Abstract
We studied on the wintering ecology of Motacilla alba lugens, one of the subspesies of the white wagtail, in the area of about 6 ha, situated at the middle stream of the Tama River, Tokyo, during the periods of November 1972 to March 1973 and October 1973 to March 1974.
Winter territories and undefended feeding ranges were established till November and were maintained through winter. Those territories were occupied by one or two birds, consisting of both sexes. Sexes were checked by their behaviors such as "wing-quivering display" and "vertical flight display". Wanderers without territories tried to intrude in singles. Territorial behaviors against intruders were classified into five patterns; confronting, threat, chase, fight and alert. Territorial birds in the area hold one or more feeding sites out of their territories.
Observation-area curves of territorial birds were classified into three patterns; sigmoid curve, cubic curve and straight line. Those occurrence frequencies changed seasonally and annually. And the size of feeding sites also changed seasonally and annually. Those changes were seemingly unrelated to the rates of territory fixing and to the sizes of territories. However, in every case, the activities of the birds clearly concentrated in feeding sites. Average territory size was 3364m2 in the first winter and 4519m2 in the next winter.
The occurrences of roosting flights concentrated 30 minutes before and after sunset. Most of the birds flew north.
In winter, white wagtail was seemingly dominant in Motacilidae, at least in the study area. Attacks against the predators were also observed.
