Working Group on Seabird Ecology (WGSE). ICES CM 2004/C:05 ...

Table 5.7. Approximate numbers (individuals x 1000) and biomass (tonnes) of birds that breed outside NAFO subareas but enter
NAFO 5 and 6 (from ICES. 2003, Table 3.4).
Species Number Biomass
Greater shearwater 1900 2100
Sooty shearwater 410 320
Wilson’s storm-petrel 600 20
Long-tailed duck 230 190
Black scoter 60 60
Surf scoter 120 150
Velvet scoter 100 130
Red-breasted merganser 60 40
Red-necked phalarope 250 10
Grey phalarope 240 10
Bonaparte’s gull 60 10
Ring-billed gull 1500 600
Total 5530 3640
5.2.3 Consumption estimates
Seabirds occupying the NAFO and ICES areas of the North Atlantic consume an estimated 11.5 million tonnes of food
per year with 45% being taken in the western sector and 55% in the east. This total is ca. 10–20% of the total
consumption by the world’s seabirds (max. CI range = 56–133 million tonnes) estimated by Brooke (2003). Although
this percentage seems relatively high, it may reflect both the elevated consumption by seabirds at high latitudes and the
conservative approach of Brooke’s estimate.
The near equality of the overall consumption on both sides of the Atlantic is despite the fact that nearly twice the
number of seabirds occupies the NAFO areas and is a reflection of the huge numbers of small species in the west.
The total food consumption estimates for both the ICES subareas and for the NAFO subareas peak in the summer
season at levels 44% and 54% higher than the respective winter consumption estimates. The elevated energy demand in
summer is primarily caused by increased reproduction activity, but also the larger numbers of birds (and hence higher
biomass) in summer on both sides of the Atlantic. In the ICES area there are 37% more birds (and an 11% higher
biomass) and in the NAFO area 12% more birds (and 16% higher biomass) in summer than in winter. In the NAFO area
the extra food consumption caused by reproduction and the summer visitors from the southern hemisphere outweigh by
far the extra consumption by wintering visitors entering the NAFO area from the ICES area and the eastern Canadian
Arctic (guillemots and seaducks) and leaving the NAFO area for the summer.
Note that while numbers and biomass of seabirds in a given area in a given season are based on maximum numbers in
that season, the food consumption of seabirds occupying the ICES subareas (Table 5.8) and the NAFO subareas (Table
5.9) are calculated based on the number of days each species stays in a given subarea and thus do not directly
correspond to the biomass in Tables 5.5 and 5.6.
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ICES WGSE Report 2004