The Status of the Southernmost Populationof the Harlequin Duck Histrionicus histrionicus in Northeastern Nagano Prefecture

Abstract

A female with four juveniles and seven female-type birds of unknown age of the Harlequin Duck Histrionicus histrionicus were observed during the breeding seasons of 2015 and 2016, respectively, in the Zakko River, northeastern Nagano Prefecture. During the breeding season from 2017 to 2020, the present and breeding status of the Harlequin Duck population was investigated. In all the years surveyed, several Harlequin Ducks were observed, and flightless chicks with natal down were found in 2019 and 2020. Therefore, the study area is the southernmost breeding site of the Harlequin Duck in Japan.