Saturday, October 29, 2016

My Story of Newton

My Story of Newton

Wednesday 09/07/2016 14:58MST: With the center of post-tropical cyclone Newton passing over, I am standing near a small wastewater treatment facility attempting to study and photograph several storm-petrels. I had checked this small body of water earlier in the day for any storm driven birds as well as several nearby small golf course ponds. I had found none. At 14:20 MST Richard Wilt reported to the Tucson Rare Bird Alert a white-rumped storm-petrel at the Amado Water Treatment Plant. Andrew Core immediately posted the report to both the AZ/NM list server and the Arizona Birding Facebook Group.

I arrived back at the Amado WTP at 14:58 MST. The final advisory from the National Hurricane Center for this storm was issued at 15:00 MDT (or 14:00 MST). This advisory stated that the center of the storm was located near latitude 31.6 north,
longitude 111.2 west, 12 miles southwest of the Amado WTP. The storm was reportedly moving NNE at 18 mph and expected to turn northeast. This means that the center of the storm was moving over this location. Weather conditions while I was there varied from no rain to light rain to short periods of heavy rain; winds were mostly gusty from the southwest & south 10-30 mph with some period of calm, heavy overcast. Heavier rains & winds generally coincided. Post-tropical cyclone Newton was passing over the area as a tropical depression/remnant low.

Nearly immediately upon my return, I see a storm-petrel with a white rump patch and then another and then there was an all dark storm-petrel and a phalarope that I misidentified. I began studying and photographing the storm-petrels. At this moment I felt very lost; several years has past since I was out on the ocean looking at storm-petrels. What was I looking at?

While studying and photographing the storm-petrels I kept reminding my self that I needed to scan the skies for other birds. On one such scan, at 15:09 MST, I detected a larger bird coming in from the south. Initially I thought this bird was a booby, it was about 500 yards away, varying between estimated 50 to 100 feet above ground, and quickly heading roughly towards me. I made a conscience decision to not use the binoculars; the speed at which things were happening meant that I could lose any photographic opportunities if I was fumbling between binoculars & camera. As it approached and I got a more of a side view I realized this was a shearwater. The shearwater circled over the south half of the pond once or twice, the moved north over the east side of the pond before swinging west over the north end of the pond and past my position. The bird continued west over Interstate-19 and Arivaca Junction when it was lost visually. It was difficult to get focus on the shearwater initially but once I did, I followed it with the camera. In 42 seconds I took 64 images of the shearwater, mostly in bursts. Once the shearwater was out of view and after a few seconds of scanning for its return or anything else I took a breath, sent a post off to the AZ/NM list server and returned to studying & photographing the storm-petrels for the next two hours.

Soon after the shearwater disappeared, other birders began arriving on the scene. At first it was those from Green Valley, eventually those from Tucson, and later from Phoenix. Our discussion mainly focused on the storm-petrels with white rumps. There were at least four of them now plus the one with the dark rump. All those with white rumps appeared to be the same species. They were the same size, shape & structure, flew similarly, same pattern of white on the rump, same shade of black-brown, and had the same faint but visible ulnar bar on the upper wings. It seemed that all of us were trying to turn these birds into “Leach’s” Storm-Petrel the most likely white-rumped storm-petrel found off the west coast and the only one previously recorded in Arizona. Which one? The species formerly known as “Leach’s” had been split into three species Leach’s, Townsend’s, and Ainley’s. I knew none of the details of the split or how to tell the sibling species apart or what their ranges were. I’m pretty sure no one in the crowd knew either. Having taken hundreds of photographs I begin thinking about retreating to home where I can study my images and get more information about and possibly identify the white rumps storm-petrels. About this time I learn that Chris McCreedy is seeing storm-petrels at Patagonia Lake some 15 miles to the southeast. Apparently from the photos he shared, Wedge-rumped Storm-Petrel was being considered. I began to head home but got a message that a friend had just arrived and wanted my assistance. I’m not but two hundred yards away from the pond so I turn around. As I am looking for another spot to park, I see a small appearing all dark storm-petrel flying west over the frontage road and away from the pond. That triggered a question – “Did I take any photographs of the dark storm-petrel on the pond?”. I find a parking spot and my friend (they are all my friends, just some more so than others) and set out to relocate the all dark storm-petrel if it hadn’t just left. It was still there and while getting my photographs of this bird I determined it was a Least Storm-Petrel by the short rounded tail. I must have peaked at a field guide sometime while in my truck. Least Storm-Petrels have only been recorded in the state a few times and always in conjunction with a tropical storm. I also noticed that the storm-petrels with white rumps were nearly the same size as the Least. This was to become an important feature aiding us in determining what species we were dealing with. Several of us watched one of the white-rumped birds flying away from the pond only to find four with white rumps still on the pond along with the Least. More friends showing up and finally at about 17:30 I decide I need to leave. I follow some friends up the frontage road and just before we reached the south Green Valley development, an all black looking storm-petrel flew east to west over the frontage road and then curves back to the east. I stop, jump out of my truck with my camera but am unable to find the bird. It appeared larger than the Least we had just been looking at however without any context for size and no photographs this one was going to be reported up as “storm-petrel sp.”. We check one nearby golf course pond and then I head home.

Upon returning home, I downloaded photos from the camera to the computer. I had in excess of 600 photographs to sort through. My first priority was to determine what species of shearwater I had seen. Many others had seen the storm-petrels and besides I think we had one of them figured them out. I and only one other person saw the shearwater. I do not know who this other person was. He either left after the shearwater or got mixed in with the crowd that arrived later. I was focused on the birds.

Now began the process of elimination and inclusion. No notes were taken in the field though a quick look at several of the photographs confirmed what I did recall; a long thin bill, slim body, wide base of wings appeared greater than body width, longish tapered tail, dark above, and pale below including much of the underwing. I selected several of the better photographs, cropped them to show a nearly full from image of the bird and began the comparison with drawings in the only seabird guide I had at the time, Seabirds An Identification Guide by Peter Harrison 1983. The fairly long and thin bill eliminated Gadfly petrels in my opinion and in short order I settled on Pink-footed Shearwater. Moments later I forwarded one photographs of the shearwater and my tentative conclusion to David Vander Pluym. Nearly immediately I received the reply “Wedge-tailed”! I flipped the page of my seabird guide and yes; Wedge-tailed Shearwater is a better match.

Wedge-tailed Shearwater 

Between the time I began looking at photographs of this bird and when I consulted with others, I had determined that I was dealing with one of the larger shearwaters in the former genus Puffinus. [Now these larger shearwaters are in the genus Ardenna.] I eliminated the gadfly petrels (Pterodroma) based on the relatively long thin bill of this bird. The thickness relative to the length of gadfly petrel bills gives them a heavier bulkier and somewhat stubby bill appearance. Black-vented and Manx Shearwaters, though patterned similar to the bird I photographed, were discarded for consideration based on apparent size. The few times I have seen either of these two species they appeared small. Narrowing down the candidates further, Buller’s Shearwater has a bold upper wing pattern that this bird lacked. I thought I was left with just three large pale bellied shearwaters for sort through – Cory’s, Greater, & Pink-footed. Cory’s – no, range and white vent/undertail coverts. Greater – no, range and white collar nearly isolating cap. Pink-footed – yes, common on the west coast, an okay match on overall pattern, pink feet. At the time I ignored the fact that Pink-footed Shearwaters have pale bills with a very contrasting dark tip whereas the bird I had seen had a gray bill with perhaps a slightly darker tip. With my misidentification in hand, I sent a photograph showing the underwing & body of this bird to David Vander Pluym. David and Lauren Harter immediately replied that I had seen and photographed a Wedge-tailed Shearwater. I turned the page in my seabirds guide and there it was. All the characteristics visible in my photographs were depicted and described by Harrison. This report of Wedge-tailed Shearwater, if accepted by the Arizona Bird Committee, will be the first record of the species for Arizona and only the second inland record for the US.
Wedge-rumped Storm-Petrel

Before I left the Amado WTP, I believed we had identified one of the storm-petrel species and had been given some good hints for the other. The all-dark bird was identified as a Least Storm-Petrel. It was small appearing, not much larger than the swallows smarming over the pond, with a rounded or wedge-shaped tail. Other similar appearing species are roughly 30%-50% larger than Least (therefore would have dwarfed the swallows) with forked or notched tails. The white-rumped birds were approximately the same size as the Least Storm-Petrel when viewed sitting on water side-by-side and in flight, maybe slightly larger. This size comparison was useful. Contenders for the white-rumped birds included Leach’s, Townsend’s, Ainley’s, Wedge-tailed, and Wilson’s Storm-Petrels. All but the Wedge-tailed should appear visibly larger than the Least Storm-Petrel. The most obvious feature on the white-rumped storm-petrels provides us with the clincher (in my opinion). The white patch at the base of the tail is the upper tail coverts. On Leach’s, Townsend’s, and Ainley’s the white rump patch is rounded or even lobed and the maximum extent seems to be less than 50% of the length of the tail. On a Wilson’s the shape of the white patch is likened to a band across the basal third or so of the tail. On all four of the white-rumped storm-petrels observed, the shape of the white patch was, dare I say, wedge-shaped. The maximum extent at the point of the wedge was about 70% the length of the tail. Additionally, the white patch wrapped around the edges of the base of the tail. Therefore, at least some of the outer undertail coverts are white. I believe this latter feature occurs on only one of the species I was considering. So the white-rumped birds were identified as Wedge-rumped Storm-Petrel. While I am sure there are other features on both of these species that could be used to nail down these identifications (wing shape & size, tail shape & length, manner of flight in varying winds, perhaps even head shape) I do not have the experience necessary to decipher them.

Least Storm Petrel 

The following few days also held a few moments of excitement though nothing near the intensity of those hours during the storm’s passage. I joined Mark and Molly on Thursday for the day after the storm search. Without finding anything usual at Amado WTP we proceeded to Patagonia Lake. There we met up with David & Lauren, saw a couple of Common Terns but no storm-petrels. David & Lauren mentioned that they had picked up a Wedge-rumped Storm-Petrel the previous night at the rest area along I-19 south of Green Valley and taken it to a Tucson rehabber. We received a report of a storm-petrel at Bensen STP, so off we went. By the time we got to Bensen, the storm-petrel was long absent. A Black-bellied Plover observed at a nearby golf course may have been a migrant forced down by the storm the previous night. A report of a probable Wedge-tailed Storm-Petrel in Mesa prompted David & Lauren and others to head homeward via Riverview Park. Mark, Molly, & I decide to call it a day. On Saturday, yes three days after the storm, an all dark storm-petrel was discovered at Bensen WTP. Louise and I arrive mid-day and find a group of birders looking at what we determine to be a Black Storm-Petrel. This bird was observed and photographed by many. I believe this was the only Black reported as a result of Newton. The only prior record of Black Storm-Petrels in Arizona was at Lake Havasu after Nora (1997).
Black Storm-Petrel 

Discussion of species ranges

Wedge-tailed Shearwater [Ardenna pacifica] ranges throughout the tropical & subtropical Pacific and Indian Oceans. In the eastern Pacific Ocean they are known to breed on San Benedicto Island about 350 miles west of mainland Mexican and 250 miles south of the south tip of Baja California Sur. According to Howell, 90% of these birds are dark-morph. Apparently light-morph birds are locally & seasonally common off the west coast of Mexico north to about 20 degrees north latitude from November to June. From July through October there appears to be smaller numbers of light-morph bird however they range further north and can be found around the tip of the Baja Peninsula and into or at least at the mouth of the Gulf of California. It is presumed that a majority of these light-morph birds are non-breeders wandering from the Hawaiian Islands [Howell, 2012]. While Wedge-tailed Shearwaters are regular off the west coast of Mexico north to the south end of the Gulf of California and around the south end of the Baja Peninsula. They are casual off the west coast of the US and there is a single inland record at the Salton Sea. There are about 13 records, mostly from California plus two from Oregon and one from Washington. These records include both light and dark morphs however light morphs appear more numerous in the fall. I was not able to find any records or reports of this species from the west coast of Baja or in the Gulf of California north of La Paz.

Wedge-rumped Storm-Petrels [Oceanodroma tethys] range along the west coasts of South & Central America northward along the west coast of Mexico and the southern half of the west coast of Baja and into the southern portion of the Gulf of California. There are two subspecies recognized that may represent two species, O. t. tethys (Galapagos Storm-Petrel) and O. t. kelsalli (Peruvian Storm-Petrel). Even though there is much overlap in overall ranges each has a distinct breeding region as indicated by their nicknames. During their non-breeding season O. t. kelsalli occurs along the west coast of the Americas from Chile to Baja and tend to occur in continental shelf waters more frequently than O. t. tethys.

Least Storm Petrels [Oceanodroma microsoma] is commonly found around Baja California, in the Gulf of California, and south along the inshore waters of Mexico & Central America. It also regularly occurs north along the coast to central California. It breeds off the west coast of Baja and a few islands in the gulf. Least Storm-Petrels have been pushed into the desert southwest several times by tropical storms, including Arizona.

Black Storm-Petrels [Oceanodroma melania] is a local breeder on islands off the coast of southern California and northwest Mexico, including the Gulf of California. They are known to occur over inshore waters from the southern California southern to Central America. Black Storm-Petrels have been pushed into the desert southwest several times by tropical storms, including Arizona.

The Storm and Speculation

Tropical Depression 15-E formed approximately 220 miles south-southwest of Manzanillo, Colima, Mexico on Sunday 9/4/2016. At that time it was moving north-northwest at 2 mph. The potential for this storm to develop was recognized a week prior and was tracked as a system of disturbed weather as it moved along the coast of Guatemala and southwest Mexico. This storm was expected to impact the southern portion of Baja California, approximately 560 miles NNW late Monday night or Tuesday. Six hours after the initial advisory, this storm was upgraded and named. It now had maximum sustained winds of 40 mph and had accelerated forward movement to 8 mph still NNW direction. Newton continued strengthen and accelerating and by mid-day Monday 9/5/2016 was declared a hurricane. At this point it was 215 miles SE of Cabo San Lucas moving NW at 16 mph with maximum sustained winds of 75 mph. Hurricane Newton made its first land fall early Tuesday morning 9/6/2016 near Cabo San Lucas with 90 mph sustained winds and movement NNW at 18mph. Newton reemerged over open water late Tuesday near Santa Rosalia Mexico moving north at 17 mph with an excepted turn to the NNE on Wednesday. By 3am MDT Newton had made its second landfall and been down graded to a tropical storm. Over the next 12 hours, Newton weakened yet continued movement to north to north-northeast at about 18 mph into southern Arizona. The 12:00pm MDT advisory still had Newton as a tropical storm with winds of 45 mph centered 25 miles SW of Nogales, AZ. Three hours later the final advisory of Newton was issued, 25 miles WNW of Nogales and maximum sustained winds of 35 mph.

The satellite image with the storm track is from a Wikipedia article discussing Hurricane Newton, the hand drawn shaded areas shows wind speeds (yellow = tropical storm, red = hurricane) data from NHC, and the arrowed arcs show how I believe the winds swept birds along the west coast of Mexico and into the Gulf of California.

I speculate that the cyclonic winds around the storm center pushed seabirds northwest along the west coast of Mexico and perhaps out to sea. As the storm approached the Baja Peninsula, the “out to sea” route was effectively cutoff and seabirds were funneled northwest into the Gulf of California. The three species of storm-petrels found in Arizona as a result of this storm inhabit the continental shelf waters where Newton’s winds could have swept them along the west Mexico coast and into the Gulf of California. Even while Hurricane Newton was over land in Baja, tropical storm force winds were occurring all the way across the Gulf of California and along the west coast of Sinaloa and Sonora. As the storm continued to move NNW along the peninsula, seabirds would continue to be pushed northwestward in the Gulf by the large swath of tropical storm force winds. Once the storm emerged over the waters of the Gulf, the northwest path was cutoff and the seabirds either were pushed over land or got “trapped “ in the center of the storm. By this time the storm’s eyewall had dissipated and the calm at the center of the storm was history. As the storm moved northward towards Arizona, it continued to disintegrate. It seems most likely that the seabirds rode the relative calm of the center of the storm north 200+ miles until they found bodies of water on which to rest and potentially feed. During the passage of the storm, all the seabirds were reported from areas along or east of the reported track of the storm’s center. The initial timing of these observations roughly coincides with the passing of the center of the storm. Geography, locations (and timing) of observers, and locations of bodies of water are additional factors that need to be looked into.

As an almost final note: Specimens of two of the Wedge-rumped Storm-Petrels were measured and determined to O. t. kelsalli (Peruvian Storm-Petrel).

Now a final note: Where are my photographs? 

No comments:

Post a Comment