Re-evaluating the use of beached bird oiling rates to assess long-term trends in chronic oil pollution |
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Authors: | Wilhelm Sabina I Robertson Gregory J Ryan Pierre C Tobin Stan F Elliot Richard D |
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Affiliation: | a Canadian Wildlife Service, Environment Canada, 6 Bruce Street, Mount Pearl, NL, Canada A1N 4T3 b Wildlife Research Division, Environment Canada, 6 Bruce Street, Mount Pearl, NL, Canada A1N 4T3 c Newfoundland and Labrador Environmental Association, Ship Cove, NL, Canada A0B 2Y0 d Wildlife Research Division, Environment Canada, 17 Waterfowl Lane, P.O. Box 6227, Sackville, NB, Canada E4L 1G6 |
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Abstract: | The oiling rate (oiled birds/total birds) has become the international standard to analyze beached bird survey data. However, this index may not reliably track long-term changes in marine oil pollution in regions where other activities that kill seabirds vulnerable to oil, such as hunting and gill-netting, are also changing. We compare the oiling rate from beached bird surveys conducted in southeastern Newfoundland between 1984 and 2006 to an alternative approach, namely trends derived from a model examining the linear density of oiled birds (birds/km). In winter, there was no change in the oiling rate since 1984, while in summer oiling rates significantly increased. In contrast, the number of oiled birds/km showed a significant decline in both winter and summer. The discrepancy in these trends was attributed to steep declines in the number of unoiled birds found in both seasons. In winter, the decline in unoiled birds/km was related to a reduction in the legal murre hunt and less onshore winds, while in summer a reduced cod fishery resulting in fewer murres drowning in nets and warming summers may have lead to the decline. The significant declines in oiled birds/km over the past three decades are hopefully an indication of less oil being present in the marine environment. Although oiled bird densities since 2000 have remained relatively low for the region (winter: 0.58 birds/km, summer: 0.27 birds/km), they still exceed densities reported elsewhere in the world. |
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Keywords: | Beached bird surveys Fisheries bycatch Murre hunt Newfoundland Oil pollution Uria spp |
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