Movement and persistence by Ross’s Geese (Chen rossii) in Canada’s arctic

Abstract

We have been studying population biology of Ross’s Geese south of Queen Maud Gulf (QMG) in Canada’s central arctic from 1989 to 2008. Many Ross’s Geese there nest in a small number of discrete colonies which form the QMG metapopulation. In addition to capture and marking of geese, we have used ground-based sampling of nests to estimate the annual rate of population growth at Karrak Lake, one of the largest colonies within the QMG metapopulation. Between 1993 and 2008, Ross’s Geese at Karrak Lake have been growing in an uninterrupted fashion at about 11% per year and numbered about 726,000 ± 91,000 (95% CL) breeders in 2008. In addition, substantial numbers of Ross’s Geese had colonized an area about 750 km southeast of QMG at McConnell River on the west coast of Hudson Bay (WHB) in 1994. We have been marking Ross’s Geese at WHB from 2001 to 2006. In addition, we used complementary ground-based methods similar to those at QMG to estimate annually the abundance of nesting geese at WHB. The population increased at WHB by 11% per year between 2003 and 2007, a rate very similar to that observed at Karrak Lake near QMG. In 2007, the population of nesting Ross’s Geese at WHB was about 81,000 ± 12,000. In addition to contributions through local recruitment, we wished to better understand the role of movement and source–sink dynamics between QMG and WHB. We used joint multistate–dead recovery mark–recapture models to estimate movement probability of adults between these two regions. The greater likelihood of movement (0.24 ± 0.18) from WHB to QMG, compared to the inverse (0.05 ± 0.04) was restricted to males; there was virtually complete philopatry by females at both study areas. The high rate of philopatry by adult females suggested that population growth in each study area was most likely sustained by in situ recruitment. We also tested and confirmed the assumption that movement probability between regions was unrelated to marker type.