Tha Ton Marsh
Location:	20°02'N, 99°24'E; 3 km southeast of the village of Ban Tha Ton, Mae Ai District, Chiang Mai Province.
Area:	c.6,000 ha.
Altitude:	c.450m.
Biogeographical Province:	4.10.4.
Wetland type:	11, 13, 15 & 18.
Description of site:	A marshy basin lying upstream of the confluence of the Nam Mae Kok and Nam Mae Fang rivers. The rivers are broad with sand and shingle banks at their confluence. Upstream, for about 13 km above the confluence, the Nam Mae Fang is deeper and slower-flowing, fringed with reeds and tall grasses. These riverine marshes form a corridor 0.2-2.0 km wide and occupying a total area of 1,350 ha, but are now much fragmented. There are also small areas of fish ponds. The most extensive lowlands, in the northern part of the basin, are occupied by rice paddies (approximately 4,600 ha). To the south, there are low hills with patches of degraded dry dipterocarp woodland and cultivation. The area is at its wettest during the late wet season from October onwards, into the early dry season, whcn active irrigation of the rice paddies occurs. At this time, the wetland is flooded to a depth of 20-30 cm. It dries out almost completely from February onwards, apart from a small area of irrigated rice paddies. The rivers are permanent, but their water level drops markedly in the late dry season, from March onwards. Small areas of open water remain in the fish ponds.
Climatic conditions:	Tropical monsoonal climate with an average annual rainfall of 1,268 mm (range 500-2,032 mm), 89.1% of which falls during the southwest monsoon in May to October. The mean annual temperature is 25.8°C (range 6.0-41.5°C). (Data from Chiang Mai).
Principal vegetation:	No detailed surveys of aquatic communities have been made, but the vegetation is believed to be poor in species. The dominant emergent is probably Saccharum arundinaceum, with some Phragmites australis. Large areas are now dominated by Mimosa pudica. Adjacent areas are predominantly agricultural land, with rice paddy in the low-lying areas and sugar cane and maize in the foothills, among patches of dry dipterocarp woodland dominated by species of Shorea and Dipterocarpus. The watershed of the Nam Mae Kok still supports some sub-montane and montane evergreen forest and secondary growth.
Land tenure:	The wetland is mainly or entirely in private ownership. Surrounding areas include both privately owned farmland and National Reserve Forest in public ownership.
Conservation measures taken:	None.
Conservation measures proposed:	The Site might be considered for establishment as a Non-Hunting Area or other reserve.
Land use:	Rain-fed rice paddy (one crop per year) on 2,300 ha, and irrigated rice paddy (two crops per year) on a further 2,300 ha. Some fields of maize and vegetables are grown among the drier parts of the reed-beds, and there is grazing by domestic buffalo. Maize and sugar cane are grown as "slash-and-burn" crops in the nearby foothills.
Possible changes in land use:	With greatly improved drainage, the continued annual burning of reed-beds in order to open up new areas for cultivation is a major threat to roosting and nesting sites for birds. Existing estimates of the cover of "natural grassland", which includes reeds, are probably highly inaccurate. The reed-bed is already greatly fragmented and could completely disappear unless it is afforded some protection in the near future. There is also much illegal hunting and netting of birds.
Disturbances and threats:	With greatly improved drainage, the continued annual burning of reed-beds in order to open up new areas for cultivation is a major threat to roosting and nesting sites for birds. Existing estimates of the cover of "natural grassland", which includes reeds, are probably highly inaccurate. The reed-bed is already greatly fragmented and could completely disappear unless it is afforded some protection in the near future. There is also much illegal hunting and netting of birds.
Economic and social values:	No information.
Fauna:	One of the most outstanding areas in northern Thailand in terms of the variety of wintering birds which it supports. Small numbers of herons (Egretta garzetta, E. intermedia, E. alba) winter in the area, and Ardea cinerea and Botaurus stellaris are both annual visitors. There are occasional records of Ciconia nigra, Tadorna ferruginea and Anas poecilorhyncha (up to five birds). During the ploughing stage of the rice paddies (December-January), the basin attracts many hundreds of shorebirds, particularly Charadrius dubius, Tringa glareola and Calidris temminckii). There are also flocks of up to 20 Vanellus cinereus, many wagtails (chiefy Motacilla flava, M. citreola) and pipits (chiefly Anthus cervinus). The Rosy Pipit Anthus rosealus was discovered wintering here in 1982; 15-20 birds are usually present (Round, 1983). A few harriers, Circus (aeruginosus) spilonotus and C. melanoleucos, also winter in the area. The reed-beds provide a roosting site for many hundreds of wagtails and buntings (Emberiza aureola, E. fucata, Melophus lathami). There are recent records of Charadrius placidus on sand banks on the Nam Mae Kok at Tha Ton. There are few breeding season records, but sand banks on the rivers are known to support a few breeding pairs of Charadrius dubius. The marshes probably support a few pairs of Ixobrychus sinensis, I. cinnamomeus and Dendrocygna javanica. The reed-bed is one of very few sites known to support the scarce and local Saxicola jerdoni. At least two territories are known and the species is presumed to breed. The area is a former site for Grus antigone which is now extinct in Thailand. In addition, there are old records of both Esacus magnirosiris and Sterna aurantia from sand banks on the Nam Mae Kok at Tha Ton (Deignan, 1945). Both of these species may still occur in Thailand but are thought to be endangered.
Special floral values:	None known.
Research and facilities:	Most of what is known about the site has been gleaned from the reports of those visiting bird-watchers who have filed their records at the Center for Wildlife Research.
References:	Deignan (1945); Land Use Classification Division (1977-1979); Round (1983).
Criteria for inclusion:	2b.
Source:	Jira Jintanugool and Philip D. Round.