Second North American Sea Duck Conference - Patuxent Wildlife ...

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SECOND NORTH AMERICAN SEA DUCK CONFERENCE FORAGING ECOLOGY AND BEHAVIOR OF WILD AND CAPTIVE SPECTACLED EIDERS IN ALASKA William T. O’Connell 1,* , Tuula E. Hollmen 1 , Paul L. Flint 2 , James S. Sedinger 3 , and Christian A. Dau 4 1 Alaska <strong>Sea</strong>Life Center, Seward, AK 99664; bill _oconnell@alaskasealife.org 2 USGS-BRD, Alaska Science Center, Anchorage, AK 99503 3 University of Nevada Reno, Reno, NV 89512 4 USFWS-Migratory Bird Management Division, Anchorage, AK 99503 * Present address PO Box 1322, Bangor, ME 04402 Little is known of spectacled eider (Somateria fischeri) foraging ecology and food habits after hatch. Variation in food availability and abundance can affect the nutritional status of adult females, the growth of offspring, and the survival of adults and juveniles. Further, the foraging behavior and feeding mechanisms of eiders influence what foods are actually consumed and may put eiders at risk of exposure to environmental contaminants. To examine the food habits of adult and juvenile eiders after hatch, we collected benthic samples from brood rearing areas on the Yukon-Kuskokwim Delta, Alaska, in 1997 and 1998. Samples were collected from wetlands used by radio-marked eider broods. Potential food items we identified are primarily Chironomidae larvae, Oligochaetes, other invertebrates and various seeds. We also examined stomach samples from spectacled eiders collected between 1973 and 1978 and from spectacled eider carcasses recovered in 2001. We identified various seeds and insect parts and detected the presence of lead shot pellets in two of the samples. In addition we studied the foraging behavior of 14 captive spectacled eider adults at the Alaska <strong>Sea</strong>life Center in Seward, Alaska in the fall of 2004. During the trials, birds were offered combinations of krill, sago pondweed (Potamogeton pectinatus) seeds, and pea gravel in underwater trays. In all trials the birds consumed the majority of items placed in the trays and apparently did not select for specific items. The foraging ecology of adult and juvenile spectacled eiders is likely influenced by a variety of factors including the type and abundance of foods available. 102 ANNAPOLIS, MARYLAND, USA NOV. 7-11, 2005
SECOND NORTH AMERICAN SEA DUCK CONFERENCE MORPHOLOGICAL AND PHYSIOLOGICAL ASPECTS OF TAKEOFF APTITUDES OF FEMALE COMMON EIDERS IN PRE-LAYING PERIOD Jean-François Ouellet, Magella Guillemette, and Pierre Blier Department of Biology, University of Quebec at Rimouski, 300 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada; jean-francois_ouellet03@uqar.qc.ca The pre-laying period is often associated with an improvement of body condition of females. An extreme case is observed in the common eider (Somateria mollissima). The pre-laying period in female common eiders is characterized by an important increase in body mass caused by follicular growth and the accumulation of body reserves. This weight gain results in dramatic, sex-specific takeoff impairment. Heavy females are frequently observed failing attempts to take off in still air conditions. We investigated how the locomotor apparatus of females responds to this mass increase and tested the hypothesis that pre-laying female common eiders compensate in order to diminish or retard their takeoff impairment. We addressed our question at three organizational levels: i) measurement of flight morphology, ii) weight of flight musculature, and iii) measurement of the activity of key enzymes of aerobic and glycolytic capacity in two locomotor muscles and one structural muscle. All measurements were performed on individuals of both sexes collected around Bicquette island, Quebec, Canada, a large colony found in the St. Lawrence River estuary. Our results indicate that, by the means of phenotypic plasticity and physiological compensation, females adopt strategies enhancing lift production at different organizational levels. However, these strategies do not fully offset weight gain effects. Compared to the larger males, females showed a similar wing area, a hypertrophy of flight musculature, and maintenance of an energy metabolism pathway in pectoralis muscle. The pectoralis muscle of females with higher wing-loading further compensates for their weight gain. Females seem to have reached the upper limit of metabolic power, suggesting the existence of a glycolytic capacity threshold (reflected by body mass-specific pectoralis LDH activity) to takeoff aptitudes in large birds. These results demonstrate that the maintenance of flight aptitudes is an issue of tremendous importance for pre-laying female eiders. NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA 103
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