May 28, 2018 will be a day that will go down in birding history. It was the day that the largest sheer number of warblers was ever seen at one location in one day. Even a non-birder should be impressed by the numbers—an estimated 721,620 warblers that passed by a set of observers during what had to be an unforgettable nine hours. They were in Quebec along the north shore of the St. Lawrence at the Tadoussac Dunes, a three-hour drive northeast from Quebec City and a location famous for its fabulous whale watching.

We have felt fortunate to have been on Monhegan Island a few times when thousands of migrating birds, largely warblers, descended on the island under unusual weather conditions. One May day in particular has always stood out, when brightly colored warblers seemed to literally be everywhere on the island. We have always remembered one particular image from that day: an impossibly brilliant orange-throated blackburnian warbler hopping at our feet on the dark rockweed at Lobster Cove searching for food. Normally a view of this species requires craning your neck to see its tiny form high above you in the top of a towering spruce tree. (This one was probably too exhausted from its long nocturnal flight to be concerned too much about anything except finding food.) There were certainly hundreds, probably thousands, of warblers on the island that day. Other birders have recorded some of the highest counts of warblers ever in Maine on Monhegan Island—counts usually in the hundreds at best.

Over on Machias Seal Island, lightkeeper and birder Ralph Eldridge once estimated 1,000 magnolia warblers and 100 blackburnian warblers during an unusual fallout on June 6, 2006, that included thousands of birds in total. Down at Sandy Point in Yarmouth, Derek Lovitch has had incredible morning flights in the fall where he tallies thousands of warblers and hundreds of other songbirds. In September of 2017, he once counted more than 8,000 birds passing by in just a few hours.

Any of these Maine high count days would have been incredible to witness. But the numbers pale in comparison to the more than 700,000 seen by those amazingly fortunate observers at Tadoussac!

The warbler species that they counted in such immense numbers were mostly birds whose primary breeding range is to the north and west of southern Quebec—birds like bay-breasted, Cape May, magnolia, Canada, and Tennessee warblers among others. Most birders never see more than a handful of bay-breasted warblers each migration. We, for example, this spring only heard a few going through in migration and never set eyes on a single one. Last year we probably saw fewer than 10 during both spring and fall migration here in Maine. In fact, the highest number reported for Maine in the eBird database was 40 counted by birding legend Peter Vickery on the breeding grounds many years ago in northern Maine.

On that amazing Tadoussac big flight day just a little over a week ago, the observers estimated 144,300 bay-breasted warblers passed over and by them in those nine hours! At some times during the day they could count up to 300 in a single scan! In fact, they may have witnessed almost 2% of the entire world population of bay-breasted warblers passing by them on that historic day!

It may be tempting to think that such an unprecedented number of birds signals something about the status of their populations. But no, this event was a massive migration spectacle caused by an unusual set of weather conditions—conditions that birds must deal with every migratory period and that highlight just how difficult and perilous their migratory journeys really are.

Another reason why this event was so historic was because of the people involved in documenting it. Many birders might have seen large numbers of birds and marveled at it but few would have attempted to devise a way to estimate the number of birds passing through. Not only that but these birders happened to also be very skilled at the difficult feat of identifying tiny warblers in flight. And they stayed there the entire day continuing to count and estimate and photograph and videotape a migratory movement the likes of which had never been documented.

Let us hope that conservation efforts will ensure that such an abundance of birds as passed by Tadoussac will be around for future generations of bird lovers to have a chance to witness migration spectacles that leave us all breathless with wonder.

Jeffrey V. Wells, Ph.D., is a Fellow of the Cornell Lab of Ornithology. Dr. Wells is one of the nation's leading bird experts and conservation biologists and author of “Birder’s Conservation Handbook”. His grandfather, the late John Chase, was a columnist for the Boothbay Register for many years. Allison Childs Wells, formerly of the Cornell Lab of Ornithology, is a senior director at the Natural Resources Council of Maine, a nonprofit membership organization working statewide to protect the nature of Maine. Both are widely published natural history writers and are the authors of the book, “Maine’s Favorite Birds” and the newly published “Birds of Aruba, Bonaire, and Curaçao” from Cornell Press.