HARLEQUIN DUCKS (HISTRIONICUS HISTRIONICUS) IN MAINE, 1950–1999

Abstract

We estimate between 1,150 to 1,300 Harlequin Ducks wintered in Maine in the late 1990s. This represents over 50% of the total known wintering population in eastern North America. About 75% of these wintering birds in Maine were located in the Isle au Haut area from Vinalhaven to Swans Island. Smaller concentrations of birds were also present in eastern Hancock County (Sally Islands area) and York County (Cape Neddick area). At four groups of islands in the Isle au Haut area, numbers show a pattern of decline from 1989 to 1993 followed by increases since then. In contrast, the maximum number of birds reported each winter in York County has increased from about five birds in 1955 to about 75 birds in 1999 (rs = 0.73, n = 42, P < 0.001). The proportion of males to females observed during mid-winter counts increased from a low of 0.8:1.0 in 1992 to a high of 1.2:1.0 in 1996 (rs = 0.54, n = 35, P = 0.001) and averaged 1.0:1.0 (n = 35, SD = 3.5) from 1989–99. Given the small numbers and limited distribution of Harlequin Ducks in Maine, they should remain under full protection in the foreseeable future.