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Browsing Researcher Spotlights by Author "Abraham, Kenneth F."
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Item Open Access Goose-induced Changes in Vegetation and Land Cover between 1976 and 1997 in an Arctic Coastal Marsh(Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, 2005) Abraham, Kenneth F.; Jefferies, Robert L.; Rockwell, Robert F.Since the 1970s, a breeding colony of lesser snow geese (Chen caerulescens caerulescens L.) at La Pérouse Bay, Manitoba, has grown 8% annually. This increase has led to significant loss of plant cover in all major salt- and freshwater coastal habitats between 1976 and 1997. A series of transects established in 1976 was resurveyed in 1997. Exposed sediment, extent and type of vegetative cover, and aquatic areas were recorded along transects using a classification of 12 a priori classes. Five regions within the colony were identified, and changes in vegetation cover differed among these and depended on unique combinations of vegetation class and year. Grubbing by geese has led to loss of graminoid plants, especially in intertidal and supratidal marshes. Exposed sediments have largely replaced previously vegetated areas since 1976. Species characteristic of disturbed sites have colonized exposed sediment with the most abundant species varying according to soil conditions. In intertidal marshes, willow cover declined in association with the development of hypersalinity after loss of the graminoid mat, but willow cover increased at the base of well-drained beach ridges and in a river delta with ample winter snow accumulation and freshwater flow in spring that protected ground vegetation. Most of the expected successional trends associated with isostatic uplift and changes in soil organic matter failed to occur because of intense goose foraging throughout the 20 years. The likelihood of sustained recovery of plant communities in the immediate coastal zone is very low, as long as goose numbers continue to increase. Indirect effects of vegetation loss (e.g., hypersalinity) and subsequent erosion of exposed sediments following grubbing will delay plant colonization and retard succession.Item Open Access Nutrient Allocation Strategies to Eggs by Lesser Snow Geese (Chen caerulescens) at a Sub-Arctic Colony(University of California Press, Jan-11) Hobson, Keith A.; Sharp, Christopher M.; Jefferies, Robert L.; Rockwell, Robert F.; Abraham, Kenneth F.The relative allocation of endogenous- and exogenous-derived nutrients to reproductive investment in Arctic-nesting geese is affected by body size, migration distance, and proximate conditions on the wintering, staging, and breeding grounds prior to clutch initiation. We used C13 and N15 measurements of muscle tissue and egg lipid-free yolk and albumen and C13 analysis of abdominal fat and egg yolk lipids, together with isotopic analyses of foraging plants, to quantify the relative use of endogenous and exogenous reserves in egg production in a breeding population of sub-Arctic Lesser Snow Geese (Chen caerulescens caerulescens) on the Cape Churchill Peninsula, Manitoba, from 2005 to 2008. We used a concentration-dependent, two-isotope, three-source Bayesian (SIAR) mixing model to derive estimates of endogenous reserves to egg macronutrients and a single-isotope (C13), two-source (exogenous vs. endogenous) Bayesian model to estimate the source of lipids to eggs. Endogenous protein contributions to eggs were similar to those found using identical Bayesian analytical methods for the larger-bodied Greater Snow Goose (Chen caerulescens atlantica) breeding in the Canadian High Arctic and were on the order of 30%. However, endogenous lipid contributions were considerably greater for the population of Lesser Snow Geese (mean annual contribution of 55.5% vs. 22.3%). This suggests that advantages of larger body size for transport of body lipid reserves for long distances may be countered by the need to use lipids to fuel migration over greater distances. In addition, feeding opportunities of Greater Snow Geese upon arrival at their more distant breeding sites were likely adequate to offset a shorter breeding season and longer development times for offspring than at lower-latitude sites.Item Open Access The Birds of Wapusk National Park(Parks Canada, 2009) Rockwell, Robert; Abraham, Kenneth F.; Witte, Christopher; Matulonis, Paul; Usai, Michael; Larsen, Drake; Cooke, Fred; Pollak, Diana; Jefferies, Robert L.