At a feast, he was so impressed with the cooked root of the para fern, that he gave the name Kai-para to the district.

Several large arms extend into the interior of the peninsula at the northeast of the harbour, one of them ending near the town of Maungaturoto, only ten kilometres (6 mi) from the Pacific Ocean coast.

The harbour has extensive catchments feeding five rivers and over a hundred streams, and includes large estuaries formed by the Wairoa, Otamatea, Oruawharo, Tauhoa (Channel) and Kaipara.

[5] The harbour shoreline is convoluted by the entry of many rivers and streams, and is about 800 kilometres (500 mi) long,[6] being the drainage catchment for about 640,000 ha of land.

Big waves from the Tasman Sea break over large sandbanks about five metres below the surface, two to five kilometres from the shore.

Some of this sand is carried into the Kaipara harbour entrance, but mostly cycles out again and then continues moving northwards along the west coast.

[13][14] In Māori mythology, the ocean-going canoe Māhuhu voyaged from Hawaiki to New Zealand and overturned on the northern side of the entrance.

His body was eaten by araara (white trevally), and his descendants to this day will not eat that type of fish.

There are tidal reaches, intertidal mudflats and sandflats, freshwater swamps, maritime rushes, reed beds and coastal scrublands.

Rare species use the harbour for feeding during summer before returning to the Northern Hemisphere to breed, such as the bar-tailed godwit, lesser knot, and turnstone.

Threatened or endangered native species, such as the North Island fernbird, fairy tern, crake, Australasian bittern, banded rail, grey‑faced petrels, banded and NZ dotterels, South Island pied oystercatcher, pied stilt, and wrybill are also present .

Significant local populations of black swan, pūkeko, and grey duck also breed in the area.

[19] Land habitats adjacent to the harbour support some rare botanical species, including native orchids, the king fern, and the endangered kaka beak.

[19] In particular, Papakanui Spit on the south head of the harbour entrance, a mobile sandspit, is important as a breeding and roosting area for the New Zealand dotterel and the fairy tern.

[25] These sub-tribes both descend from the chief Haumoewhārangi who settled on the north end of the Kaipara entrance at Poutō.

[27][28] In 1839, European settlers began arriving in the Kaipara to fell and mill kauri trees and build boats for local requirements.

The stretch of water to Dargaville is broad and straight and provides an easy to navigate route into what were then kauri forests in the interior.

Ships up to 3,000 tons carried timber and logs out along the Wairoa to defy the bar at the harbour entrance before continuing on, usually to another New Zealand port or across the Tasman to Australia.

[29] Further south, Riverhead was an important trading link with the Kaipara and Helensville, and a centre for gum digging.

[32] Coastal sawmill settlements at Tinopai, Arapaoa, Batley, Matakohe, Oneriri, Ōruawharo, Pahi, Paparoa, Tanoa and Whakapirau have become quiet backwaters.

[33] The Kaipara is the largest estuarine harbour on the west coast of New Zealand and provides significant areas of suitable breeding grounds and habitats for juvenile fish.

It has fewer problems with water quality than the Manukau, and is the single most significant wetland for west coast fisheries.

[33] In 2009, NIWA scientists discovered that 98 percent of snapper on the west coast of the North Island were originally juveniles from nurseries in the Kaipara.

The findings show how fragile some fish stocks can be, and highlights the importance of protecting natural habitats, like the Kaipara.

[19][36] In 2002, the Crown settled the historical claims of Te Uri o Hau, a hapū of the northern Kaipara Harbour.

[25][40][41] Currently (2007) about 219,000 cubic metres of sand is mined each year from the entrance and tidal deltas of the Kaipara.

[43][44] In 2008, Crest Energy, a power company, received resource consent to install about 200 underwater tidal turbines in the Kaipara Harbour, which would use the substantial tidal flows moving in and out every day near the harbour mouth to produce electricity for approximately 250,000 homes.

[46] Crest planned to place the turbines at least 30 metres deep along a ten kilometre stretch of the main channel.

[citation needed] As of 2011, the environmental state of the harbour has been called as "nearing crisis" and "in significant decline", with shrinking fish and shellfish stocks, more sedimentation, declining water quality and competition for resource use and development being noted as the main issues, with "ninety-nine per cent of the rivers in the catchment [are] polluted".

A recent pilot survey found that habitats in the estuaries are still extensive, but ninety percent of land cover is no longer indigenous wetland or vegetation.