Dynamics of foraging behavior associated with variation in habitat and forage availability in captive black brant (Branta bernicla nigricans) goslings in Alaska
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Authors: M. P. Herzog, and J. S. Sedinger
Date: 2004
Journal: The Auk
Volume: 121
Number: 1
Pages: 210-223
Summary of Methods: The effect of different grazing intensities (no grazing, light, moderate, and heavy) of Black Brant (Branta bernicla) gosling on grazing lawns planted to Carex subspathacea and native slough levees (T. palustris) was measured on the Yukon-Kuskokwim Delta, Alaska (61Ëš N, 165Ëš W). Above ground biomass and offtake of biomass was measured pre-, mid-(after 4 h), and post-trial (8 h) in both habitats. Offtake was calculated as the difference between the average biomass measured before and after a given portion of treatment. Every two hours of the 8 hour grazing treatment gosling grazing behavior (feeding or not) was recorded every minute for one hour.
Article Summary / Main Points: Forage production was not enhanced by grazing in either vegetation type. Biomass and offtake in C. subspathacea were higher in lightly grazed plots than in the heavily grazed plots. In the slough levee habitat, the level of grazing did not affect biomass or offtake. Overall the grazing level did not affect thefeeding time between the two habitats, though feeding time declined as gosling mass increased. After controlling for variation due to date, C. subspathacea production was greater in the lightly grazed treatment than other two treatments and no differences occurred betweenthe medium and heavy grazed treatments. Gosling herbivory, regardless of intensity, reduces available forage during the fledging season, which may affect the future survival and growth of goose populations in this area.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 238 Yukon-Kuskokwin Coastal Plain
Agrovoc Control Words: Riparian zones Grazing Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: carex subspathacea, triglochin palustris, herbivory, forage availability, foraging efficiency, grazing intensity, black brant geese, branta bernicla nigricans
Annotation: The results of this study are limited to areas with grazing lawns and slough leeves. The results also show how grazing behavior and forage availability changes under different grazing pressures. These results are not applicable for long-term grazing management situations because of the duration of the study were limited to one year.
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