Monday, July 2, 2012

Seabird and Whale Tales, 6/10/2012

On the morning of June 10th, a number of SSBC members participated in the NECWA sponsored pelagic trip out of Plymouth.  The weather conditions were ideal with relatively calm seas, sunny skies, and a gentle breeze.  Most years, the main destination for these trips is Stellwagen Bank, an underwater moraine about 20 miles offshore.   Stellwagen Bank is known to pelagic birders because it has several upwelling hot spots that force planktonic prey up to the surface where whales and, occasionally, large concentrations of seabirds may be found in the summer season.
Before departing from Plymouth Harbor, NECWA staff and guest naturalists discussed plans regarding the route that would most likely yield the greatest number of sightings – both avian and mammalian – in the eight hours that had been dedicated to the pursuit of marine wildlife.   Because there had been so few reports of seabirds and whales from Stellwagen Bank in the weeks leading up to the trip, the NECWA staff decided to make a run for an area 26 miles southeast of Chatham on Cape Cod.  Birds and whales had been reported in this area recently, so the plan was to get there as quickly as possible to maximize our time spent observing seabirds and other marine wildlife. 
The long ride to this area was well worth it since almost immediately after arriving at our destination the boat was surrounded by Sooty Shearwaters and incredible numbers of feeding Humpback Whales.   For most of the time we were in this area, there were 150 to 175 Sooty Shearwaters sitting on the water around the boat.   Occasionally, there would be a few Great Shearwaters in the mix and, on several occasions, we observed Manx Shearwaters buzzing by the boat.   We also had many opportunities to study Sooty Shearwaters in flight since they would sometimes lift off the water – en masse – to frantically pursue prey items driven to the surface by bubble feeding whales.  It was fun to watch a Sooty Shearwater seize a Sand Lance and fly off with it dangling from its mandibles.  Our group also heard the nighthawk-like vocalizations of the Sooty Shearwaters as they flapped and ran across the surface of the water to track down more feeding groups of whales.   Northern Gannets were also observed along the back side of the Cape and in the area where all of the whales and shearwaters were feeding.  While not particularly numerous on this trip, birders on board had a number of opportunities to observe Wilson’s Storm-Petrels, a swallow-sized seabird that breeds on the Antarctic coast.
Whale watchers were not disappointed with the decision to go southeast of Chatham.  Many of the Humpback Whales were exhibiting a number of interesting behaviors including: flipper flapping, lob-tailing, breaching, and, as mentioned earlier, frequent bubble feeding.  NECWA  staff estimated that there were as many as 80 Humpback Whales in the area with all of the seabird activity.  Many images of the whales were obtained by NECWA staff and interns.  A good number of these whales were identifiable by looking at the fluke pattern images that had been obtained.    In addition to the Humpback Whales, there were occasional appearances made by Minke Whales.   Also noteworthy was a large group of Gray Seals hauled out on the beach in Truro.   
Another highlight of the trip was a Pomarine Jaeger that followed the boat closely for several minutes much to the delight of all on board (see David Clapp’s image).   The jaeger show also included two Parasitic Jaegers harassing terns in the rips just offshore from Provincetown.
Lastly, the birders on board were surprised to see two breeding plumaged Razorbills just offshore from Provincetown on the return trip to Plymouth Harbor.

Sooty Shearwater                      (2000)
Great Shearwater                      (30)
Manx Shearwater                      (4)
Northern Gannet                       (41)
Parasitic Jaeger                          (2)
Pomarine Jaeger                        (2)
Wilson’s Storm-Petrel               (46)
Common Loon                           (10)
Herring Gull                                
Great Black-backed Gull
Common Tern
Razorbill                                      (2)

*Many thanks to David Clapp for providing these great photos!

Jim Sweeney

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