The feeding ecology, requirements and distribution of Baikal Teal Anas formosa in the Republic of Korea

Abstract

An overwintering population of up to 20, 000 Baikal Teal was found at the Ch'unam reservoirs in the Republic of Korea in 1984. The first detailed studies at the site were undertaken in December 1989 and January 1990; it comprises three water storage reservoirs, Sannam (75 ha), Ch'unsan (307 ha) and Tongp'an (50 ha), located on the south side of the Nakdong river valley, South Kyongsang Province (3518'N, 12814'E), and holds 18-20,000 Teal in large monospecific flocks. Sixty-two percent of the birds were males in full breeding plumage, and 17% were paired. Displaying Teal were noted only twice. Feeding was predominantly nocturnal, the lakes being used as a diurnal roost. All birds formed into one flock at dusk and then flew up to 7 km to feed on agricultural land. Observations and faecal analysis showed that the birds were feeding exclusively on rice from paddy fields which had been harvested by machine in the previous autumn and were completely dry. Seventy three percent of harvested rice fields were suitable for Teal to feed on, the rest being cleared (9%), burnt(7%) or ploughed (11%). Occasional birds fed during the day on the reservoirs by either dabbling or filter feeding in melt water lying on top of the ice after an overnight freeze. Estimates of energy requirements and food intake suggest that the population requires 111,600-225,000 kg of rice ears for a 90 day season (1.8 million bird days) and that therefore 3392-13,636 ha of suitable harvested rice fields are needed to support them throughout the winter or more if other granivores are competing. There are 3478 ha of suitable rice fields within 8 km of the reservoir. The birds are threatened by disturbance from fishermen, hunters, visiting tourists and local domestic traffic. Overhead power cables may cause significant mortality. None of these is a major threat at present but the exclusive, monospecific nature of Baikal Teal makes them vulnerable to particular hunting techniques or chance events such as disease. A survey of 12 other potential sites in the southern part of the Korean peninsular found only three suitable, one of which held 200 Baikal Teal.