Brood Movements of Eastern Prairie Population Canada Geese: Potential Influence of Light Goose Abundance

Abstract During the summers of 2000–2002, we used radio telemetry to document Eastern Prairie Population (EPP) Canada goose (Branta canadensis interior) brood movements and use of brood-rearing habitat. We compared these data with similar data collected in 1976–1978 (Didiuk 1979), prior to a significant increase in the size of the midcontinent light goose (lesser snow geese [Chen caerulescens] and Ross's geese [C. rossii]) population and consequent habitat alteration near Cape Churchill, Manitoba. Since the late 1970s, use of traditional EPP Canada goose brood-rearing areas by light geese has increased significantly near Cape Churchill, and the density of nesting EPP Canada geese has declined. Alteration of brood-rearing habitat has been hypothesized as a cause of the decline in EPP breeding density, as natal dispersal to more distant brood-rearing areas may influence future recruitment into the local breeding population. In 1976–1978, 20 (95%) of 21 radio-marked broods nesting in beach ridge/sedge meadow habitat moved to salt marsh brood-rearing areas; however, only 5 (19%) of 27 Canada geese, nesting in the same habitat, made initial movements to these traditional salt marsh brood-rearing areas in 2000–2002. In 2000–2002, 30 (75%) of 40 geese with broods made initial movements to beach ridge/sedge meadow habitat—10 of these broods eventually moved to salt-marsh habitats later in the brood-rearing period (χ̄ date = 22 days postmedian hatch). Mean brood home range size from 2001–2002 in coastal and inland habitats nearly doubled compared to the mean brood home range size during 1976–1978. Eastern Prairie Population Canada geese currently use brood-rearing habitat other than the coastal salt marshes they used prior to habitat alteration resulting from foraging by light geese. A shift in the use of brood-rearing habitat could potentially reduce nest densities on the study area if first-time breeders nest closer to distant brood-rearing areas. The impact of alternative brood-rearing habitat on gosling growth and survival for EPP geese is unknown, but foraging in poorer quality brood-rearing habitat may also contribute to the observed decline in nesting density.