Gisborne pelagic (Oct 21) addendum: Manx Shearwater

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Matthias
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Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby Matthias » Sun Oct 29, 2017 10:53 pm

Hi,

on the pelagic trip off Gisborne last Saturday (21st) with Russ, David, and Harry, there were some birds that were hard to ID because they passed at great distance, were only visible for a few seconds, etc. I had taken photos of some of these birds and now I have had time to take a closer look at the photos.

Among the birds there was one shearwater that appears to be a Manx Shearwater (photos below).

The characteristics in support of Manx are:
- very bright underparts, a clean underwing and especially a clean wingpit, with only a fine diagonal line along the wingpit
- the dark leading edge of the underwing is prominent and sharply defined
- a white crescent behind the ear-coverts (absent in Fluttering and Hutton's)
- the dark patches on the sides of the upper neck and breast do not join in midline of the throat or foreneck
- the wings are relatively long

As far as I know, there are no live records of Manx Shearwater from New Zealand waters, so any comments are very welcome.

Cheers,
Matthias

20171021-5MD_5072-3.jpg
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Photo 1. Note long wings and clean white underparts.

20171021-5MD_5073-3.jpg
20171021-5MD_5073-3.jpg (63.78 KiB) Viewed 1101 times
Photo 2. Note white crescent behind ear-coverts, long wings, and clean wingpit.

20171021-5MD_5074-3.jpg
20171021-5MD_5074-3.jpg (54.99 KiB) Viewed 1101 times
Photo 3. Note clean underwing with prominent and sharply defined dark edges.
Clinton9
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby Clinton9 » Mon Oct 30, 2017 9:58 am

By moult season, this is Manx in worn plumage and started to moult. Our seabirds are in fresh plumages and breeding now.
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David Riddell
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby David Riddell » Tue Oct 31, 2017 7:46 am

Matthias wrote:As far as I know, there are no live records of Manx Shearwater from New Zealand waters, so any comments are very welcome.

I'd buy that. I've seen Manx shearwaters on Skomer Island and this looks pretty good to me. Far more white under the neck and wings than I've ever seen on a flutterer, and that white crescent behind the ear coverts looks like a good character (some of my photos from Skomer don't show it, but when it's present it would seem to separate Manx from fluttering and Hutton's). Manx shearwaters have been picked up on beach patrols (some very nice photos of clean fresh specimens on NZ Birds Online - how many more decayed specimens have been misidentified as flutterers I wonder?), so they're obviously out there.
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RussCannings
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby RussCannings » Tue Oct 31, 2017 10:53 am

Very much a species on the rise in the north Pacific (presumed to be nesting in Alaska and/or BC) so worth keeping a careful eye out in the future. As Clinton pointed out, the most timing is another important factor in the I'D

Russ C
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sav
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby sav » Tue Oct 31, 2017 11:56 am

Another bird that I just don't know about (and that's getting to be a depressingly familiar theme!).

I think the degree of moult is important and should mean that this is not a local bird. I'll admit to the fact that I've not seen Manx Shearwater in this stage of moult which will make the wings look really different, but I have seen lots of them and this just doesn't have the right ring to it. And I've seen them in October, and I don't recall there being any obvious differences to earlier in the year.

The most obvious thing about a "standard" Manx is it's distinctly "black and white" appearance. And wear will change that of course, but this one looks very brown. I think the ear coverts crescent isn't as distinct as it should be, maybe because the dark semi-collar isn't strong enough.

The underwing pattern is wrong as well. I think there should be a more extensive trailing edge to the secondaries.

All of this might be explained by wear and moult. There are other species that live closer to NZ than Manx, many of which we know virtually nothing about.

It's all extra hard when the only evidence is after-the-fact photos and no feel for what the bird was like in the flesh.

Another one for the "too hard" basket?

regards
Sav Saville
Wrybill Birding Tours, NZ
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David Riddell
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby David Riddell » Wed Nov 01, 2017 10:03 am

Here's a picture of a bird that I saw on Skomer Island (back in June 1995, this is a photo of a photo from our album of the trip). It's rather over-exposed and a bit faded I'm afraid, but you can see that the crescent behind the eye is even less obvious than on Matthias's bird, and there is very little in the way of a semi-collar. I can't claim much experience with this species (basically two nights) but I think this shows the species has a degree of variability. On the other hand Sav might be right about the brownness, and I'm also wondering now about the sharpness between the dark face and white chin, though maybe that's a matter of exposure and graininess. Thinking about geographically closer species, I guess the obvious one to consider is Newell's shearwater (sometimes regarded as a subspecies of Manx) from Hawaii. Matthias's bird looks like it might have the very pronounced white flank patches behind the wings that Newells have, but again the face markings don't look like they're sufficiently clear-cut. Wikipedia says Newell's shearwater "belongs to a confusing group of shearwaters which are difficult to identify and whose classification is controversial." Very true I think.
Manx shearwater Skomer Island June 1995.JPG
Manx shearwater Skomer Island June 1995.JPG (199.91 KiB) Viewed 848 times
Matthias
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby Matthias » Wed Nov 01, 2017 11:50 am

Thanks for your thoughts!

Even fresh birds apparently can look brown in strong sunlight, see e.g. here. Worn/moulting birds seem to be browner in general. There is a picture of a worn individual in heavy primary moult in Ryan 2017 Guide to Seabirds of Southern Africa which is very pale (much browner than the Gisborne bird). This bird also shows a much more washed-out semi-collar which makes the ear-coverts crescent less distinct. There is a photo of a vagrant bird taken off California from a similar angle with a washed-out collar that looks almost identical to the Gisborne bird.

1/2 (too many URLs for one post)
Last edited by Matthias on Wed Nov 01, 2017 1:08 pm, edited 2 times in total.
Matthias
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby Matthias » Wed Nov 01, 2017 12:06 pm

The width of the trailing edge seems to be variable. This website has photos of Manx Shearwater from Great Britain that illustrate the variation in crescent, semi-collar, and trailing edge. It also shows birds with darker faces that contrast with the rest of the head and the white chin, here and here. This bird is photographed from a similar angle and the structure/jizz looks practically identical to the Gisborne bird.

I think Newell's and Townsend Shearwater are supposed to show more black in the undertail coverts. The Gisborne bird has a very white undertail.

Thanks for the interesting discussion!

Cheers,
Matthias
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RussCannings
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby RussCannings » Sat Nov 11, 2017 3:12 pm

Hi all,

Over the past few weeks I have been circulating photos of this bird to seabird experts in the Pacific and Atlantic regions as well as on a few Facebook ID groups. In general the reaction has been fairly positive for Manx, however often with the reservations regarding the photo quality or a lack of experience with other confusion species (e.g. Fluttering/Hutton's Shearwater). I am still hoping to hear back from some key people but below are a selection of some of the ‘expert’ reactions:

Alvaro Jaramillo (Author of “Birds of Chile” & California pelagic expert: “Looks like one to me, but I do not know the variation in local NZ species, having never been there. But structure and plumage are perfect for Manx.”

Robert Flood (One of the most active world seabirders): “the dark axillary markings are OK for Manx, though only a small minority of Manx that I've seen show the same pattern with this much dark. Fluttering of course typically has more and denser markings in the underwing. Primary moult late October is presumably OK for Manx (not well known since they moult after arriving in the non-breeding range late southern fall) and is at odds with adult Fluttering that breed from October/November. Other plumage characteristics are OK for Manx as far as I can see. The photos don't permit accurate judgement of structure (e.g. how much foreshortening of the bill) and I have no idea of size (e.g. was it seen with Fluttering Shearwater).”

Bruce Mactavish & Michael Force (The former, a Newfoundland birding guru, and the latter, an experienced seabird surveyor in the central Pacific): Both conceded that the bird had several characteristics of Manx but were concerned about the pale underparts—particularly the thin dark leading edge to the underwing (Secondary coverts)--interesting when compared to Robert's feelings. They also felt the angle made jizz judgments a little problematic but neither could offer any alternative IDs, citing unfamiliarity with NZ shearwaters.

Rohan Clark (Co-author of the new “The Australian Bird Guide”): “I think it looks good for Manx with one caveat....the bird does look a bit thick-necked....perhaps this is just a brief postural thing, partly because the bird is banking away?? Otherwise, white undertail coverts, white saddle bags, narrow diagonal underwing bar and dark primaries and secondaries in an otherwise clean white underwing, rather diffuse gradient between dark neck sides and white undersides, and obvious narrow pale crescent behind the eye seem to tick all other boxes.”

Alex Berryman (A keen pelagic birder from the UK): “Wouldn't want to confirm 'beyond doubt', I'll have a proper look through this later, but plenty of experience with Manxies (the go-to shearwater in the UK!), and this looks good. I can't add much to what Rohan has said re. features - the thick neck is always misleading on these, I've seen some with Little-type proportions in the past! We're always on the lookout in the UK for any shearwater that stands out or could be something different, this wouldn't catch my eye”
------
Of the 30 or so people who have commented on this bird either in private or on public Facebook forums, only two people (Both on Facebook Bird ID groups) have ventured an alternative hypothesis to Manx Shearwater. One commenter felt it was a Little Shearwater based on the thick-necked look and “more pronounced black tips to the primaries” while the other felt it was likely a Fluttering Shearwater based on “headshape and jizz”. Conversely, a significant number of commenters/responders felt it was okay for Manx, and around 40 people “liked” my Facebook posts inquiring whether or not this could be a Manx. Whether or not this constitutes an affirmation of the ID is unclear, however many of these “likers” are experienced seabirders who presumably would have offered a counter-hypothesis if they disagreed with the Manx idea.

I think it’s fairly safe to say that the bird in question is NOT a Little Shearwater (or related complex), simply based on the wing and bill proportions. Therefore, given the pale underparts, particularly in the undertail, it seems the only reasonable possibilities are Manx or Fluttering Shearwater. Fluttering Shearwater is undoubtedly the more expected species at this location so must be ruled out for the Manx ID to be clinched safely. Furthermore, the ‘un-Manx-like’ features (for lack of a better term), need to be justified in a more convincing way than the ‘un-Fluttering-like’ ones can be. Below I break down the problematic features and try to justify them for each species.

How could it be a Fluttering Shearwater if…

The subhumerals (armpit triangle area) are so pale? Well there is some dark colouration there, particularly on the right wing, but maybe a worn bird could be paler here
It’s in primary molt in Oct? Birds do weird things, and sometimes birds moult at the wrong time, so this must just be one of those exceptional birds.
It has a white ‘hook’ behind the eye? Facial pattern and amount of brown on the face varies in Fluttering Shearwater. This bird would be on the pale end, so it’s just a coincidence that the pattern matches some Manx.
The feathers behind the eye look black? This photo is from an awkward angle, so it could just be a trick of the light

Okay, but how could it be a Manx Shearwater if…

It’s in New Zealand? Seabirds get around, and Manx Shearwaters are northern hemisphere breeders that disperse to southern oceans in austral summer; they get around and NZ has several beach-wrecked records. Steady increases in numbers off Alaska could mean a growing Pacific population worth looking out for in our summer. This bird was around the continental shelf, which is not exactly Fluttering habitat either
There are darkish feathers in the lesser coverts on the underwing and a thin underwing bar? This pattern is actually not even at the dark extreme for Manx (Around 30% have darker lesser coverts than this bird, and the thin bar occurs in roughly 10% of birds)
It doesn’t look ‘black-and-white’ enough? This is a molting bird viewed in bright sunlight. As the photos below illustrate, it is not unusual for Manx Shearwater to appear brownish on the upperside. To be fair, the upperside colouration is hard to judge in all of these photos, and some might even call it more blackish than brownish…brackish?
The bird appears to have a slightly different pattern in the underwing of each wing? This perhaps hard to accurately judge based on the angle, but perhaps this would not be inconsistent with a bird in moult
The white ‘hook’ behind the eye is not very pronounced? Firstly, this bird is banking away, which doesn’t give us a full side-on view of the face, but also given the bright light and its molt condition, this is well within the range of variation for Manx (See photos below). Also notice strong blackish tones behind the eye despite strong sunlight
It’s in moult? That’s actually a strong piece of evidence to show this as a non-breeder. Manx typically moult Sep-Nov so this is right on time.
There are all sorts of other similar shearwaters in the world? All other related species (e.g. Newell’s, Townsend’s, Black-vented, and Yelkouan) have dusky or black undertail coverts which this bird clearly does not.
•It looks very bull-necked and perhaps short-billed? I think the bill looks just fine, with any perceived shortness resulting from the angle of the photograph (the bird is flying ahead and banking away from the camera). As for the thick neck, this could be a posture-related thing (as suggested by Rohan Clark above); but also keep in mind that Manx is a chunkier bird than Fluttering so this doesn’t support that species either. I don’t think it’s a Little Shearwater as the bill is too long and the wings are the wrong shape (not to mention the underwing pattern).

This photo (of a single bird) seen off California in September, illustrates how moulting Manx Shearwater can look brownish and have a more indistinct facial pattern. Obviously it has a different underwing pattern but one can easily find photos online showing bars such as the Gisborne bird (See Matthias's previous posts)
manx.PNG
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This photo, taken from NZBirdsOnline, shows two Fluttering Shearwaters in moult. From searching around online, this appears to be a fairly typical look for Fluttering in this stage of plumage. Note the darker underwing and collars compared to the Gisborne bird. It should be noted that juv/imm Flutterings also typically show fully brown subhumerals.
flsh1.jpg
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So it seems clear from looking at a variety of photos online and speaking with experienced seabirders, that these birds are variable, and this--no doubt--makes for a challenge. However, when looking at all the features holistically, it seems difficult to say this is NOT a Manx Shearwater, and equally so to prove that this IS a Fluttering Shearwater. If there is another realistic possibility, or if any of my statements above are inaccurate or misleading, I would love to hear about it.

Please continue to voice your doubts, concerns, or support below. #learningaboutbirds

Russ C
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sav
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Re: Gisborne pelagic (Oct 21) addendum: Manx Shearwater

Postby sav » Sat Nov 11, 2017 5:35 pm

Hey Russ, Mathias,

I can't disagree with anything in the summary by Russ. Except to add that it is equally difficult to prove it really is a Manx!

There is one thing missing in the puzzle for me, and that is what it looked like in the flesh? Did it have different jizz to Flutterers? Fly differently? Size difference?

cheers
Sav Saville
Wrybill Birding Tours, NZ
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