Study On Habitat Selection Of White-Eared Night Heron (Gorsachius Magnificus)

The White-eared Night Heron Gorsachius magnificus is one of the endangered species in the world. In south Guangxi, it is distributing in Shangsi County, Fusui County, Hengxian County and Shanglin County. From July 2003 to January 2005, the nest site selection in breeding period, the activity area in non-breeding period, the feeding place and the waterbird community were studied.Three nest-sites were recorded during the survey. Combined with the data from Shennongjia in Hubei Province (one nest-site), all the factors that reflect the nest-site habitat were analyzed by the method of principal component analysis. In breeding period, the habitat with the combination of some factors, including certain elevation, slope, tree and nest height, near water resource, has higher fitness to the bird's nest-site selection. Other key index, such as tree cover and breast-high diameter, also have higher ration of contribution to the nest site selection of the bird. This indicated that the quality and shelter of habitat were the most important factors when selected nest-site. Most of slope of the nest-site was west.In non-breeding period, the elevation between 110~210 meters, the slope between 20~30°, the aspect between southeast to southwest were frequently used by the White-eared Night Heron. As long as certain tree cover met, the forest would be selected as activity place or for whistle stop. It can be evergreen broadleaved forest, evergreen and deciduous broadleaf mixed forest, coniferous and broadleaved mixed forest or coniferous forest. Though the bird did not strict to the type of forest, it preferred to the habitat with high trees and large breast-high diameter. It might relate to theinhabitability and shelter condition.White-eared Night Heron mainly fed on the wetland where there has fish, shrimps, and other aquatic animals. The feeding place can be reservoir, pond, paddy field, stream or ditch. The using of feeding place was analyzed by the method of ANOVA. The results showed that there have not significant differences in the use of different habitat. But there has seasonal difference in the pond usage(F=11.795, P<0.01, df=9). It might relate to food availability between breeding season and winter.In the distribution area of White-eared Night Heron, 32 waterbird species belonging to 5 orders and 6 families were counted. Among these, 5 species were residents, 10 species were summer breeders, 15 species were winter migrants and 2 species were travelers. Their feeding niche was analyzed by using agglomerative clustering method. The results showed that the competition to the heron came from the group sharing shallow water area. The group had 11 diurnal waterbird species and 3 nocturnal waterbird species. White-eared Night Heron was nocturnal species and was ecological isolation from most diurnal waterbirds in the time usage. The feeding sites usage and activity time of Black-crowned Night Heron Nycticorax nycticorax overlapped with those of White-eared Night Heron. It might result in important ecological influence on the latter. The study also indicated winter and early spring were suitable seasons for the survey of the distribution and quantity of White-eared Night Heron.The article also concluded some threats that existed in the distribution area of the bird. It suggested that it was necessary for the conservation of White-eared Night Heron habitat to protect both vegetable structures, shelter condition and food abundance.