Proposal (941) to South American Classification Committee

Add Pterodroma [macroptera] gouldi to the South American list

BACKGROUND.

SACC has passed but not yet implemented a proposal to divide Procellaria gouldi from macroptera. The North American committee has already made this change. Here is the current proposal for those who require a refresher on the issue, which seems relatively clear-cut as far as seabirds go:

https://www.museum.lsu.edu/~Remsen/SACCprop929.htm

We currently have macroptera in the broad sense on the checklist based on a specimen from Brazil. The photos of the specimen show dark around the bill and throat, and the Atlantic distribution all line up with macroptera in the narrow sense. Here is a pdf of the publication used to accept the species to the South American list.

https://laatm.furg.br/images/pdf/articles/014-BugoniBullBrOrnitholCl12652-54Pmacroptera.pdf

NEW INFORMATION

On Page 25 of the following issue of La Chiricoca (Chile) a well photographed Grey-faced Petrel Pterodroma gouldi is documented. There have been reports of the species previously, but no documentation.

http://www.lachiricoca.cl/wp-content/uploads/2018/03/La-Chiricoca-21_part5_c.pdf

The image shows the broad winged, barrel-chested look for this species pair, along with the white on throat and around bill. Also, it has all dark primaries, no pale bases as in solandri. The big bill and shape exclude the more petite ultima, or Kermadec etc.

Furthermore this month, a new photographed record of gouldi has occurred, much farther north in the country. Perhaps with more exploration through pelagic trips we will find that this is a rare but regular visitor to Chilean waters? This record has not been published yet, but again the thickset look, large bill can be seen as well as the white around the bill base, extending to the throat:

https://ebird.org/checklist/S109409539

RECOMMENDATION

I recommend we add gouldi to the South American list based on these Chilean records, and retain the Brazilian record as macroptera.

Alvaro Jaramillo, May 2022

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Comments from Lane: “YES. Given the soon-to-be implemented split of P. macroptera and P. gouldi, and the presence of records of both taxa from South American waters (based on what Alvaro reports above), we need to include both on the SACC list.”

Comments from Steve Howell (voting from Remsen):

“NO.

“Years ago, California's first "Dark-rumped Petrel" was mistakenly thought to be a Gould's Petrel P. leucoptera, and Chile's first (?) P. leucoptera was misidentified as a Galapagos Petrel; California's first Great-winged = Gray-faced Petrel was misidentified at the time as Murphy's, and I won't even get into the recent Bulweria debacle in California. The CBRC has accepted (!) "good photos" of Stejneger's Petrel as Dark-rumped Petrel, and a few years ago I saw published photos in NAB of "Oregon's first Dark-rumped Petrel" which was also a Stejneger's!! The classic Solander's/Murphy's Petrel problem is exemplified by a series of good photos from British Columbia (Oct 2009) widely regarded as showing a classic Solander's but which show a Murphy's, and I think people have finally all come around to Murphy's on that bird, but perhaps not. Just some context for my comments on the Chilean reports of putative Gray-faced Petrels and a few examples of the challenges of interpreting photos.

“I have experience with many hundreds of both Great-winged taxa, and most recently (March 2020) got to see lots of Gray-faced and, on one pelagic off SE Australia, observed Gray-faced and Great-winged together several times, very educational. Until then I hadn't fully appreciated the structural and jizz differences, but even so, one or two distant birds were left unidentified, and one close bird was reidentified from photos. As noted and shown by Howell & Zufelt (2019), the pale face is variable on both taxa and not necessarily a diagnostic feature.

“July 2015 photo in Chiricoca (p. 25 of Aug 2016 issue). This image is not good enough resolution for me to feel confident about the ID, but if I had to guess I would tend towards macroptera and not gouldi based on overall structure; the head looks relatively 'small' with a dark eye patch, classic for macroptera but not so good for gouldi (which has more of a big bulbous head, thick neck); the extent of pale in the face is ambiguous; and the photo is not sharp enough to accurately evaluate bill size and shape, which look plausible for either taxon; together with head size and pattern, I could see the bill fitting well with macroptera, but somebody thinking the bird is gouldi could probably imagine the bill as bigger and stouter like that taxon!

“May 2022 eBird record. Fernando Diaz from Chile sent me these photos last month for comment and my first impression was "nice, Murphy's Petrel." Then I read on to find it was thought to be Gray-faced... Simply from photos I can see this really isn't an easy call; so, I looked harder and compared numerous photos and I still can't convince myself it isn't a Murphy's (male, presumably, with relatively big bill). Besides simply a jizz thing and my initial reaction, note the apparent gray tones to fresh upperparts and upperwing coverts (sooty brown on gouldi), relatively long and 'slim, squared' nostril tubes (shorter and 'lumpier' or rounded on Gray-faced); the relatively brown and faded greater coverts age it as older than first cycle, but other than that nothing much I can say.

“Consequently, based on these photos I would not accept gouldi for Chile or South America: the first bird could be gouldi, but it gives me more the feel of macroptera, and the second looks more like a Murphy's Petrel, which occurs regularly off Chile, albeit usually farther offshore. Leaving all birds as unidentified Pterodroma sp. would be the most responsible course of action (much as birders hate doing that!), but to my mind the case for gouldi in South America remains unproven. Attached FWIW a quick screenshot comparison of the May 2022 bird off northern Chile (center) with GF, GW, and MUPEs from my files.

Comments from Claramunt: “YES. My impression is that the birds in the Chilean photos are indeed P. gouldi. The combination of whitish face, dark underwings, and strong bill seem diagnostic. The lighter face in some individuals of macroptera is more restricted and diffuse, not contrasting and with a “scaly” effect as in P. gouldi. P. ultima would show lighter primaries. But I admit, the photos are not ideal. The photos of the second birds are dark, but with a bit of light adjustment, the bird shows the typical pattern of P. gouldi, very similar to the P. gouldi in Steve’s photo from Australia. Looking forward to hearing other opinions.”

Additional comments from Steve Howell: “I still can't rule out Murphy's, and all the apparent silvery gray plumage is odd for GWPE or GFPE, although perhaps a function of lighting. Bill doesn't look stout enough for gouldi; most people forget that all Pterodroma (except Cookilaria) have relatively stout bills.”

Comments from Brian Sullivan (voting for Bonaccorso): “NO”

“As Steve Howell rightly points out, determining the identification of mystery seabirds based on a single photo, or even a series of photos, can be fraught with problems. It’s extremely difficult to get a sense of the bird as one would in the field based on images, and you’re left looking at minutia that may or may not be helpful for ID. The best approach is to wait to accept P. gouldi to the South American list until a well-documented and irrefutable set of images exists. I suspect now that birders are aware of the possibility, more attention will be paid to these birds and better documentation will be had soon enough.

“Regarding the individual shown on Page 25 of La Chiricoca (21), the image clearly looks good for one of the species pair P. macroptera/P. gouldi, but the resolution is insufficient to tell what species is involved.

“Having admittedly little real-world experience with these taxa (but a lot with seabirds more generally), I spent a fair amount of time looking through material in eBird/Macaulay Library to compare the recent report from Chile on 7 May 2022 (https://macaulaylibrary.org/asset/446023131) with examples of these taxa from elsewhere. I have included two montages showing the Chile individual (lower left in both montages) compared with various individuals of P. gouldi (top) and P. ultima (bottom). My gut impression favors P. gouldi based on this crude comparison, but I can’t be sure based on the single image of the Chile bird that has been provided. The bill looks on the larger and thicker side to me with a pale area at the base of the maxillary unguis, which seems present on all the P. gouldi individuals but less so, or at least less apparent, on the P. ultima examples. I have no idea whether this is a field mark that has been evaluated previously for distinguishing these two taxa. That said, I just can’t be sure what this bird is. If there are more photos of this individual, even blurry ones, it could help clarify the ID.”

“For now, the most conservative approach is to wait for a better example before adding P. gouldi to the list.”

vs. P. gouldi:

Vs. P. ultima:

Comments from Stephen F. Bailey (voting for Robbins): “NO, although I do think it is highly probable that the May 2022 bird is a Gray-faced Petrel (gouldi). But is there ANY truly definitive field character that can separate gouldi and macroptera in one photograph?! I’m getting ahead of myself.

“First, the photo of the July 2015 Chiricoca bird is suggestive but not good enough for a definitive identification. I have not felt it worthwhile to attempt any species-level identification, based either on my knowledge or on the opinions already expressed in these deliberations.

“Gray tones versus brown tones in photos of tubenoses is HUGELY dependent on ambient lighting, especially the degree of cloud cover, as is amply demonstrated by Brian Sullivan’s montages of both Gray-faced and Murphy’s petrels. To me, the one photo of the May 2022 bird shows both gray and brown in its plumage and the overall appearance of grayish tones is not very informative. I attribute that grayness mostly to a heavy cloud cover. (Note the lack of any blue-sky tone in the photo’s background.) In direct sunlight, that bird would have looked much browner.

“The May 2022 photo is excellent, and it shows what I think is a definitive bill character that eliminates Murphy’s Petrel. This “new” bill character is one of detailed STRUCTURE not apparent size or overall shape. In all photos of both gouldi and macroptera the “saddle” of the bill between the nostril tubes and the maxillary unguis is distinctly more concave, with the proximal portion of the maxillary unguis rising up into a higher convex curve. All photos of Murphy’s Petrel, by contrast, show a distinctly flatter, less-concave transition from the bill saddle into the more-convex maxillary unguis. This gives the bills of both gouldi and macroptera a more-constricted-middle and more-bulbous-tipped appearance versus the straighter, less-constricted appearance Murphy’s Petrel. BUT it is NOT this general appearance that I refer too, but rather the specific concave dip of the bill “saddle” between the nostril tubes and the maxillary unguis. Note that some larger-billed Murphy’s Petrels (e.g. Howell’s Oeno Island photo and especially Sullivan’s upper left photo in his montage of Murphy’s) show almost the same degree of “bulbous tip” after a “constricted” bill-middle as some gouldi and macroptera. But the Murphy’s all lack the more-concave “saddle” before the distinct rise into the higher maxillary unguis; instead they show a straighter, flatter transition to the maxillary unguis. The May 2022 photo clearly shows the bill structure of gouldi and macroptera, not that of Murphy’s Petrel. This is why I consider Murphy’s Petrel to be eliminated for the May 2022 bird.

“That leaves the question of whether the May 2022 bird can be identified as Gray-faced Petrel versus Great-winged Petrel. Although its rather extensive pale face is quite suggestive, apparently it is not diagnostic (fide Howell. and Howell & Zufelt 2019). As for Howell’s judging this bird as showing “relatively long and 'slim, squared' nostril tubes (shorter and 'lumpier' or rounded on Gray-faced)”, I have two observations. First, Howell was contrasting ultima versus gouldi, but this character could still be relevant for macroptera versus gouldi; Howell’s comparative photo of gouldi shows a shorter, “lumpier”, less-squared nostril tube than shown by his comparative photo of macroptera. However, the 8 photos of gouldi assembled by Sullivan show variation encompassing both shapes of nostril tubes, and more than half of them show the longer, more-squared nostrils. Assuming that these 8 photos are all (or even most) correctly identified as gouldi, we can conclude that the shapes of gould nostril tubes are not consistently different from macroptera, at least in this character. The 8 reference photos of gouldi all show an extensive pale face, and I suspect that the location of most or all of the 8 photos was a factor considered in their identification. Therefore, I have no reason to question their identification, at least in the aggregate. The May 2022 bird’s nostril tubes therefore seem to fit within the variation for both gouldi and macroptera.

“I cannot evaluate Howell’s “structural and jizz differences”, as I lack his comparative field experience, and we have only one photo, albeit an excellent one.

“So where does all this leave me in the identification of the May 2022 bird? At this point I find that I have to vote “no” because I don’t know of ANY truly definitive field character (or combination of field characters) that can separate gouldi and macroptera in one photograph. If that is true, and until further knowledge changes that, then there will NEVER be a bird around South America identifiable to gouldi with only photographic evidence! That conclusion is not going to sit well with many people.

“Nevertheless, I do think that the May 2022 bird is most probably a Gray-faced Petrel, i.e. gouldi. All the characters that I can see and trust from the single photograph are consistent with that identification. As discussed above, I am confident that ultima can be eliminated based on my “new” bill character. All the bill characters as I see them are consistent with either gouldi or macroptera. The extensive pale face is strongly suggestive of gouldi over macroptera, but apparently not definitive. The biogeography of gouldi being more expected on the Pacific side of South America (and macroptera more expected on the Atlantic side of South America) is logical but at best suggestive; range should be the LAST bit of evidence considered in the case of such wide-ranging seabirds.

“If one were to vote based on “the preponderance of the evidence” and the “high probability” of the identification being correct, then I think one can vote “yes”.  But if asked whether I consider a definitive identification to have been confirmed, I have to vote ‘no”.”

Comments from Pacheco: “NO. A kind of "Precautionary Principle". Given the degree of uncertainty about the identity of the photo of Pterodroma published in "La Chiricoca" by consensus admitted by three invited experts. I agree with Brian Sullivan: “The best approach is to wait to accept P. gouldi to the South American list until a well-documented and irrefutable set of images exists.”

Comments from Stiles: “NO. While I would gladly cede my voting slot on this one, given the answers of three experts already consulted, this might not be feasible - as it stands, I can only vote NO on the same basis as stated by Fernando (if the experts cannot agree that the evidence is sufficiently conclusive best to wait for better evidence to clinch the case, e. g., a good series of photos or a specimen.”