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Grand Teton National Park Report

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During the 1986 field season, 89 Harlequin Ducks (Histrionicus histrionicus) were individually identified on four backcountry streams and the Snake River. Forty-eight birds were banded (15 adults and 33 young of the year). Twelve adults and one young of the year banded in 1985 returned to the study area. Eight broods were found. Hatch dates ranged from 15 July to 1 Aug with a mean brood size of 5.4. An estimate of age span at different plumage subclasses was determined through repeated observations. Age at first flight was found to be 42 days. Moose Creek produced the most broods (4). Insect samples were taken at feeding sites along four streams on a monthly basis to give some insight into food resources. Eight measurements of habitat were taken at points where ducks were observed and at 200 m intervals along the streams which they were found. Five hens which showed up in late June 1985 as unpaired birds returned to the same streams this season with mates. None of the marked hens with broods found in 1985 were seen on the study area in 1986.