Because of the tremendous interest in Cackling Geese, we thought Ontbirders would be interested in this recent paper published electronically in The Auk that describes a hybrid zone between Canada and Cackling Geese just west of Hudson Bay. See abstract below.
ABSTRACT: "We studied patterns of geographic variation in structural size and genetic characteristics of white-cheeked geese inhabiting coastal areas of Hudson Bay from northern Manitoba to southern Nunavut, Canada to determine the degree of morphological and spatial overlap, if any, between Cackling Geese (Branta hutchinsii) and Canada Geese (Branta canadensis) in this region. Most Canada Geese occurred in subarctic habitats south of 59 N latitude, and most Cackling Geese occurred in arctic habitats north of 60 N, but the two species overlapped in a narrow zone between 59 N and 60 N latitude that coincided with the ecotone between subarctic and arctic ecozones. Mismatches between morphological and genetic characteristics of some individual females suggested that introgression had occurred in this area, and contrasting patterns in the nuclear and mitochondrial DNA (mtDNA) were consistent with female natal philopatry and male-biased dispersal. Evidence of introgression in the nuclear genome was geographically more widespread than was evidence of introgression in the mtDNA genome. We suggest that the persistence of Canada Goose mtDNA in phenotypic Cackling Geese is a result of historical hybridization events that occurred when the arctic-subarctic ecotone was located farther north during a warmer climatic period. Despite evidence of introgression, most birds that we sampled appeared to belong to one or the other parental species based on their consistent identification using morphological, mtDNA, and nuclear DNA characteristics. We suggest that the area of overlap represents a tension zone between Canada Geese and Cackling Geese that is maintained by behavioral and ecological factors that limit effective dispersal." COMMENT: There is no reason to believe that this hybrid zone is restricted to the study area. It possibly extends along the contact zone of the two species from Hudson Bay to Alaska. A hybrid family group with two flightless goslings was captured in Ontario along the coast of Hudson Bay in 2006. CITATION: A Hybrid Zone between Canada Geese (Branta canadensis) and Cackling Geese (B. hutchinsii) by James O. Leafloor, Jennifer A. Moore and Kim T. Scribner. Published electronically 29 March 2013 in The Auk. Ron Pittaway and Jean Iron Toronto, Ontario _______________________________________________ ONTBIRDS is presented by the Ontario Field Ornithologists - the provincial birding organization. Send bird reports to birdalert@ontbirds.ca For information about ONTBIRDS visit http://www.ofo.ca/
