Location: North Island
Coordinates (lat, long): -37.12179 175.25051
Area: 9,000 ha
Date of joining: 1996 March 25
Status: Protected Area
Other listings: Ramsar
Important for Shorebirds
Calidris canutus (Red Knot), Limosa lapponica (Bar-tailed Godwit)
The Firth of Thames Flyway Site (EAAF019) covers an area of 8,500 ha and consists of four main wetland types: shallow estuarine water and mudflats (7,000 ha), grass flats (30 ha), mangrove forest, salt marsh and swamp (730 ha), and shell banks (40 ha). The Firth of Thames supports internationally important populations of both arctic breeding and NZ breeding shorebirds species. It is particularly important for endemic Wrybill Anarhynchus frontalis supporting over 40% of the entire population during the non-breeding season. The Firth of Thames is also the most important wintering site in New Zealand for Black-winged Stilt Himantopus himantopus and third most important site for Pied Oystercatcher Haemantopis finschi. Other significant taxa include Black-billed Gull Larus bulleri, White-fronted Tern Sterna striata and Northern NZ Dotterel (Southern Red-breasted Plover) Charadrius obscurus aquilonius. The intertidal mudflats provide a foraging site for internationally important numbers of migratory shorebirds. It hosts vulnerable species which include Bar-tailed Godwit Limosa lapponica, 4.4% of the flyway population, and Red Knot Caldris canutus, 4.7% of flyway population. A total of 132 species of birds have been recorded in the Firth of Thames, primarily in the environs of Kaiaua – Miranda at the north-western end of the Ramsar site. Of these about 60 species are either abundant or common: the remainder are occasional or rare visitors. The Firth of Thames hosts approximately 35,000 shorebirds each year (mainly along the Miranda coast and the wider Ramsar site extending further to the south and east). Of these about 100,000 are arctic breeders from Siberia and Alaska.
The tidal flats of the Firth of Thames vary from one or two and half kilometres in width at low water on a spring tide and hold an abundance of favoured food items, such as polychaete, worms, shellfish, crabs and shrimps.
Adjoining the Firth of Thames Ramsar site are extensive mangrove forest, salt marsh and pasture. The latter two are used by shorebirds primarily as roosting sites. Along the south-western margin of the Forth is and extensive system of shell ridges or ‘cheniers’. The most recent shell ridge semi-encloses and area of mudflat that is heavily used as both foraging and sub-roosting areas by the main flocks of shorebirds. Inland from the shell ridge is an area of shallow pools (approximately 12 ha) known as the silt pools that are heavily used as a roost site. On the highest tides in the cycle the shell spit and silt pools are the most important roost sites on the entire Firth of Thames.
Threats to the Firth Of Thames:
The major threat to this site is from siltation where sediment is brought unto the tidal area down the existing river systems. These river systems drain a huge area of farm land which gives rise to sediments and nutrients which are carried int o the firth. The increased sediment and nutrient enrichment have a wide range of effects including smothering of the mud dwelling organisms which encouraging the prolific growth of mangroves around the shallow margins. Each of these effects leads to a loss of productivity of the mudflats which could threaten the ability of birds to feed and fatten prior to migration.
There is also a threat of marine farming in the outer regions of the Firth of Thames which could restrict the flow of phytoplankton and zooplankton into the Ramsar site.
The prolific growth of mangroves has also affected the ability of birds to utilise high tide roosts around the margins. the mangroves have enveloped many of the previous roosts making them unusable, which has concentrated the birds into the Miranda area.
The territorial jurisdiction of the site is under the Haruiaki District Council, Waikato District Council and Waikato Regional Council