. The Canadian field-naturalist. 346 The Canadian Field-Naturalist Vol. 83. Figure 3. Vista of Islands to show rocky and sparsely-vegetated as well as "wooded" islands. Note abrupt shorelines and driftwood. 3). This also may be due to varying water levels since the levels were reported- ly several feet lower than normal. Because of the size and depth of Great Slave Lake, it becomes icefree several weeks after small lakes on the mainland. In general, the phenology of the area was between 2 and 3 weeks behind that of the mainland. Undoubtedly, this has an important bearing on the speci
. The Canadian field-naturalist. 346 The Canadian Field-Naturalist Vol. 83. Figure 3. Vista of Islands to show rocky and sparsely-vegetated as well as "wooded" islands. Note abrupt shorelines and driftwood. 3). This also may be due to varying water levels since the levels were reported- ly several feet lower than normal. Because of the size and depth of Great Slave Lake, it becomes icefree several weeks after small lakes on the mainland. In general, the phenology of the area was between 2 and 3 weeks behind that of the mainland. Undoubtedly, this has an important bearing on the species of birds that utilize the islands and on the chronology of their nesting. Although continuous observation would be necessary to determine comparative chronology of nesting of island versus mainland birds, there was less difference in nesting chronology than vegetation would imply. Our study was made on June 30 and July 3-5, 1968, and most species obviously were well into the nesting cycle and several were rearing young. Trauger photographed the West Mirage Islands on iVIay 29 when they were completely icebound. According to local observers, ice left Yellowknife Bay on June 22 which would not have allowed sufficient time for water birds to have reached the incubation stages we observed 10 days later. Krapu, how- ever, photographed the islands from the air on June 5. An examination of these photos showed a belt of open water along the edges of the islands that would have allowed water birds to swim and feed. As Preble (1908:98) noted, the vegetation of the islands of Great Slave Lake has the rugged, sparse appearance of the boreal forest-tundra ecotone rather than the boreal forest of the mainland near Yellowknife. Vegetation. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. O
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