Body Size and Condition of Male Mallard During Mid-winter in North Dakota, USA

Abstract

Abstract Mallard (Anas platyrhynchos) may winter in northern areas if they have access to adequate food and open water. We compared individual body size (indexed by first principal component scores from three morphometric measurements) and body condition (body mass adjusted for body size) of male Mallard wintering in North Dakota, USA during 1996-99 with a baseline reference group of Mallard from Ontario, Canada measured during late summer. Size and condition of Mallard wintering in North Dakota was also compared, using a sample from a traditional wintering area in Arkansas, USA. Male Mallard body size and condition in North Dakota relative to weather severity during mid-winter was assessed. Body size of adult males in North Dakota was significantly greater than that of birds from Ontario, but similar to those from Arkansas. Adult males remaining in North Dakota during the coldest winter were not larger than those remaining in North Dakota during milder winters. Immature males in North Dakota were signifi...