From personal experience in being involved in the canola pollination industry, I'll say that we move bees and have heavy stocking rates compared to a honey production scenario. Frankly, we want to get them in and out as quickly as possible, because in southern Alberta when the canola is in bloom the bees do well, but once the canola starts shutting down, there is nothing else out there but prairie grass.
Unless they are along a river valley or something, where there is some natural vegetation and some diversity, they can go downhill if they're out in the prairie. There are large populations at that time of the year, and they need an abundant food source. If they're not able to get that they can go down quickly, so we try to get them out as soon as we can in those situations. There are definitely regional differences, so I don't want to speak for those across the country, but in that situation we do know that it can lead to poor fall nutrition, which will lead to higher winter losses.