The Steller's eider (Polysticta stellen] is apparently extinct as a breeding bird on the Yukon-Kuskokwim (Y-K) delta, one of two areas in Alaska where it was a regular breeder. Once considered a common breeding bird on the Y-K delta, it has not been found nesting since 1975, despite recent extensive geographic coverage of waterfowl habitats and ground searches of historically important nesting areas. The Y-K delta was the only known subarctic breeding area in the species' range. Size of the former population and reasons for its disappearance are unclear, but possible factors responsible for the decline include changes in patterns of movement and increased mortality resulting from overharvest, predation, habitat change, weather, and reduction in food. The Steller's eider is now considered a rare species in the Yakutsk Republic, U.S.S.R., the center of the world breeding range. The North American population is now restricted to a small geographical area near Barrow and it has not yet received special consideration or protection comparable to that in the U.

Environmental regulations governing industrial activities in tundra environments stem largely from the expected ecological effects of the activities. One of the major ecological effects of industrial activities is the surface subsidence associated with thermokarst, which can result in changes in primary and secondary production. The primary production changes associated with thermokarst are strongly governed by three ecosystem properties--soil temperature, water regime, and nutrient availability. Most disturbances set in motion a more-or-less predictable sequence of landscape change related to these properties: soil warming, thermokarst, surface flooding, accelerated organic matter decomposition, and increased nutrient availability. The warmed soil and the enhanced nutrient availability typically lead to increased annual primary production, increased dominance by graminoids, and reduced plant species diversity. These vegetational changes may in turn potentially enhance secondary production, but in general these second-level responses have yet to be quantified. More information is needed about the food-chain effects of tundra landscape disturbances before regulators can make well-informed predictions of impacts or plan useful habitat rehabilitation.

ABSTRACT. Reproductive success and foraging effort of Pacific loons (Gavia pacifica) were compared between impoundments and natural ponds in the Prudhoe Bay oil field, Alaska, in 1992 and 1993. Pacific loons successfully reproduced on both impoundments and ponds. Though success tended to be lower on impoundments, no significant differences were detected between the two water body types. The principal cause of reproductive failure on both impoundments and ponds in 1993 appears to have been predation by arctic foxes (Alopex lagopus) during incubation. Predation losses on impoundments often were associated with large water-level drawdowns, which apparently increased opportunities for predation of stranded clutches. I found no differences in chick mortality or adult foraging effort between impoundments and ponds. Over 99% of the prey items delivered to chicks were invertebrates captured in freshwater wetlands. Reproductive output of Pacific loons may be improved by increasing the stability of water levels at impoundments used for nesting. I found no evidence that draining impoundments would improve habitat for loons (or invertebrate-eating waterfowl species) at Prudhoe Bay.Key words: Pacific loon, Gavia pacifica, Prudhoe Bay, impoundments, impact assessment, Alaska RÉSUMÉ. En 1992 et 1993, on a établi une comparaison du taux de réussite de la reproduction et de la quête de nourriture du huart du Pacifique (Gavia pacifica) entre les bassins de retenue et les étangs naturels situés dans le champ pétrolifère de Prudhoe Bay en Alaska. Le huart du Pacifique se reproduisait bien sur les bassins comme sur les étangs. Malgré un taux ayant tendance à être plus faible sur les bassins, on n'a pas remarqué de différences notables entre les deux nappes d'eau. En 1993, la raison principale de l'échec de la reproduction sur les retenues comme sur les étangs semble avoir été la prédation effectuée par le renard arctique (Alopex lagopus) au cours de l'incubation. Les pertes dues à la prédation sur les bassins étaient souvent liées à de grands rabattements de nappe qui, selon toute apparence, facilitaient l'accès des prédateurs aux pontes échouées. On n'a trouvé aucune différence dans la mortalité juvénile ou dans la quête de nourriture entre les bassins et les étangs. Plus de 99 p. cent des proies rapportées aux poussins étaient des invertébrés capturés dans des marais d'eau douce. On pourrait rendre la reproduction du huart plus efficace en préservant la stabilité du niveau des eaux dans les bassins qui servent à la nidification. On n'a pas trouvé de preuves à l'effet que le drainage des bassins améliorerait l'habitat du huart (ou des espèces d'oiseaux aquatiques se nourrissant d'invertébrés) à Prudhoe Bay.Mots clés: huart du Pacifique, Gavia pacifica, Prudhoe Bay, bassins de retenue, évaluation environnementale, Alaska Traduit pour la revue Arctic par Nésida Loyer.

ABSTRACT. Black brant (Branta bernicla nigricans) and lesser snow geese (Chen c. caerulescens) breeding in and near arctic Alaska oil fields could be affected by oil development actions such as releases of contaminants, alteration of tundra surfaces, creation of impoundments, and human activities. These actions could affect geese directly (e.g., through oil spills) or indirectly (e.g., by altering food supplies or predator populations). Studies to date indicate no changes in the distribution, abundance, or reproduction of these geese that clearly can be attributed to development; rather, their numbers and recruitment have responded in the oil fields, as elsewhere, mainly to weather and predation. When snowmelt in spring is later than usual, the birds postpone or forego nesting, with consequent diminishment in recruitment. Predation by arctic foxes (Alopex lagopus), glaucous gulls (Larus hyperboreus), and grizzly bears (Ursus arctos) sometimes causes substantial losses of eggs and young, and predation by ravens (Corvus corax) has also been observed. Development-related changes in weather (microclimate) and loss of feeding habitat have involved small percentages of the total areas traditionally used, and populations of the birds probably have not been affected by these changes. Some studies and observations suggest that development has elevated local populations of some predators, but whether the level of predation on geese has in consequence risen above that which would have occurred in the absence of development is unknown; further investigation of this mechanism of potential impact is recommended.Key words: Brant, Branta bernicla, snow goose, Chen caerulescens, oil development, Alaska, impact assessment, predation, nutrition RÉSUMÉ. La bernache noire (Branta bernicla nigricans) et la petite oie des neiges (Chen c. caerulescens) nichant dans les champs pétrolifères de l'Alaska ou à proximité pourraient être affectées par des actes reliés à l'exploitation pétrolière, tels que le déversement d'agents de pollution, les modifications à la toundra de surface, la création de bassins, et par l'activité humaine. Ces interventions pourraient affecter les oies de façon directe (p. ex., par le biais de déversements de pétrole) ou indirecte (p. ex., en modifiant l'approvisionnement alimentaire ou les populations de prédateurs). Jusqu'à l'heure actuelle, les études ne montrent pas de changements dans la distribution, l'abondance ou la reproduction de ces oies, dont la cause puisse être clairement attribuée à l'exploitation; dans les champs pétrolifères, le nombre d'oies et leur augmentation ont surtout réagi, comme ailleurs, au climat et à la prédation. Quand la fonte des neiges printanière a lieu plus tard que d'habitude, les oiseaux retardent la ponte ou s'abstiennent de pondre, ce qui entraîne moins d'augmentation. La prédation par le renard arctique (Alopex lagopus), le goéland bourgmestre (Larus hyperboreus) et le grizzli (Ursus arctos) entraîne parfois d'importantes pertes d'oeufs et d'oisons, et on a également observé...

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