Feeding Ecology of Greater Snow Goose Goslings in Mesic Tundra on Bylot Island, Nunavut, Canada

Although mesic tundra is a habitat commonly used by arctic-nesting geese, their feeding ecology in this habitat is little known compared to wetlands. Our objectives were to determine the diet and food selection of Greater Snow Goose (Chen caerulescens atlantica) goslings in relation to the nutritional quality of plants growing in mesic tundra habitats on Bylot Island, Nunavut, Canada. We used two different but complementary approaches: examination of esophageal contents of sacrificed wild goslings, and direct observation of the feeding activity of captive, human-imprinted goslings. The latter method was innovative and provided a reliable description of the diet, with results comparable to those obtained from wild goslings. Although mesic habitats have a more diverse floristic composition than wetlands and sparse graminoid cover, Gramineae were preferentially selected and dominated the diet (~50%). The rest of the diet consisted mainly of members of the Juncaceae, Polygonaceae, and Leguminosae families. The diet of very young goslings was diverse, but as they aged and gained efficiency, they concentrated on a few taxa. Goslings ate mostly leaves (~80%), but flowers (~20%) were also important. Food selection was influenced by nitrogen and total phenolic compounds content of plants, but the ratio of phenolic compounds to nitrogen in plant organs was most determinative of food choice. Neutral detergent fiber content of plants did not influence plant selection. Both plant nutritional quality and availability determined gosling diet across different mesic habitats and growing goslings appeared to maximize their intake of metabolizable proteins.

Habitat use and behaviour of Greater Snow Geese during movements from nesting to brood-rearing areas

Many precocial birds make long-distance movements with their young after hatch to reach the best foraging sites. On Bylot Island, Nunavut, a large number of Greater Snow Goose ( Chen caerulescens atlantica L., 1758) families move 30 km from the main nesting colony (MNC) to reach the main brood-rearing area (MBR) soon after hatch. Geese moving from the MNC to the MBR generally rear lighter and smaller goslings than geese that avoid this movement by both nesting and rearing their brood at the MBR. In this study, we tested the hypotheses that use of low-quality habitats and an increase in the time spent walking at the expense of foraging during movements could explain the reduced growth of goslings in those families. We conducted visual observations to compare habitat use and selection as well as behaviour of geese during brood movements from the MNC to the MBR (i.e., at a transit area) with those of families that had already settled at the MBR. We also conducted aerial tracking to monitor habitat use of 16 radio-marked females during and after brood movements. Streams, wet polygons, and lakes, considered high-quality habitats in terms of feeding opportunities and predator refuges, were preferred, while upland, a low-quality habitat, was avoided at both the transit area and the MBR. However, broods were found in the upland habitat more often during movements than once settled on a rearing site. The behaviour of unmarked geese at the transit site did not differ from that of geese at the MBR. We suggest that reduced food intake in low-quality habitats during movements, but not the increase in time spent walking, may explain the reduction in growth observed at fledging in goslings moving from the MNC to the MBR.

Natural infection by intestinal cestodes: variability and effect on growth in Greater Snow Goose goslings (Chen caerulescens atlantica)

We determined the species of intestinal helminths in Greater Snow Goose (Chen caerulescens atlantica) goslings and examined annual variability in infection levels over a 5-year period on Bylot Island, Nunavut. The intestines of 112 wild goslings collected when near fledging were examined. We also evaluated the effect of intestinal parasites on growth and behaviour of captive goslings in a controlled experiment. In 2000, one group (n = 11) was treated with anthelmintic drugs (Piperazine 52 for nematodes and Droncit® for cestodes) and the other (n = 14) was used as a control. Four hymenolepidid cestodes were identified: Drepanidotaenia lanceolata, Hymenolepis barrowensis, Microsom acanthus setigera, and Retinometra longivaginata. No nematodes were detected. Prevalence of intestinal cestodes in wild goslings was 100% but their abundance varied among years (from 28.9 ± 2.7 to 175.2 ± 49.7 (mean ± SE) cestodes per host) and individuals. Captive goslings treated with anthelmintic drugs were free of parasites, whereas all control goslings were parasitized when sacrificed at 36 d, although cestode abundance in the latter group was much lower (4.2 ± 0.7) than in wild goslings. There was no difference in growth rates between treated and control captive goslings until they were 36 d of age. However, treated goslings spent more time feeding than control ones, which suggests an effect of cestodes on host behaviour.