. The Canadian field-naturalist. Natural history; Sciences naturelles. 218 The Canadian Fbeld-Naturalist Vol. 120 6000 000 5000 000 « 4000000 CO Q 0) 3000000 (/) o O 2000000 1000 000 n Autumn S Spring. Year Figure 4. Stacked area chart showing measured and predicted number of Snow Goose-days on the Fraser River delta since 1987-1998. Data from 1987-1988 through 1991-1992 were measured by Boyd (1995). The remaining data were pre- dicted using linear regression equations developed from data for the 1987-1988 through 1991-1992 period (Boyd 1995), and using population estimates (x values) from Pac
. The Canadian field-naturalist. Natural history; Sciences naturelles. 218 The Canadian Fbeld-Naturalist Vol. 120 6000 000 5000 000 « 4000000 CO Q 0) 3000000 (/) o O 2000000 1000 000 n Autumn S Spring. Year Figure 4. Stacked area chart showing measured and predicted number of Snow Goose-days on the Fraser River delta since 1987-1998. Data from 1987-1988 through 1991-1992 were measured by Boyd (1995). The remaining data were pre- dicted using linear regression equations developed from data for the 1987-1988 through 1991-1992 period (Boyd 1995), and using population estimates (x values) from Pacific Flyway Council (2006*). Regression equations are as follows: (1) Autumn: y = (x) + 448 977 where y = autumn goose-days, and x = annual estimate of Fraser-Skagit segment (P = , r = , df = 4). (2) Spring: y - (x) - 221 987 where y = spring goose-days, and x = annual estimate of Fraser-Skagit segment (P = , r = , df = 4). though geese occur on both deltas simultaneously during autumn and spring, most or all geese use the Skagit River delta for the four to five weeks between these periods. Since the winter of 1978-1979 (when the first photo counts on the Fraser and Skagit deltas were done) the Fraser-Skagit segment grew from ~27 000 birds (Pacific Flyway Council 2006*). Owing to high juvenile production and survival rates of Snow Geese, the Fraser-Skagit segment increased 3- to 4-fold in the late 1970s (Boyd 1995). Numbers of Snow Geese fluctuated in the 1980s then increased thereafter (Fig- ure 3). Figure 3 shows an upward trend in the size of the Fraser-Skagit segment from 1978 through spring 2005 (P < ; r = ; df = 26). Recent surveys indicate that during the winter of 2004-2005 the seg- ment was the highest ever recorded at ~80 000 birds (Pacific Flyway Council 2006*). From 1987-2005 the Fraser River delta sustained an estimated 2-5 mil- lion goose-days annually (Figure 4). Farm fields apparently play an increasingly impor- tant role i
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