. The Canadian field-naturalist. 276 The Canadian Field-Naturalist Vol. 89 29 October, and the last major departure(s) took place between 5 November and 15 No- vember. Thus, there was good general agree- ment between departure dates in 1971 and in the two following years. 3. Weather Conditions during the Main Departures On 30 and 31 October the center of a high- pressure system moved from the southern tip of James Bay in an easterly direction across northern Quebec. The synoptic weather situa- tion at 1300 hours on 30 October is shown in Figure 4a. At Quebec City on that day temperatures were
. The Canadian field-naturalist. 276 The Canadian Field-Naturalist Vol. 89 29 October, and the last major departure(s) took place between 5 November and 15 No- vember. Thus, there was good general agree- ment between departure dates in 1971 and in the two following years. 3. Weather Conditions during the Main Departures On 30 and 31 October the center of a high- pressure system moved from the southern tip of James Bay in an easterly direction across northern Quebec. The synoptic weather situa- tion at 1300 hours on 30 October is shown in Figure 4a. At Quebec City on that day temperatures were above freezing, cloudiness varied, and there was no precipitation. The direction of the surface wind varied betwoen northeast and east all day on 30 October and well into 31 October. On 30 October the wind at about 5000 ft (1520 m) above sea-level (as determined from the 850 mB maps) was from the west in the early morning. By mid- day it was about northwest and at 1900 hours it was due north (at about 25 knots or 46 km/h). Average directions of the "goose echoes" on 30 and 31 October varied from about 210° to 220°, a course almost directly towards the wintering grounds near the Atlantic Ocean. We do not know at what height the birds were migrating but somewhere between surface and 5000 ft (1520m) they would have encoun- tered a tailwind and it is not unlikely that the climbing geese levelled off at that altitude in order to make use of those favorable wind conditions. The first period of major departures ended in the early morning of 31 October. It is unknown at what time the wind at 5000 ft (1520 m) changed from north (on 30 Octo- ber, 1900 hours) to south-southwest (on 31 October, 0700 hours) but it is probable that the shift coincided with the end of the first major departure (0200-0400 hours on 31 October). On 8 November the Quebec City region was sandwiched between a large high, centered south of the Great Lakes and a trough of low pressure extending between La
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