar red-billed gull by its black bill, the black-billed gull has a more delicate appearance, a buoyant and graceful flight, and is generally less noisy. Hybrids between the black-billed and red-billed gulls have been observed, characterized by dark red bills.

Habitat

The black-billed gull is found in a variety of habitats within New Zealand. During the breeding season, it prefers major rivers, especially braided rivers, lakes, and farmland. Outside of breeding, it often frequents estuaries, coastal areas, and urban environments where refuse and scraps are available.

Distribution

This gull is endemic to New Zealand, with a significant portion of the population residing in the Southland region of the South Island. It has also established colonies on the North Island and is occasionally sighted on Stewart Island and The Snares.

Behaviour

Black-billed gulls form colonies around the first nesting pair, with nests often in close proximity. Males may exhibit aggression to defend their territory, though fights are typically brief. Adults roost at breeding colonies or feeding sites, with the latter being more common.

Song & Calls

The black-billed gull has a call similar to that of the red-billed gull, despite being generally less noisy.

Breeding

The gull's breeding behavior includes changes in leg coloration, potentially stimulated by the presence of begging chicks. The species forms densely packed colonies during the breeding season.

Similar Species

The black-billed gull is often mistaken for the red-billed gull but can be differentiated by its black bill and more delicate appearance.

Diet and Feeding

The species is attracted to urban areas and anywhere refuse or scraps are available, indicating a diet that includes human-provided food sources.

Conservation Status

The black-billed gull is currently classified as Near Threatened by the IUCN due to a very rapid decline over three generations. It has been listed as Nationally Critical by the New Zealand Department of Conservation and is considered one of the world's rarest gulls.

Threats

The primary threats to the black-billed gull include predation by introduced mammals and indigenous black-backed gulls, human disturbance, and environmental factors such as flooding and potentially climate change.

Conservation Efforts

Conservation efforts include the control of black-backed gull populations to reduce predation on black-billed gull chicks and other threatened bird species. The species has also been featured in conservation awareness campaigns such as the Bird of the Year competition.