Back on September 29, a boatload of birders clutching backpacks and sleeping bags headed out of Hyannis at dawn, bound for the continental shelf and its deep, warm water canyons some 130 miles to the south. This was an overnight pelagic trip run by the Brookline Bird Club, so they wouldn’t touch land again until the next evening. I’m sure they slept fitfully the night before, dreaming of obscure petrels and shearwaters, skuas, and maybe a tropicbird or some other exotic ocean wanderer – after all, they were paying for the chance to see mysterious and rare seabirds in these rarely birded offshore waters. And what they got, some 90 miles south of the nearest land, was hundreds of tiny migrating songbirds.
That’s right, way out there in the ocean, in the same spot they saw sperm whales and offshore bottlenose dolphins, these birders were treated to an incredible diversity of migrating songbirds, shorebirds, herons, and even bats and butterflies. This was the visible migration, or vis mig, I talked about last week, but in one of its rarest forms – actually seeing the over water, nocturnal migration of hundreds of birds bound for anywhere from the Caribbean to Argentina.
After dark on the 29th they drifted along the shelf edge at the head of Veatch Canyon, which plunges as deep as 14000 feet below the surface, though depths of 1400 feet are more typical along the canyon walls. Soon the group was hearing the faint flight calls of migrating warblers, and seeing their tiny, moth like shapes in the boat lights. A Blackburnian Warbler circled the boat, eventually landing and posing for photos. Someone heard a Scarlet Tanager flight call, then a Dickcissel, a bird of the central prairies that surely could have found more direct way to get to South America than via the open Atlantic off Nantucket.
At one point, an enterprising Pine Warbler took full advantage of the pit stop by hunting down a moth on the deck. At least two species of moth were recorded by the group, as well as a Mourning Cloak butterfly, which aren’t even supposed to migrate. More surprisingly, two different species of migratory bats came aboard, Eastern red haired and silver-haired. Both migrate south from eastern forests like birds and often end up crossing water – I once photographed one of several migrating silver-haired bats coming in off the ocean in Chatham mid-morning.
Between midnight and sunrise, those who stayed awake recorded 35 bird species, most of them terrestrial, circling the boat on their way south over the continental shelf. Most were confirmed with recordings and pixelated photos. Among them was a Connecticut Warbler, hard to find anywhere, that had come as far as 1000 miles already but was still 3700 miles from its final winter destination in Bolivia. A rare Prothonotory Warbler was photographed, amazingly the third one recorded on these offshore trips. An American Bittern, a heron of vast marshes, flew close enough for photographs and even demonstrated their seldom heard nocturnal flight call. The list of unexpected landbird migrants goes on – Peregrine Falcon, Green Heron, Cliff
Swallow, Wood-Pewee, Bobolink, Indigo Bunting. And an incredible 19 species of warblers, an enviable total for a day at the Beech forest in peak spring migration.
Oh yeah, they saw some cool seabirds too, like the state’s 8th record of the poorly known Barolo Shearwater – it was one of these trips only back in 2007 that documented the first US record of this enigmatic seabird of the Azores and Canaries. Throw in the 8 species of whales and dolphins, a few sea turtles and sharks, and fish like mahi mahi, yellowfin and skipjack tuna, and swordfish, and it’s clear the marine species showed pretty well too.
But I think it’s the up close and personal look at the trials of songbird migration that will define this trip for those who were there. You always remember the first time a Blackburnian Warbler lands on your hiking boot on the deck of a boat in the middle of the ocean.
