This study was designed to determine what percent of 1-, 2-, and 3-year-old wild geese (Branta canadensis moffitti) nest in a population of limited size; to compare results with similar information from captive flocks; and, by applying the breeding-age data obtained, to determine the percent of breeding geese in the Flathead Valley population. Five hundred forty-eight known-age Canada geese in the Flathead Valley population were color-marked during four breeding seasons, and the survivors were observed for breeding activity over a 5-year period. Most of the marked known-age geese were located prior to nesting; then the number of nesting birds in each age group was determined by censuses throughout the breeding seasons. A similar experiment was conducted on two captive flocks. No 1-year-old birds nested in either the wild or the captive populations. Between 27 and 36 percent of the 2-year-old wild geese nested, but only 17 percent of the captive 2-year-olds did so. All of the 3-year-old wild birds nested, but only 64 percent of the captives nested. Since the proportion of birds breeding in captive and in wild flocks appears to be markedly different, the breeding data from captive flocks cannot be used to determine the breeding age or the percent of breeding birds in a wild population. The breeding-age statistics obtained from the wild population, when applied to life-table data, showed that during a population-turnover period of 5 years only 10.2 percent of a generation of geese in the Flathead Valley, Montana, attained breeding age and survived to nest. This calculation was made on the assumption that one-third of all 2-year-old geese nest. In order to understand the population dynamics of Canada geese and to interpret more accurately life equations and life tables constructed for the species, it is essential to evaluate breeding-age data on captive flocks and to obtain more precise information on the breeding age of wild birds. Various authors have studied the breeding age of Canada geese in captive and semicaptive flocks. Elder (1946:105) stated that none of the pinioned geese in the flock at Bright Land Farm, Illinois, nested in their first or second years and only 25 percent nested in their third year. Kossack (1950:628), studying the same flock, found that none nested as 1-year-olds, 7.8 percent nested as 2-year-olds, and 20 percent nested as 3-year-olds. Kossack apparently included in his findings both wing-clipped and full-winged birds. Balham (1954), working with a flock in Manitoba, stated that only a small percentage of geese nested as 2-year-olds. Hanson (1949:181-182), working with captured wild geese (Branta canadensis interior) on the Horseshoe Lake Game Refuge in Illinois, separated 1-year-old females from older females by determining the presence or absence of an occluding membrane over the opening of the oviduct. All but one of 2/2-year-old females had open oviducts. If this was an accurate way of judging whether these females had nested, then about 94 percent had nested at 2 years. In his most recent publication, Hanson (1962:15) indicates uncertainty as to breeding among 2-year-olds and points out the need to determine more precisely what percent of the 2-year-old females nest in their third spring. He says, however, "At the present stage of our knowledge, predictions of populations must be based on the assumption that all females attempt to nest 1Contribution from the Montana Cooperative Wildlife Research Unit, U. S. Fish and Wildlife Service, Montana State Fish and Game Department, Montana State University, and Wildlife Management Institute cooperating. The study was partially supported with Federal Aid in Wildlife Restoration funds under Pittman-Robertson Project W-71-R, Montana State Fish and Game Department.