In late March, mallard, American black duck, pintail, redhead, canvasback and killdeer are present in their greatest numbers. Usually once or twice during the month, however, a warm spell will occur, and it is then that there will be a wave of migrants including the first insectivorous species. With an exceptional warm front in the last few days of April a surge of typical May migrants may appear. Now many of the long-distance, land bird migrants arrive, many from Central and South America. It is interesting that these migrants from afar arrive on more predictable dates each year than do those spending the winter closer to Ontario.
Weather plays an important role in the numbers of a species one is likely to see.
This phenomena, however, is the exception, rather than the rule. Most of the waterfowl migration is over by early to mid-May and many of the April land bird migrants as well have already passed through. Towards the end of May, red knot, one of the latest migrants, will arrive and at this time several other shorebirds are found in great numbers. JUNE June, the time for peak nesting activity of many species, is also when we see spring migration cease entirely. However, prior to June 15 migration is still noticeable but it is a time needing much more field work to establish late departure dates of many species.