Evaluations of Techniques for Estimating Fall Age Ratios of Canada and Snow Geese

Validity of flock counts, average group-size counts, cannot-net catches, and hunter-bag checks for estimating productivity of lesser snow geese (Anser caerulescens caerulescens) and small Canada geese (Branta cnadensis hutchinsii-parvipes complex) was studied at Sand Lake and Tewaukon National Wildlife Refuges during fall, 1965 and 1966. Age-ratios obtained from flock counts vaired with the number of flocks sampled, wind velocity and amount of sky cover. If adequate sampling sites are selected and weather conditions are standardized, age ratio data from flock counts are of value for assessing productivity. Variation in group composition and number contributed to the bias in average group-size counts of snow geese. Some groups of snow geese were normal families composed of parents and young while other groups contained parents and young plus yearlings and unknown aged adults, possibly non-breeders. Cannon-net catches and hunter-bag checks were biased and favored immature snow and Canada geese because the young birds were not as wary as adults and were more vulnerable to the net and gun. Therefore, cannon-net catches and hunter-bag checks were not reliable for estimating productivity of snow or Canada geese and average group-size counts were no reliable for estimating productivity of snow geese. If Canada geese have similar composition in groups of family size, production estimates from average group-size counts may also be in error for that species. Sex ratios of net-trapped geese showed a preponderance of males for adult Canada and adult and immature snow geese while females were predominant in the immature segment of Canada geese. Bursa of Fabricius measurements showed that bursal depths may be used to classify snow and Canada geese into three age classes: immatures, yearlings and 2-year-olds, and more than 2 years old.

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - Open Access

Discipline thesis:degree_discipline

Wildlife Management

Year

1968

Author dc:creator

• Higgins, Kenneth Frederick

• Natural Resources and Conservation

Statement dc:rights

• <p>No Copyright - Non-Commercial Use Only<br /><a href="http://rightsstatements.org/vocab/InC-EDU/1.0/">http://rightsstatements.org/vocab/NoC-NC/1.0/</a></p>

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/130

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-1130