. The Canadian field-naturalist. 298 The Canadian Field-Naturalist Vol. 94. Figure 3. Generalized weather map showing high (H) and low (L) pressure systems, ridges (R) of high pressure, and fronts ( .^^ warm, -v^^ cold, ^»^^quasi-stationary). Numbered circles show approximate locations of Ottawa relative to weather systems at 07:00 during 23 April-11 May 1975 (1 = 23 April, 2 = 24 April, etc.) and the number of "goose echoes" during 04:00-14:00; O = very light or no migration (0-80 echoes, x = 25, N = 5), ® = light migration 81-160 echoes, x= 132, N = 5), 3 = moderate migration (161-
. The Canadian field-naturalist. 298 The Canadian Field-Naturalist Vol. 94. Figure 3. Generalized weather map showing high (H) and low (L) pressure systems, ridges (R) of high pressure, and fronts ( .^^ warm, -v^^ cold, ^»^^quasi-stationary). Numbered circles show approximate locations of Ottawa relative to weather systems at 07:00 during 23 April-11 May 1975 (1 = 23 April, 2 = 24 April, etc.) and the number of "goose echoes" during 04:00-14:00; O = very light or no migration (0-80 echoes, x = 25, N = 5), ® = light migration 81-160 echoes, x= 132, N = 5), 3 = moderate migration (161-240 echoes, x = 208, N = 2), •= heavy migration (> 240 echoes, x = 303, N = 4), and ® = number of echoes unknown. day (the number of "goose echoes" during 04:00- 14:00) is also indicated on the map, except for 23-25 April (days 1-3), for which radar data were incomplete. Visual observations suggested heavy migration on day I and very light or no migration on days 2 and 3. As Figure 3 shows, heavy and moderate migration occurred to the east of a low, under or near the west side of a ridge (days 1, 7 9, 19), near the center of a high (day 11), and far to the west of a low (day 16). Light and very light or no migration occurred to the west (days 3-6, 15) and east (days 2, 12) of a low, and to the east (days 17, 18), southeast (days 13, 14), and north (day 10) of a high. In other words, large numbers of geese often migrated with a light, warm, more-or-less southerly airflow, whereas few or no geese migrated with a cold, more-or-less northerly airflow. On the 2 d with calm, there was moderate migration (day 11) and very light to no migration (day 10). Our results are in good general agreerhent with the findings of many other studies that birds migrating north in spring usually move in largest numbers "in the central and western part of a high, the eastern part of a low, or an intervening transitional area" (see review by Richardson 1978). Three days (2, 1
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