Weights of Branta canadensis interior during Winter

Abstract

Based on weights of Branta canadensis interior obtained from three sampling periods during winter 1964-65 at Crab Orchard National Wildlife Refuge, Illinois, the following results and conclusions emerged: adults expectedly lost weight in late winter; yearlings and immatures did not lose weight through the winter; geese at Crab Orchard were usually heavier and did not show as many nor as large weight losses as reported from other southern Illinois localities, probably because of the relationships of numbers of geese and available food; Crab Orchard geese appeared to be in excellent condition throughout the winter. Concern has been expressed over food supplies and weight losses of Canada geese during winter in southern Illinois (Elder 1946). Approximately 200,000 B. c. interior concentrate largely on three refuges totaling approximately 36,000 acres (Crab Orchard National Wildlife Refuge, Union County and Horseshoe Lake state refuges). Knowledge of weights of geese from these large concentrations and the factors that influence weight fluctuations serve as indices to the birds' efficiency in obtaining food and food availability on refuges and adjacent countryside. Elder (1946) and Hanson (1962a) studied Canada goose weights in southern Illinois (Horseshoe Lake and Union County refuges). Because there are important differences in management and goose populations at Crab Orchard as compared to the other refuges, 559 Canada geese were weighed at Crab Orchard during the winter of 1964-65. Additionally, more refined methods of age identification, especially of yearlings (Hanson 1962b), and increased knowledge of the taxonomic identity of geese (Hanson, personal communication) 1 This work was carried out in conjunction with a study of Canada goose behavior supported by the National Science Foundation (GB-623); additional support was provided by the Cooperative Wildlife Research Laboratory, Southern Illinois University, Carbondale, Dr. W. D. Klimstra, Director. 2 Present address: Canadian Wildlife Service, 114-A Garry Street, Winnipeg 1, Manitoba. 412 provided the basis for better estimating weight fluctuations of B. c. interior. L. A. Mehrhoff, Jr., Project Manager, and Robert G. Personius, Refuge Manager, Crab Orchard National Wildlife Refuge, are acknowledged for their cooperation. J. Robert Rice, Crab Orchard Refuge, conducted most of the trapping and assisted in weighing geese, as did Wendell E. Crews, Cooperative Wildlife Research Laboratory, Southern Illinois University. Dr. H. C. Hanson, Illinois Natural History Survey, provided access to unpublished data which made possible the identification of Canada geese other than B. c. interior. Dr. W. D. Klimstra provided helpful criticism of the