Songbird Victims of 'Reverse Migration' Appear in Wake of Storm

Nov 1, 2017

 

Yellow-throated Warbler
Credit https://www.flickr.com/photos/pajarero/25924825660/sizes/l

We all have our travel nightmare stories. Missed and cancelled flights, luggage that ends up in a different continent, or being trapped in a sardine can of a plane stalled on the tarmac for hours. But imagine if you took off from Miami, heading to, say, Costa Rica for a long, warm winter’s retreat, only to find yourself landing right back in Boston?

That’s exactly what happened last week to a whole bunch of migrant songbirds. But for them, getting a new connecting flight won’t be so simple.


What happened last week is sometimes known as “reverse migration”, and Cornell’s BirdCast website provides a great explanation of the weather events that came together to bring these birds back north. When conditions are right, a group of birds attempting to migrate from the southeastern US to Central or South America could be lured into migrating by a passing cold front, only to end up caught in unfavorable winds offshore. The theory is that songbirds trapped in such winds would fly downwind to cover the most ground and hopefully reach land again. If those winds are southerly, this could bring them well north of their intended destination. Last week, and possibly again this week, the stage was set for such an event.

A bird list from Pochet Island in Orleans this past weekend provided some of the best evidence that reverse migration was afoot. Pochet, which you have to pronounce “Pochie” to prove you’re a local, is well known as a premier fall birding spot on Cape Cod. This isolated pocket of upland thickets, field, and forest is surrounded by saltmarsh, and lies just inland of the sandy treeless expanse of Nauset Beach. Pochet often collects interesting displaced birds. Several species that should be well south of Massachusetts by late October turned up there, including a Summer Tanager, Yellow-throated and White-eyed Vireos, a Cape May Warbler, Northern Parulas, an Eastern Wood-Pewee and a Yellow-billed Cuckoo. All of these were likely heading from Florida to South America when they got caught in southerly winds, and eventually deposited back off of New England, where they navigated back to shore.

 

Rough-legged Hawk
Credit Sean Williams

Birders on Nantucket and on Cuttyhunk Island turned up several more reverse migrants, including an Orchard Oriole, a species that leaves our area by mid-August, as well as multiple Yellow-throated Warblers and several other warbler species that should be in Central or South America by now. A Barnstable woman even had a possible Scarlet Tanager turn up on her deck. Who knows how many other of these tough-luck migrants are out there waiting to be found.

 

The question with these displaced birds is whether they will be able to successfully migrate again after the stress of being carried so far north against their will. It would be all but impossible to study this given the small number of birds involved, but if any of them turns up at one of the bird banding stations on Cape Cod, there is hope they will be captured again somewhere else, providing a clue.

 

A sharp counterpoint to these southern migrants was provided by the Rough-legged Hawk that showed up on the Cape this past weekend, like an emissary from an impending winter that still seems very far away. Usually a rare bird of true winter, we don’t typically see Rough-legs until December. This Arctic-nesting hawk seemed oddly out of place in the unseasonably warm fall weather, particularly among all the displaced southern species. Rough-legs were photographed on Friday at Pochet and at High Head in North Truro. They appeared to be the same individual, a gorgeous dark morph bird, whose dark-chocolate body and wing coverts contrast sharply with its silvery-white flight feathers. Another place to look for this lovely northern raptor if it’s still around is Sandy Neck in Barnstable. And while you’re looking for it, keep an eye out for some of those poor reverse migrants. They’ll be the ones on the side of the road holding signs that say “Costa Rica or Bust”.