5 OCTOBER 1997. MEXICO:
SEABIRDS, MARINE MAMMALS, HURRICANES Just finished a six-week research cruise onboard the NOAA R/V "David Starr Jordan" operating in the very shallow waters (mostly less than 100 meters) of the upper Gulf of California (Sea of Cortez) and Colorado River delta and mouth (mid-Aug to late-Sep). Having never worked in this part of the Gulf before, I have no comparative experience as to how the region may have been influenced by the current ENSO event and analyses of oceanographic data are incomplete. I suspect nothing much really. If anything, it was much more windy than was expected and as suggested by the local fishermen. We were expecting mostly calm Beaufort 0-2 sea states. Up until about mid-September, the almost relentless winds were humid tropical southeasterlies, 15-25knots, with resulting sea states at B-4 to B-6. This hampered study efforts but had a cooling effect on the air temperature keeping it down to a relatively tolerable low-mid 90's F (31 - 33C) while sea surface temperatures hovered around 90 F (31 C). On land (adjacent desert areas, NE Baja & NW Sonora, Mexico) daily daytime temperatures maintained reasonably normal desert levels 105 - 115F (40 - 46C) but with heat "comfort" indices reaching extremes as high as a blood boiling 160 F (71 C) -- this figure via local TV received aboard ship from Yuma, Arizona. Typical overnight low temperatures were often in the humid low to mid-80's (26 - 30C) which were warmer than normal. Our cumulative incidental seabird sightings seemed to indicate nothing really out of the ordinary relative to El Niño. The upper Gulf of California seems like an odd place to find the SOUTH POLAR SKUA (typically 3-8 per day -- possibly same birds I suppose), but this species is apparently a regular part of the summer avifauna here with concentrations as high as 35 birds counted in a single sweep during a 1993 visit to this area, then associated with fishing activity (pers.com. Bob Pitman & Mike Force). [WHY has this species not yet turned up at California's Salton Sea??? ...or has it? "Nora"?? If the South Polar Skua can cross the vast icy desert of Antarctica to reach the South Pole at Admundson-Scott Base (the only species of bird ever recorded there), then a little bit of scalding hot sandy desert shouldn't be such an impossible barrier].
A few to several dozen Sooty and Pink-footed Shearwaters were present daily throughout the period with Sooties all the way up into the delta and along Sonoran desert beaches. The Sooty Shearwaters certainly appeared to be way out of their element in these "hot" waters, appearing severely bedraggled in ragged states of molt, sickly, and oily "slick" as the plumage appeared wet and soaked and not shedding sea water properly. The Pink-footed's appeared to be in much better shape than the Sooties and seemed much more at home in somewhat deeper offshore waters (>40 m) as were the majority of Black-vented Shearwaters.
Otherwise, the characteristic residents of the region [Black-vented Shearwater, Black and Least Storm Petrel, Red-billed Tropicbird, Brown and Blue-footed Booby, Brown Pelican, Magnificent Frigatebird, Heermann's and Yellow-footed Gull, and Elegant, and Common Terns] were plentiful, seen daily, and appeared to be doing well. There were no Craveri's Murrelet sightings and none were expected. The only Laughing Gull was an immature on 9/23. A panga trip in the channels around Pelican and Montague Islands inside the mouth of the Rio Colorado on 9/21 noted 200-300 Black Skimmers, a few Gull-billed Terns, American Oystercatcher, Wilson's Plovers, and numerous large waders, especially Long-billed Curlews and Marbled Godwits, et.al., and sneaky "small-sized" Bottle-nosed Dolphins (_Tursiops sp._) that could easily be mistaken for Vaquita (a very rare and endangered porpoise Phocoena sinus) by their slow snap rolling "porpoise-like" behavior in those incredibly turbid waters, but definitely no Vaquita there.
Rarities to the upper Gulf, though probably not to be unexpected included Buller's Shearwater (1), Masked Booby (3) [both yellow and orange-billed forms], Red-footed Booby (1), dark-rumped Leach's (2-3), and Galapagos Storm Petrel (1). A single Wilson's Storm Petrel pattering, planing, and skipping along the surface amongst several thousand Black and Least Storm Petrels in the wake of a fishing boat north of the Midriff Islands, and Audubon's Shearwater off Guaymas were most notable, and both seen during a refueling transit run on 9/01.
Numerous and immense spectacular flocks of migrating Black Terns (tens of thousands!!) and Least Terns (many hundreds to low thousands) were present in waters off Guaymas on 9/01. During the return transit from Guaymas to San Felipe, the "Mother of tern flocks" a massive dense feeding frenzy of 25-50,000 Black Terns were seen off Isla San Sebastian at sunset on 9/04 stretching for more than a mile and looked like a black cloud of insects in the distance!! Sabine's Gull, and all three jaeger species [Parasitic, Pomarine, and Long-tailed (rare)] were regular in small numbers in the upper Gulf through the period. Most of these birds were immature and may have arrived from overland.
There were three Pacific Hurricanes affecting Baja during the study. 40-50 knot pressure gradient SSE winds between "Ignacio" off western Baja and High Pressure over Texas pushed several hundred Sooty Shearwaters and 2-3 dark-rumped Leach's Storm Petrels into Colorado River delta area on 8/16. Superstorm (Category 5) "Linda" turned west off Cabo San Lucas, a relief to everyone and had no effect on the upper Gulf.
"Nora" (Category 1) cut across central Baja from the Pacific side and scored a direct hit on San Felipe and delta area on 9/24-25 (2300 - 0800hrs). At the storms height, driving east winds were sustained at 60-80 knots for about three hours (0500 - 0800hrs) and 13.2 inches (~335 mm) of rain fell. At 0800 hrs, the whole thing abruptly stopped dead, the sun came out and the storm was over. We thought it was the eye, but in fact the storm was indeed over not realizing that this storm had a clockwise rotation. Substantial damage was done to the boat harbor and protective breakwater with about 30 pangas busted up and sunk (including our's), some structural damage and flooding in town, and wide-spread desert flash flooding caused extensive road damage. Mike Force and I had just disembarked in San Felipe as "Nora" approached and we ended up stranded there for four days until rescue arrived to take us and scientific gear to San Diego.None-the-less, it was an "interesting" adventure watching the ongoing fury at beach-side from the Las Misiones Resort Hotel where we had a commanding view of the whole show while hoping that it wouldn't get worse and trying to stay out of the line of fire from flying debris, glass, and breaking windows.
There were no seabirds of note in the immediate wake of the storm at San Felipe other than the offshore regulars having been blown near shore. However, storm fallout reported by birders in desert birding locales of SE California and Arizona included a scattering of many of the characteristic species of the upper Gulf. At least some of these included, Black and Least Storm Petrels, Black-vented Shearwater, Red-billed Tropicbird, Brown and Blue-footed Boobies, and Magnificent Frigatebird.
A sub-adult "yellow-billed" Masked Booby observed on 9/23, just ahead of "Nora" by Mike Force and me in the Upper Gulf east of "Rocas Consag" may be particularly notable and may have either been a belated lost gift of "Linda", or was pushed well ahead of "Nora" which had stalled south of Cabo for a few days, or perhaps was assisted by both.--Richard RowlettPagodroma@aol.com
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