This is the report for the August 16, 2020 Buena Vista Audubon pelagic trip.
Twenty-seven passengers and two leaders met at Seaforth Landing in Mission Bay for our 7:00 AM departure. Seaforth is not a new location for pelagic trips, as this is the location for the San Diego Audubon Bird Festival trips each winter, but it is a new dock for our trips. Check in and orientation were all done with appropriate social distancing and seemed to go smoothly, with facemasks were worn by all.
The 80 ft. Legacy is a new boat for us, and unlike all other local pelagic birding charters we have used, is not a fishing boat. The Legacy was built in Washington State as a tour-type boat and is now used mainly for whale watching. Like anything new, this boat presents some challenges, but the positives aspects include abundant seating; a large salon area out of the weather with large windows; a speed of 11-12 knots compared to the usual 8.5 kts; and better visibility and space for the group leader on the intercom. Best of all, there is no competition with fishing charters for trip scheduling.
We loaded-up and departed to check out the Mission Bay bait receivers just beyond the docks, where we found the usual suspects, such as pelicans, cormorants, herons, egrets, and gulls. Departing the bay’s jetty was smooth, although a last minute change to the forecast gave us a southwest breeze that increased during the day, giving us a crosshatched sea surface that made the ride less comfortable than we’d expected. Nothing serious, but we get spoiled with nice seas so much of the time. This also made finding small alcids on the surface tough before we drove over them.
The first “seabird” offshore was a group of Red-necked Phalaropes along the scum line from the tide change this morning. The first few were followed by a half dozen more, then by more and more extending off into the distance. Red-necked Phalaropes are early returnees from subarctic breeding areas. They spend the majority of their lives at sea picking plankton from the surface. They pass through here in the fall and are largely south of us by early winter. We also had a few Red Phalaropes today, generally a little farther offshore than the Red-necked. Red Phalaropes breed higher in the arctic and arrive in numbers later in migration. Most years a few winter locally. The next seabird seen was Black-vented Shearwater. These guys are our local shearwater. They are most abundant in the near-shore waters, but a few scattered birds can be found well out into the California Bight. Black-vented Shearwaters breed on a few islands off the west coast of Baja California. Post breeding dispersal is into our area and as far north as Point Conception. Their numbers will increase into fall and winter, when they often become abundant, and are often seen in large numbers from shore. Mass feeding concentrations are occasionally seen that may range into the tens of thousands. They were the most common seabird we saw offshore today.
We arrived at the north end of the Nine Mile Bank to find a little more life. As we moved off into the deep-water side of the bank, we found a mix of Pink-footed, Sooty, and Black-vented Shearwaters. Pink-footed and Sooty Shearwaters are wanderers from the southern hemisphere. Actually, wanderer is the wrong word as they come here with purpose: They feed, fatten, and molt here, then return south to breed in the southern hemisphere summer. Pink-footed Shearwaters are from the Juan Fernandez Islands off Chile, while Sooty Shearwaters breed on a number islands off Australia, New Zealand, and South America. Some of these Sooties may have the animal world’s longest annual migration, as shown by some satellite-tagged birds that have done a figure eight transit of the entire Pacific Ocean. Pink-footed Shearwaters increase here in the summer and fall before returning south. Sooty Shearwaters pass through here in their biggest number in spring then decline into fall.
Our trip took then us out across the San Diego Trough. This is a ten-mile wide, 3500 ft. deep, trough that runs mainly northwest to southeast. The bottom here is flat and featureless, which often makes it the quietest portion of the trip, but once in a while it will turn up some interesting birds. Today it provided our only look at Sabine’s Gulls. These are beautifully patterned black, white, and gray gulls that live in a world of rather dull brown and gray seabirds. Sabine’s Gulls breed in the high Arctic and those migrating down the west coast of North America spend the winter off the west coast of South America. We also got a good look at a Pomarine Jaeger that was sitting among a group of resting Pink-footed Shearwaters. Pomarine Jaegers are also Arctic breeders. “Poms” as they are often called, are our most common jaeger in the offshore waters. We sometimes get large numbers of them during migration and usually have a few stay for the winter. They are quite capable of catching their own food but prefer to pirate their food from terns, small gulls, and shearwaters.
Crossing the Trough we arrived at the edge of the Thirty Mile Bank, a two thousand foot rise from the floor of the trough, with a few spots along the ridge rising to within 750 feet of the surface. There were a fair number of storm-petrels here, including three of our expected storm-petrel species. The large, big-winged, short tailed, and all dark Black Storm-Petrels breed on our local islands off Baja California. Black Storm-Petrels are far and away the most numerous storm-petrels, ranging from the inshore waters out to perhaps 60 miles or so. A few Black Storm-Petrels were seen today as close as the inside of the Nine Mile Bank. Next seen were a few Leach’s Storm-Petrels. Most of these were the chapmani subspecies of Leach’s. The white rump patch is highly variable from bird to bird. A white smudge on the sides of the rump is the most common pattern, but it can range from all dark to bright white, usually divided by a dark strip down the middle of the rump. These birds have a rather dark brown body, long narrow wings, and a medium-length forked tail. They are smaller than the Black Storm-Petrels and have a manic, rapid, zig-zaggy flight compared to the more relaxed flight of a Black Storm-Petrel.
The last of the three regular storm-petrels today was the Ashy Storm-Petrel. This is a brownish storm-petrel, with a shorter wing and a long tail that may show a buffy rump patch. The under-wing coverts are a light gray. Ashy’s fight style is fast and rather direct, with a shallow wing beat. They are smaller than Black Storm-Petrels and a little less boat friendly. Generally we see more Leach’s Storm-Petrels in the late summer and fall, and more Ashy Storm-Petrels in the spring and early summer. Black Storm-Petrels are here from late winter until early November.
Then, just to liven things up a bit, we had a Least Storm-Petrel as we worked our way up the bank later in the day. This is a Mexican species that barely makes it into California’s waters. We got a very nice, though rather brief, look at it. Least Storm-Petrels are tiny, all dark, “big” winged, and short-tailed, sometimes looking like they have no tail as they move rapidly away with a steady deep wing beats. We search for these each year and sometimes miss them or see very few. Then, in other years, we may see very large numbers on the Thirty Mile Bank. Least Storm-Petrels associate regularly with Black Storm Petrels, less so with our other two species of storm-petrel.
While we were sorting through the storm-petrels, Paul Lehman called out an Arctic Tern over the PA system, close in at 11 o’clock. It turned out there were actually two adults – great birds for San Diego waters. Arctic Terns are another northern breeder and much of the western population passes well off our shore, often out over the shelf edge some 150 miles to our west. Few make it into the Southern California Bight, which makes them a tough bird to get in San Diego waters.
We drove over the high part of the Thirty Mile bank and into the “Corner”. This area is the spot where the border between the United States and Mexico makes a radical left hand (southerly) turn. This is also the spot where San Diego County and Los Angeles meet. In the old days, once you were three nautical miles from shore you were in international waters. Then, in 1982, that changed to a 12 nm contiguous zone and a 200 nm economic zone. This led to a change in the international and County borders offshore: between Point Loma and the Coronado Islands; between the Coronado Islands and San Clemente Island; and finally between San Clemente Island and Guadalupe Island. The end result was this sharp bend in the border and the creation of the area we now call The Corner. It also meant that San Clemente Island was in LA County, with the County line half way between the Island and San Diego. Complicated? Yes. Anyway, we found two more terns on a floating patch of kelp. These were LA County Common Terns. In spite of the name, they are not all that common. Care must be taken distinguishing Common Terns from the very similar Arctic Tern. A complete treatise on the difference is best left to the field guides, but I find that the easiest feature to start with is the underwing, which shows a smudgy black trailing edge to the primaries in Common Terns, and a very thin and neat black edge on in Arctic Terns. Common Terns often show a dark wedge in the upper primaries as well, where the Arctic does not. Overly simple, but useful. We did get some additional Common Terns back in San Diego county later in the day.
We also had a bit of a surprise with a flyby Pelagic Cormorant out here in no-man’s-land. In spite of the name, Pelagic Cormorants are not at all pelagic. They are usually found close to shore, and along rocky coasts. Like all cormorants, they must return to land to dry their feathers, otherwise they can become waterlogged, unable to fly, and will sink if they sit on the sea surface for too long. So what’s it doing out here at the Thirty Mile Bank? Our best guess is that it was transiting between Islands in the Southern California Bight.
We jogged back and forth up the bank for a nice look at a couple of Red Phalaropes, then stumbled on a pair of Craveri’s Murrelets, which flushed ahead of us. Craveri’s Murrelets are another Mexican species that most years just make it into Southern California waters. Some years they are absent, others years they move north of us. Paul worked to get us back on these guys, but the crosshatched wind wave and swell made it difficult and we only succeeded in flushing them a second time. Fortunately, we did get on a pair briefly later in the day for a few photos.
Starting back west across the top of the San Diego Trough we came on a Minke Whale that gave us a brief look before disappearing. Minkes are the smallest baleen whale and rather common, though not always seen. Their small blow and stealth attitude make them hard to find, which is helpful as they are the only baleen whale still hunted legally by some counties. Other marine mammals seen throughout the day included both Common and Bottle-nosed Dolphins.
The return to the Nine Mile Bank found several areas of breaking fish and a frenzy of bird activity, consisting mostly of Black-vented Shearwaters, Elegant Terns, and a mix of some others, such as several Brown Boobies. We also had two or three jaegers, including a near adult Long-tailed Jaeger seen right over the top of the boat. This is another species that passes well to our west most and is sometimes missed during migration. This bird caused confusion initially because it showed some dusky feathers in the neck, unlike the clean white throat and neck of an adult. We watched it make a couple of feeble attempts to harass Elegant Terns. They were just a little too big for the Long-tailed Jaeger.
One other jaeger here gave us a little confusion and excitement when the shout went out South Polar Skua! It was actually a very dark Pomarine Jaeger, not skua-like except for the dark coloration and large white wing flashes. Paul corrected our mistake quickly and we moved on to start our return to Mission Bay.
It was a nice mix of birds, a few rarities, and a manageable ocean today. We felt pretty good about the trip overall.
Dave Povey
Species list for Mission Bay:
Marbled Godwit
Willet
Spotted Sandpiper
Western Sandpiper
Heermann’s Gull
Western Gull
Caspian Tern
Royal Tern
Elegant Tern
Brandt’s Cormorant
Double-crested Cormorant
Brown Pelican
Great Blue Heron
Great Egret
Snowy Egret
Black-crowned Night-Heron
Barn Swallow
Offshore Birds:
Mourning Dove
Marbled Godwit
Red-necked Phalarope
Red Phalarope
Pomarine Jaeger
Long-tailed Jaeger
Craveri’s Murrelet
Sabine’s Gull
Heermann’s Gull
Western Gull
Caspian Tern
Common Tern
Arctic Tern
Royal Tern
Elegant Tern
Leach’s Storm-Petrel
Ashy Storm-Petrel
Black Storm-Petrel
Least Storm-Petrel
Sooty Shearwater
Pink-footed Shearwater
Black-vented Shearwater
Brown Booby
Brandt’s Cormorant
Pelagic Cormorant
Marine mammals:
Minke Whale
Bottle-nosed Dolphin
Common Dolphin
California Sea Lion
Fishes:
Mako Shark
Mola mola ( Ocean Sunfish)
California Flying Fish
Pacific Bonito
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