It has now been three weeks since fall migration monitoring at the Cabot Head Research Station began, but it still feels like summer, both in terms of temperatures and birdlife. Suffice it to say, evidence of migration has been sparse here. We’ve had very few migrants, either in our nets or in the trees. The total number of banded birds in these first three weeks is the second lowest in 15 years. It seems that the local birds were not very abundant, possibly a result of the drought-like conditions of the summer.
At this time of year, an American Redstart, for example, captured in our nets could be a local bird not yet intent on migrating or a bird coming from further north, already in migration mode. It is not always possible to distinguish between the two at the start of the migration season. However, some species do not breed on the Bruce Peninsula and their arrival certainly heralds the beginning of migration. This is true, for example, for Wilson’s Warblers. Two of them were detected for the first time on August 22. Other denizens of the boreal forest have also started to turn up on our shores: the first Bay-breasted Warblers were seen on August 27; first Blackpoll Warbler on August 30; the first Tennessee Warbler on September 1st; two Philadelphia Vireos were captured on September 5, the first of the season as well.
That said, migration is indeed happening, even though it has begun in a subtle and subdued way. Yet sometimes it feels like it is not. It all depends on the right condition. On September 5, for example, there was a strong south wind, bringing warm and humid air to the northern Bruce Peninsula. It was also pushing the thermal-riding, soaring-adept Broad-winged Hawks towards Georgian Bay. These Buteos, like all soaring raptors, do not like being over big bodies of water, where no thermals develop and where it is difficult for them to ride the sky effortlessly. So, this south wind was pushing and concentrating the Broad-winged Hawks along the shoreline, as they tried to fight against it. And this is how we witnessed a congregation of about 200 of them, milling together in a massive “kettle” (as the hawkwatch jargon describes them). It was an impressive sight, made even more interesting by the odd presence – among all these raptors – of a lone Common Nighthawk! Which, despite its name, is not a raptor and does usually not migrate in the middle of the day. But the natural world is never afraid of bending the textbook rules!