- 日本鳥類標識協会誌 (ISSN:09144307)
- vol.8, no.2, pp.53-59, 1993 (Released:2015-08-20)
Red-necked Phalarope Phalaropus lobatus is a common spring and autumn migrant along the Japanese coast, and is also occasionally seen in small flocks inland. At about 9:00 PM on the night of September 13th, 1993, a flock of 100 Red-necked Phalarope strayed into Okoppe-cho Baseball Stadium (Monbetsu County, Eastern Hokkaido -44°28′N, 143°08′E). Presumably these birds had been attracted by the bright stadium lights (similar incidents have been recorded in the past for this species, but not during the last 20 years). The birds flew around the stadium, sometimes landing for brief intervals, for about 30 minutes before departing. Some of the birds crashed into the standium fence and were killed or injured. 6 of these were recovered as specimens to be measured and analyzed at the Natural History Museum and Institute. Chiba (specimen No. CBMZB1775-CBMZB1780). All of the recovered specimens were juveniles which had not yet molted into the 1st winter plumage. All specimens showed pale cream coloration from throat to breast, and diagnostic dark brown markings on the tertials. Juvenile feathers also remained on the mantle and wing-coverts. Observations at the stadium confirmed that no adults were present in the flock. Large flocks of Red-necked Phalarope, numbering from 1000-3600 individuals, are frequently observed during the spring migration period. These large flocks, however, are composed of adults, and flocks, however, are composed of adults, and flocks of juveniles number only in the low one-hundreds. This indicates that adults and juveniles migrate separately in spring. The data discussed here supports the contention that juveniles and adults also migrate separately in autumn, with juveniles leaving the breeding grounds later than adults. Unfortunately, age-composition data is not available for earlier incidents.