Monday, December 2, 2019

Black-capped Petrels to the North - by Kate Sutherland

This past August I was hired as the seabird observer for a NOAA beaked whale cruise.  The platform was the R/V Hugh R. Sharp owned and operated by the University of Delaware and the project was Atlantic Marine Assessment Program for Protected Species: Integrated Technologies for Deep Diver Ecology Project (ITS.DEEP 2019) headed by Chief Scientist Dr. Danielle Cholewiak of the NOAA Northeast Fisheries Science Center in Woods Hole, MA.  This meant that in addition to surveying for seabirds in a new location far north of my usual haunts, I would also get to see some really cool species of beaked whale and other cetaceans more commonly encountered far from shore.  And while beaked whales are the specialty of others aboard the ship, seabirds happen to be mine.  As it turns out, we headed offshore into another one of my specialties, the Gulf Stream!

I was not sure what to expect offshore from Massachusetts, but had some idea what had been seen on previous cruises up there and also had been on at least two pelagic trips that covered some of the canyons offshore.  We also had recently helped American Bird Conservancy and partners capture and fit ten Black-capped Petrels with satellite transmitters that we had been watching more or less live for months.  A number of the white faced birds had ridden the wind right up to the shelf break south of George's Bank.  One was even documented in one of the areas that we transited earlier in the month!
Many of the dark faced birds were foraging to the east of Cape Hatteras, way offshore.  In 2008 Steve Howell and Brian Patteson wrote about the possibility that these two types of Black-capped Petrel use different areas to forage, breed on a slightly different schedule, and also perhaps have different nesting locations.  We have learned a lot more about how to differentiate these two types at sea and also more about the nesting locations of the dark faced birds.  Until October of this year, we had no idea that a white faced bird might be nesting on Hispaniola, but one of the tagged individuals was recorded over and around the island.
The timing is earlier than that of the dark faced birds, so this one individual does support that part of the narrative.  It did not, however, lead us to a new and unknown nesting location.  But this is just one bird, we don't even know for certain that it is a breeding individual, but we do know that petrels in the genus Pterodroma exhibit philopatry, or the tendency to return to the island or locale from which they fledge.

Back to Massachusetts.  Black-capped Petrels have certainly been seen offshore up there, but rarely more than one or two.  Photographs of individuals have all been the white faced type.  There have also been Black-capped Petrels recorded in the Western Palearctic, majority white faced but dark faced and intermediate birds have been recorded as well.  On this NOAA survey in August, over a ten day period near and offshore of the Continental Shelf, Skye Haas and I recorded exactly 50 Black-capped Petrels.  A number of these were easily identified as white faced birds (photo by Kate Sutherland),
but there were also some that looked more intermediate, and I did photograph at least two dark faced birds.  This is interesting for a number of reasons.  Number one, that's a lot of Black-capped Petrels!  How could there be so many up there, yet trips in some of the same areas using chum do not encounter similar numbers?  Perhaps it had more to do with the conditions that were in the area we transited.  The water on and offshore of the shelf break was up to 28 degrees C and moving around three or four knots.  It also looked like Gulf Stream water, gorgeous blue, full of Band-rumped Storm-Petrels, Audubon's Shearwaters, and of course Sargassum.  So is it possible that these birds are using the areas where the Gulf Stream moves offshore to the northeast and we were just lucky that those waters happened to be where we were?  Or are they always up there, feeding in the canyons and around the seamounts, and it just happens that they are too far to be attracted to the birding trips that are only out for a night or two farther to the west than we were on the research vessel?  Who knows, but it is certainly worth noting that they were there!  Also makes me wish that someone was out there surveying more often, but right now, we'll take the transmitters and the occasional trips out to that area!

Our trip from Hatteras October 18th turned up nice numbers of Black-capped Petrels, various types, but many intermediate birds, only maybe one or two white faced birds, and a handful of nice, dark faced birds.  I know I write this again and again, but Black-capped Petrels are incredible birds, oceanic superheroes, that are likely facing many threats not only where they nest, but also at sea.  Stay tuned for the next chapters in the saga.  And check out some of the sites below that have information about what is being done to protect these birds at sea and on Hispaniola.  I hope to be out there again next year to see what Black-capped Petrels look like offshore of Massachusetts in the summer of 2020!

Birds Caribbean has a working group specific to Black-capped Petrels:

American Bird Conservancy spearheaded the transmitter project:

Along with Atlantic Seabirds:
They are also partnered with USGS South Carolina Cooperative Research Unit & Clemson University

Groupo Jaragua is based in the Dominican Republic:

A few more images of Black-capped Petrels from the R/V Hugh R. Sharp.  First two birds in one frame on August 24, 2019, which was notable!  We saw multiple Black-capped Petrels together on a few occasions.  Then two record shots of one of the dark faced individuals we saw, this one from August 21, 2019.  Photos by Kate Sutherland.