Pelagic birding in the Gulf of Mexico: Mississippi Canyon in September
Last weekend, I joined 18 other birders from Louisiana and Mississippi on pelagic trip from Venice, La., organized by Justin and Devin Bosler. Our destination was the Mississippi Canyon, a deep gash in the continental shelf edge about 40 miles south of Grand Isle, La.
Pelagic birding in the Gulf of Mexico is famously less productive than off our Pacific and Atlantic coasts. However, the Mississippi River Delta’s long, finger-like projections out across the continental shelf and the deep underwater Mississippi Canyon lie close enough together to offer day-tripping birders one of the best shots at true deep-water pelagic birds anywhere on the northern gulf.
Sure enough, about three and a half hours after an early-morning departure from Venice, we had reached deep blue water at the edge of the canyon and there came upon our first tubenose of the day: a Cory’s Shearwater (Calonectris diomedea). Cory’s Shearwater is a large shearwater (in fact, its species name refers to albatrosses) that breeds on islands in the Mediterranean Sea and North Atlantic Ocean.
We were trying to see and photograph the underside of this bird’s primaries to try to see whether it looked like an Atlantic or Mediterranean bird, but it never got far enough off the water to offer a glimpse. Both subspecies have been documented in the Gulf of Mexico. This individual is in molt; note worn, brownish outer primaries and the crisper, grayer inner primaries growing in. It’s molting secondaries too. Birds like this are thought to be immature birds too young to breed that wander the oceans until they are sexually mature.
Our second shearwater of the day was an unfortunate Audubon’s Shearwater (Puffinus lherminieri) that was under attack by several Magnificent Frigatebirds (Fregata magnificens).
The shearwater kept diving underwater in an apparent attempt to escape the frigatebirds’ relentless pursuit.
This shot shows the dark undertail coverts and relatively long rectrices that separate Audubon’s Shearwater from the much rarer (in these waters) Manx Shearwater.
In the slow, sunny hours between bird sightings, other marine life kept us intrigued — especially the flying fish. These extraordinary fish launch themselves from the water into the air and beat their lower caudal (tail) fins rapidly across the surface of the water to provide thrust while spreading their huge pectoral and pelvic fins, which create lift and allow the fish to soar for several hundred feet across the surface of the water.
Jellyfish, sea turtles, a shark, and cetaceans also caught our attention. You can see a video clip of bowriding bottlenose dolphins on my Facebook page.
We encountered a few pelagic Bridled Terns (Onychoprion anaethetus), including one group of about 15 birds that were calling back and forth.
We were rarely out of sight of Magnificent Frigatebirds — which is fine by me!
As we left deep water, we arrived at a long line of floating wrack and sargassum, which brings with it an entire ecosystem of fish, sea turtles, and yes, birds. Black Terns (Chlidonias niger) swarmed over schools of fish. Black Terns were absent over the blue water, replaced by Bridled Terns, but over the continental shelf and along the sargassum line, they were present by the thousands.
Frigatebirds don’t harass only smaller birds; they go after each other as well. This young bird had what looked like an eel, and a nearby adult female wanted it.
Her dive forced the young bird to drop its prey.
Ahhh. But good luck keeping it.
On the rock jetties at the mouth of Tiger Pass, an entrance into the Mississippi River, we had a couple of Lesser Black-backed Gulls among Herring Gulls and large numbers of Laughing Gulls and Brown Pelicans.
You can also check out Erik Johnson’s account of the day, and I’ll be doing a second post about a certain young jaeger we encountered.
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Very cool!
Some very nice photos there! I esp. loved the zig-zagging flying fish.
What an exciting trip!