. The Canadian field-naturalist. 588 The Canadian Field-Naturalist Vol. 114 y = + R^ = (p=). 88/89 89/90 9f/92 92/93 y = - R' = (p=) Figure 2. Linear regression of Little Gull counts (corrected for number of visits) in relation to year of count: (above) Autumn; (below) Spring. winter period and 529 during the first part of the spring return. Maximum counts ranged from 1-22 in the autumn/early winter period and 1-78 in the spring return period (Tables 1-2). Thus combined totals were lower in the autumn/early winter than in the spring (Figure I)
. The Canadian field-naturalist. 588 The Canadian Field-Naturalist Vol. 114 y = + R^ = (p=). 88/89 89/90 9f/92 92/93 y = - R' = (p=) Figure 2. Linear regression of Little Gull counts (corrected for number of visits) in relation to year of count: (above) Autumn; (below) Spring. winter period and 529 during the first part of the spring return. Maximum counts ranged from 1-22 in the autumn/early winter period and 1-78 in the spring return period (Tables 1-2). Thus combined totals were lower in the autumn/early winter than in the spring (Figure I). There was a tendency for more Little Gulls to be counted during the autumn/early winter in the first few years of study ( 1988/1989 and 1989/1990) than later, when more Little Gulls were counted in the spring. That was partly because more spring counts were made in recent years (, two counts in spring 1988/1989 compared to 16 counts in 1995/1996; Table 1). However, when we adjusted counts for the number of visits (log-transformed data) the linear regression of spring counts on year demonstrated a marginally significant increase in gull numbers (SLR; Fj ^ = , r^ = , P = ; Figure 2a). Conversely, there was a non-sig- nificant decline in counts of Little Gulls made during the autumn period (F, ^ = , r^ = , P = ; Figure 2b). Although most correlations between autumn/early winter counts of Bonaparte's Gulls and Little Gulls were negative, in only two seasons did they approach statistical significance (1990/1991 r^ = , n=23, P = and 1991/1992, r^ = , n=26, P = ). For the combined spring and fall counts only one of 10 tests was significant (r^ = , n=18, P = ). Discussion Relative importance of the Niagara River Our results suggest that the Niagara River is a very important staging area for Little Gulls, as it is for Bonaparte's Gulls (Kirk and co-workers, unpub- lished manuscript), particularly during the spri
Size: 2133px × 1171px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorottawafi, bookcentury1900, bookdecade1910, bookyear1919
