Report Nr. 3225 Morphometric Comparison of Resident Giant Canada Geese in Northern and Southern Michigan

Body size of Canada geese (Branta canadensis) varies by subspecies, generally decreasing as geographic latitude of breeding grounds increases. Morphological measurements of harvested geese have been used to determine breeding ground affiliation to improve harvest management strategies for individual population units. Giant Canada geese (B. c. maxima) nest throughout Michigan and currently comprise about 50% of the state's annual Canada goose harvest. Much of this harvest occurs during special "early" and "late seasons" established to control populations of resident giants. Body part measurements have been used to evaluate the effectiveness of special seasons at targeting giant Canada geese. Considering the potential misclassification of resident Northern Michigan geese in the harvest, we wanted to determine if data used to establish midpoints were representative of Michigan giants from both northern and southern regions. Therefore, the researchers compared culmen size of giant Canada geese residing in Northern vs. Southern Michigan in an effort to fine tune differentiation criteria to better proportion the Michigan goose harvest into resident giants and migrant interiors. As a result, the researchers found Michigan giant Canada geese vary in size by latitude. During 1994, geese measured in Sault Ste. Marie were smaller than geese from Escanaba, which were smaller than Southern Michigan geese. When comparing 1994 data sets and measurements collected in previous years, geese from Sault Ste. Marie were consistently smaller than Southern Michigan geese. Canada geese measured in Escanaba were generally smaller than Southern Michigan geese and larger than Sault Ste. Marie geese.