20 山 階鳥 研 報 第9巻 第1号(No.48) Wintering ecology of White Wagtail Motacilla alba lugens in the middle stream of Tama River Michihito WATANABE* and Naoki MARUYAMA** White wagtail (Motacilla alba LINNAEUS) widely distributed in Palaearctic, is subdivided into more than ten subspecies. Although, of such subspecies, M. alba alba and M. a. yarreillii, both European subspecies, have been ecologically and ethologicaly studied (GOODWIN 1950, GREAVES 1941, HARTLEY 1946, WHITE 1950, RENDAHL 1967 and ZAHAVI 1971a & b), few deal with Motacilla alba lugens which breeds from South Kamchatka to North Honshu of Japan, and which winters in South Honshu, Formosa, and South China. Accord- ingly, the ecological study on this subspecies may contribute towards the analysis of life-mode of this species. We intend to report on the wintering ecology of this subspecies, Motacilla alba lugens, in the middle stream of Tama River, flowing south of Kanto district. Study Area The study area was situated at the upper stream side of the railroad bridge of National Chuo Line in the middle stream of Tama River, flowing south of Kanto district from Kanto Mountains to Tokyo Bay (Fig. 1). In most of the riverside, submerged riverside grassland, mainly consisting of Miscanthus sinensis and M. sacchariflourus, dominated. Through this grassland, a drainage flows northerly from a sewage to Tama River. On the shore of this dirty and stagnated sewage drainage, muddy and gravel grounds were scattered here and there and provided feeding sites of white wagtail (Fig. 2). On the other hand, Zanbori River, a branch of Tama River, flows about 700m north of the sewage drainage. Concrete bank protection and crowded houses near the stream prevented growth of grass on this riverside. Observations were carried out in the area of about 6 ha along the sewage drainage and in a part of Zanbori River. Methods and Periods White wagtail were observed from the six vantage points for observation, A～F, estab- lished along the sewage drainage from dawn till dusk. In such observations, telescopes (×25, ×40) and binocular (×8) were used. Their behaviors and moving traces were recorded into * Fuji-gakuen High School , Fujiyoshida City, Yamanashi Prefecture ** Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo (20) 昭 和52年(1977)3月 Wintering ecology of White Wagtail 21 Fig. 1. Study area. Fig. 2. Distribution of vegetation, muddy ground and grave ground in the study area. Alphabets in figure represent the locations of the van- tage points, used in observation. (21) 22 山 階 鳥 研 報 第9巻 第1号(No.48) the maps of 1:1,000. It was possible to distinguish between individuals of white wagtail by their various shaped, black breast-plumages, at least in a observation day. This individual distinction method was carried out from January 20, 1973. Furthermore, by their plumage colorations, they were classified into three plumage pat- terns as I, II and III (Fig. 3). The coloration pattern I represents individuals with the black head and the black back. The pattern II represents individuals with the black head and the gray back. The pattern III represents individuals with the gray head and the gray back. The intermediate patterns between such three patterns were also observed and were distinguished as "I-II" and "II-III". In observations, territories were distinguished and called by observation dates and those locations, respec- tively. For example, "territory 3JA" represents a territory observed from the vantage point A on January 20, 1973, and "territory 4MC" represents a territory observed from the vantage point C on March 20, 1974. Observations in the main area, the sewage drainage, were carried out seven times as follows: November 11, December 2, 1972, January 20, March 6, October 9, December 28, 1973, and March 20, 1974. In the sub- Fig. 3. Three plumage colorations area, Zanbori River, observations were carried out as of white wagtail. follows: March 6 and December 28, 1973. Results and Discussion Territory establishment Fig. 4 indicates moving traces of white wagtail on October 9, 1973, immeadiately after the arrival of the birds in Tama River. In usual year, the first birds arrive in early October. Most of the birds conspicuously flew about long distance in single in the area and took food on muddy and gravel grounds along the drainage and around stones scattered on water. Furthermore, we observed little site-attachment and few aggressive behaviors among the birds. While, a few pairs of the birds tried attachment to a certain area including the feeding sites. However, those areas could not be considered as territories. As a result, on this day, it was difficult for us to recognize territory establishment of white wagtail in the study area. On November 11, 1972, about a month after from the first arrival of the birds, white (22) 昭 和52年(1977)3月 Wintering ecology of White Wagtail 23 Fig. 4. Moving traces of white wagtail on October 9, 1973. Hatching represents the feeding sites of white wagtail. wagtail behavior was different from the one in the last month. Most of the birds showed intensive attachment in single or pair to the fixed areas including more than two feeding sites. Those fixed areas were slightly overlapped one another and were considered as either territories or undefended feeding ranges. Fig. 5 indicates territories obserbed from this day till the start of spring migration. Numbers of territories were from 6 to 8, and the territory sites were also stable through a wintering season. It was impossible to convince that the same birds lasted to occupy the same territories through the wintering season. According to the above, territories and undefended feeding ranges of the birds were probably established till November. Territory and territorial behaviors Fig. 6 indicates the points where territorial birds attacked intruders. This repulsive behavior was one of the territorial behaviors, by which the territorial birds drove away intruders out of the areas. Accordingly, such defended areas could be exactly called territories. Those territorial behaviors were classified into the following five patterns. Confronting-Two birds occasionally confronted each other at a distance of 20-30cm near (23) 24 山 階 鳥 研 報 第9巻 第1号(No.48) Fig. 5-a (24) 昭 和52年(1977)3月 Wintering ecology of White Wagtail 25 Fig. 5-b Fig. 5. Locations of white wagtail territories observed in the wintering periods, 1972-1973 and 1973-1974. A. Nov. 11, 1972 B. Dec. 2, 1972 C. Jan. 20, 1973 D. Mar. 6, 1973 E. Dec. 28, 1973 F. Mar. 20, 1974 A and a part of B was described in moving traces and others were described in activity loci. (25) 26 山 階 鳥 研 報 第9巻 第1号(No.48) Fig. 6. Points where territorial birds attacked intruders, on December 2, 1972 and January 20, 1973. Enclosed lines represent the borders of territories. △Fight ▲Chase □Confronting ■Threat ●Alert →Moving traces of dominants →Moving traces of intruders (26) 昭 和52年(1977)3月 Wintering ecology of White Wagtail 27 Fig. 7. Confronting posture of white wagtail. Fig. 9. Fighting postures of white wagtail. Fig. 10. Wing quivering display Fig. 8. a-d Threat postures of white wagtail. of white wagtail. Fig. 11. Vertical flight display of white wagtail. (27) 28 山 階 鳥 研 報 第9巻 第1号(No.48) the border of their territories (Fig. 7). Most of them were neighbouring territory occupants. Threat-In confronting, one bird threatened another. It frequently resulted in breaking the con- fronting situation. In the case where confronting still continued, chase was acted as stated later. Threatening postures were classified into four patterns as follows; (1) the bird looked upward with the tail upward and sang with the slightly opened bill (Fig. 8-a), (2) it flew up vertically about 50cm height above the ground and alighted at the same place (Fig. 8-b), (3) it flew over the head of opponent and returned back to the same place (Fig. 8-c), and (4) it flew up vertically and fluttered 50-100cm height above the ground (Fig. 8-d). Chase-It was a behavior that territory occupants pursued the intruders, most of which repeated the sound "pipit, pipit". Fight-It was a behavior that two struggling birds tangled together in the air with the bills and the feet. It also occurred before and after chase (Fig. 9). Alert-They frequently alighted on stones or on sand banks in the stream, or perched on dead trees, and seemingly looked round for intruders. Territory occupants did not always last to stay in their territories all day long. They sometimes showed long flights out of their territories. Most of those flight directions stably pointed to Zanbori River flowing northerly, and a few pointed to the main stream of Tama River, flowing southerly. For example, the occupant of the territory 3MB on March 6, 1973, showed the round trips to Zanbori River and to a cultivated land, situated between the drainage and Zanbori River. This individual only took food but did not occupy any territory in the both areas. Also in Zanbori River, a bird showed the round trip to a ajacent cultivated land. Such prominent long flights were also taken by most of the occupants, such as 2DA, 2DB, 2DG, 3JA, 3JB, 3JG, 3MA, 3MB, 3MG, 3DE, 4MA and 4ME. According to the above, at least in the study area, the territory occupants seemingly held one or more undefended feeding sites out of their territories. Territorial birds and pairing behaviors In territory occupation, two cases were observed: firstly, a territory belonged to a Table 1. Numbers of territories occupied by both pair and single bird. (28) 昭 和52年(1977)3月 Wintering ecology of White Wagtail 29 bird, and secondly, it belonged to two birds.