Search

Effective use of seabirds in ecotoxicology monitoring programs ideally requires detailed knowledge of their ecology. Environment Canada recently expanded the Great Lakes Herring Gull Larus argentatus Monitoring Program to a national contaminants monitoring program, utilizing the Glaucous-winged Gull L. glaucescens on the west coast of Canada. The utility of the Glaucous-winged Gull as a marine monitoring species hinges on its consumption of a marine-based diet; however, there is a lack of recent and reliable diet data for this species. Using conventional analysis, we studied dietary ecology at two monitored colonies to elucidate adult diet before egg laying and during incubation, to investigate intra-colony dietary shifts over the breeding season, to examine inter-colonial dietary variation, and to compare findings with historical studies from the early 1970s and 1980s. Results indicate that breeding gulls forage in an opportunistic manner, with marine prey sources predominant at all colonies and breeding stages, but with a wider variety of prey types consumed in locations close to urban development. Chicks at both colonies were provisioned primarily with fish; however, variation in chick diet between 2009 and 2010 indicates that diet can vary considerably on a short time scale. The occurrence of fish fed to chicks appears to have shifted composition from herring Clupea pallasii in the 1980s to primarily Pacific Sand Lance Ammodytes hexapterus at both colonies in 2009 and 2010. Compared with historical records, gulls consumed fewer anthropogenic items and more fish in the Strait of Georgia, whereas diet off the west coast of Vancouver Island appears to have been consistently marine. [ABSTRACT FROM AUTHOR]

During the late 20th Century, due to decreases in both contamination and persecution, bald eagle (Haliaeetus leucocephalus) populations increased dramatically. Currently, mechanisms regulating eagle populations are not well understood. To examine potential regulating processes in the Pacific Northwest, where eagles are no longer primarily regulated by contaminants or direct persecution, we examined bald eagle reproductive success, breeding populations, winter populations, mortality, and salmon stream use. Wintering and breeding eagle populations in south-coastal British Columbia (BC) quadrupled between the early 1980s and the late 1990s, and have since stabilized. Density-dependent declines in reproduction occurred during 1986-2009, but not through changes in site quality. Mid-winter survival was crucial as most mortality occurred then, and models showed that density-dependent reductions in population growth rates were partially due to reduced survival. Wintering eagles in British Columbia fed heavily on chum salmon (Oncorhynchus keta) runs, and then switched to birds in late winter, when mortality was highest. Eagles tended to arrive after the peak in salmon availability at streams in BC as part of a migration associated with salmon streams from Alaska to northern Washington. Eagles were most abundant in southern BC during cold Alaskan winters and in years of high chum salmon availability.We suggest that eagle populations in the Pacific Northwest are currently partially limited by density on the breeding grounds and partially by adult mortality in late winter, likely due to reduced late winter salmon stocks forcing eagles to exploit more marginal prey supplies. Larger eagle populations have affected some local prey populations. [ABSTRACT FROM AUTHOR]

Osprey (Pandion haliaetus) eggs were collected from 1991 to 1997 at nests (n = 121) upstream and downstream of bleached kraft pulp mills and at reference sites in the Fraser and Columbia River drainage systems of British Columbia, Washington, and Oregon. Blood samples were collected from nestling ospreys during the 1992 breeding season on theThompson River. Samples were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and -dibenzofurans (PCDFs). Mean concentrations of 2,3,7,8-TCDD were significantly higher in eggs collected in 1991 at downstream compared to upstream nests near pulp mills at Kamloops and Castlegar, British Columbia. There were no significant temporal trends in 2,3,7,8-TCDD, -TCDF or other measured compounds at a sample of nests monitored between 1991 and 1994 downstream of the Castlegar pulp mill, despite changes in bleaching technology (CIO2 substitution). However, by 1997 concentrations of 2,3,7,8-TCDD and -TCDF were significantly lower than previous years in nests sampled downstreamat both Castlegar and Kamloops. An unusual pattern of higher chlorinated PCDDs and PCDFs was found in many of the osprey eggs collected in this study, and considerable individual variation in the pattern existed among eggs from the same site. For example, eggs from four different nests at one study area (Quesnel) on the Fraser River had concentrations of 1,2,3,4,6,7,8-HpCDD ranging from <1 to 1,100 ng/kg and OCDD from <1 to 7,000 ng/kg wet weight. Higher mean concentrations of HpCDD and OCDD were found in eggs from the Thompson River, a tributary of the Fraser, compared to the Columbia River, and concentrations were generally higher at nests upstream of pulp mills. In plasma samples, 1,2,3,4,6,7,8-HpCDD and OCDD were the main compounds detected, with no significant differences measured between samples upstream versus downstream or earlier versus later in the breeding season. Use of chlorophenolic wood preservatives by lumber processors was considered th [ABSTRACT FROM AUTHOR]