Seabird sightings: surprises, spectacles, and perhaps a few avian records

During this reporting period on Leg I, we recorded 588 individuals of 22 species in the strip transect, comprising a diverse array of typical, and some not so typical, western North Atlantic seabirds. We sampled a wide variety of marine habitats, beginning in cool, foggy George’s Bank and ending in the hot humid Gulf Stream waters off Virginia. Not surprisingly, we recorded our highest species diversity of the cruise to date, as well as near-record totals for some species.

While tubenoses were the most abundant group, (with Wilson’s Storm Petrel and Sooty Shearwater again placing first and second in terms of abundance, respectively), we also tallied a few tardy migrant Red Phalaropes, a lingering Dovekie over the canyons along the southeastern edge of George’s Bank, and the occasional non-breeding Pomarine and Long-tailed Jaeger.

Our greatest surprises though came from the warmer waters to the south, particularly sightings of several species belonging to the intriguing genus Pterodroma—commonly known as “Gadfly Petrels”. The first noteworthy Pterodroma was a Fea’s Petrel (Pterodroma feae), seen near the mouth of Hudson Canyon, apparently a first record for this species in the New York Bight.

At-sea identification of this species based on current knowledge is very controversial. Fea’s Petrel is part of a larger complex of very similar species, formerly all lumped as subspecies under Soft-plumaged Petrel (Pterodroma mollis), which nests on islands in the south Atlantic and south Indian Oceans. Sightings of P. mollis in the north Atlantic have yet to be confirmed.

Meanwhile, Fea’s Petrel, breeding on the Cape Verde Islands, with a subspecies P. f. deserta—which also may be a distinct species—nesting on Desertas, Madeira Islands, and it’s close relative, Zino’s Petrel (Pterodroma madeira) are almost identical in size and plumage. Zino’s Petrel is critically endangered, with an estimated 65-80 pairs nesting on a few cliffs in the mountains of central Madeira. Separating Fea’s/Zino’s Petrel from Soft-plumaged Petrel is certainly possible, but separating Fea’s from Zino’s under at-sea conditions, where photographs and close range views of the diagnostic bill shape differences are difficult, if not impossible to obtain, is a monumental identification challenge!

Birds believed to be Fea’s have been photographed on commercial seabirding trips off Cape Hatteras, and there is a growing body of evidence based on geolocator tags suggesting that Zino’s remains in the east Atlantic during the non-breeding season and Fea’s Petrel, like Cory’s Shearwater, wanders west to the Gulf Stream off eastern North America when not at the breeding colonies. Unfortunately, photographing one of these birds from the NOAA Ship Henry B. Bigelow is practically impossible considering that sightings of these master fliers are usually brief and distant.

The other noteworthy Pterodroma sighting, without question the avian highlight thus far, was near near the southernmost point of our survey in 26°C indigo-blue waters of the Gulf Stream, about 330 kilometers (205 miles) east of Cape Charles, Virginia. Here, in water more than 4700 meters (15, 420 feet) deep , we encountered an impressive assemblage of Gadflies and other seabirds feeding over a school of mature Yellowfin Tuna. The group consisted of seven Trindade Petrels (running the gamut from dark to light morphs exhibited by this highly polymorphic taxon), one Fea’s Petrel, 20 Black-capped Petrels, and an assortment of other highly pelagic species including a Sooty Tern and a South Polar Skua, all taking advantage of small shoaling fish driven to the surface by the predatory tuna.

Trindade Petrel with dark morp

Trindade Petrel with dark morph, or plumage.

Seven Trindade Petrels apparently represent a new North American high count of this casual visitor from its namesake tropical south Atlantic breeding islands, and a first record of this species for Virginia; the Fea’s Petrel likewise is a first for these waters.

Part of the feeding flock estimated at more than 100 seabirds. The image just doesn't equal being there in person. (Credit: Richard Holt/NOAA)

Novel records aside, the spectacle of well over a hundred seabirds, some of them quite rare, or at least rarely encountered, wheeling and diving in a communal feeding frenzy was a sight not soon to be forgotten. (Unfortunately, the image above of part of the flock  just isn’t as captivating as seeing it in  real life.)  Needless to say, the seabird team was extremely grateful for the opportunity to make a small diversion from the trackline to investigate this avian spectacle.

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