Point Pelee National Park of Canada
Bird Numbers at Point Pelee Arrival of Migrants
The total number of bird species recorded at Point Pelee is 372, of which at least 340 of these species have been recorded during the spring migration period. The stream of birds in the spring is not a steady flow from the south. The birds usually arrive in intermittent waves, a pattern unique to eastern North America. In some years these are well marked but, in others the fluctuations in numbers and variety is so meagre that a wave in difficult to detect. A "wave" occurs as a result of a warm weather front advancing from the south or southeast meeting a cold weather front from the north or northwest. Two situations will cause the birds to descend. One is when the two fronts meet at ground level. The other is when a warm front in which migrating birds are flying overrides a cold front. The rising warm air becomes cooler with the increasing altitude until it is finally too cold for the birds and they descend.
If these nocturnal (night-time) migrants find themselves over Lake Erie near sunrise they must continue onwards or drown. After flying perhaps hundreds of kilometres in one night, it is this extra 30 to 40 kilometres across the lake that really demands their last strength. This explains why exhausted birds are sometimes found at the tip of the Point. A similar situation, but on a larger scale, occurs when migrants cross the 800 to 1000 kilometres of the Gulf of Mexico. If the weather is good they continue inland in one continuous flight without stopping, but with a north wind and rain they descend on the coast in great numbers, often in an exhausted state.
What everyone hopes for in the spring is a major wave with a "grounding" of migrants. An incredible grounding of migrants occurred on May 9 to 12, 1952.
Estimates of some of the birds present included 1 000 black-and-white warblers and 20 000 white-throated sparrows. Another occurred on when 3 000 northern orioles were engaged in visible reverse migration off the Tip, while the day's tally for chimney swifts was 900. On May 15, 1978, in just the Tip area of the park, there were 80 yellow-billed cuckoos, 70 eastern wood-pewees, 250 scarlet tanagers and much more.
Other "big days" for certain species are tundra swan (2500), red-breasted merganser (100 000), whimbrel (500), northern flicker (250), bank swallow (12 000), white-eyed vireo (50), hooded warbler (18) and kentucky warbler (13).