Migration Fallout!!!! in the Florida Keys

End 2010 I started working with the USFWS to design a monitoring protocol for the federally endangered Miami Blue butterfly. This butterfly was historically restricted to the coastal areas of southern Florida, but through habitat loss its range has declined so much that it was considered extinct for a few years, until USFWS personnel discovered an isolated population on the Marquesas Keys, part of the Key West National Wildlife Refuge and situated 15km west of Key West. One of the perks of developing this monitoring protocol was regular trips to Key West. Hard life, I know :) Anyway, one of these trips happened during mid October 2011. Frustratingly, I wasn’t able to get to the Marquesas during my week-long visit to the area – the sea was just too rough for the 15km flats-boat ride. Being stuck on the mainland during a storm during migration season however had one massive advantage! MIGRATION FALLOUT!


Migration fallouts occur when frontal systems develop during migration periods. During this time, strong, turbulent winds and rain prevent migratory birds from traveling between their summer and winter grounds. These migratory birds are then forced to seek shelter until weather conditions calm down. These migration fallouts are particularly pronounced in coastal areas where the migratory birds leave land to cross the ocean. Which is why the migration fallout in the Keys was one mind-blowing experience. During 2011, the frontal system over the Keys stalled for several days, bringing an incredible feast to birders willing to tolerate the never-ending rain and winds which brought the southbound migration to a standstill.


Because I was somewhat stranded for a number of days, unable to do the work I set out to do, I had quite a bit of free time to experience the migration fallout. Most of this time was spent at the Fort Zachary Taylor State Park in Key West, where I headed after assessing the ocean conditions at Key West. During this time, the part did not disappoint. Really, words cannot express experiencing thousands of warblers, thrushes, and other neotropical migrants visible from every corner of the park. In fact, two trips to the state park, on Oct 17 and Oct 19, yielded a total of 19 species of neotropical warblers. Also noteworthy was three species of thrush (Grey-cheeked, Swainson’s, Wood) under one tree.

Ft. Zach wasn’t the only place where I saw warblers, with the USFWS boat yard adding Blackburnian Warbler, the Key West Botanical Garden adding Yellow-throated Warbler and Black-throated Blue-Warbler, and a trip to the Key West National Wildlife Refuge (actually just before the storm arrived) producing Yellow Warbler (Mangrove Warbler, actually), Prairie Warbler, and Northern Waterthrush.

During this entire time, raptors also didn’t fail to impress. Perhaps the best spot for raptor watching turned out to be the Florida Keys Hawkwatch site, where near record numbers of Osprey, Peregrine, Swainson’s Hawk, Merlin, Mississippi Kite, American Kestrel, Sharp-shinned Hawk, Cooper’s Hawk, Broad-winged Hawk, and record numbers of Northern Harrier, Red-shouldered Hawk, Broad-tailed Hawk and Swallow-tailed Kites were observed. Though the abundances at Ft. Zach wasn’t so high as  at the Hawkwatch site, the consistent flow of raptors overhead was still worthy of appreciation, with regular Northern Harriers, Peregrines, Broad-winged Hawks, Red-shouldered Hawk, Cooper’s Hawk, Merlin, and American Kestrel.  One particularly impressive moment was when a Broad-winged Hawk caught a Yellow-billed Cuckoo – quite the fright since it took a while to register what exactly was going on mere meters in front of my eyes.

One of the more impressive sights, perhaps one of the most impressive during my birding life, was a flock of Broad-winged Hawks we saw at the Key West National Wildlife Refuge. On Oct 13, a flock of Broad-wings (with a few scattered Swainson’s and Red-tailed Hawks) came in from Key West’s side and started circling above our heads at the furthest western end of the Marquesas. While we looked at this flock, a steady stream of Broad-wings joined this flock from the Dry Tortugas’ end, joining the flock overhead. The process was going on for a few minutes. Without the necessary experience in counting raptors, I found it very hard to estimate the size of the flock. My own feeling was that there was over 1500 birds in the flock, the USFWS ecologist with me estimated 1800, while my graduate advisor Nick Haddad guessed that the number would be closer to the higher estimate. Was this the biggest raptor congregation ever seen in the USA?


Above: Part of the circling raptors (left) and the constant stream of raptors joining them from the right (Tortugas’ end). That stream of raptors from Tortugas stretched as far as the eye could see!!!

While the migrants certainly dominated the show, I also had some awesome views of more resident species during October 2011. Perhaps one of my favorites was a very cooperative Yellow-crowned Night-heron at Bahia Honda State Park, while a couple of Red Knots were also welcome additions to the trip list. And who will ever get tired of the graceful Magnificent Frigatebirds patrolling the skies of the Florida Keys.

Of course I also had a little bit of time for rarity chasing. One of the rarities that really kind of came looking for me was an awesome male Masked Duck, at the Key West Botanical Gardens, while I ended my trip with a cracker in the form of a Kirtland’s Warbler, at Richardson’s Park in Ft Lauderdale. And how awesome, spending about 3 hours with the bird all by myself before the pack of other twitchers arrived. I even managed to take a few cracker shots of the awesome rare bird on its way to the Bahamas, and truly the last warbler I expected to see on this trip. Oh yes, we also picked up another regional rarity, a Bell’s Vireo, fluttering about quite close to the Kirtland’s Warbler at times. Other birds spotted at Richardson’s Park included Yellow-billed CuckooWhite-eyed VireoYellow-throated Vireo, and Red-eyed Vireo (someone else spotted a Philadelphia Vireo, but I never laid eyes on it), as well as OvenbirdCape May WarblerNorthern Parula, and Black-throated Blue-warbler.

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