ML608540178

Age

Not specified

Sex

Not specified

Observation details

Immediate comments on field A super large Skua. First saw in the distance, a huge Skua with prominent white flashes and two smaller birds behind it. Clearly South Polar/Brown. Then it sat down and allowed us to get really close :) Incredible looking bird. Robust and with a very heavy bill. Later comments from consultation Identified as Brown Skua after consultation with various people (some yet to come). All comments on the ID below. Thanks to Praveen, Dipu (India), and Ramit, Ben, Vincent Mourik, Peter Vaughan (Australia), and Moditha, Gary Allport (Sri Lanka) for their comments. Dipu Had a look at the available images. The bird seems to be completing its primary moult (P10 is growing), legs and beak is all dark indicating an adult/near adult bird (This combination, along with lack of scalloping eliminates Great). Some photos indicate bleaching in feathers, so, colour may be a bit difficult to gauge. The beak size is really large, larger than typical SPS and in Great/Brown territory. The toes almost reach the tail tip, another supporting feature for Brown. One thing that I see is a smallish looking head, lacking the butch feeling a typical Brown gives. Otherwise, a good candidate for Brown. Moditha The very robust look, stout bill and pale fringes on the upperparts suggest Brown Skua. Gary Bill weight alone points to Brown. Vincent Mourik - A quantum physicist who studies SP Skua and Brown Skuas in Australia After looking at final photos - Excellent series of pictures. It's a definite brown in my opinion, adult type, most striking is the mottling throughout the back characteristic of brown rather than SPS. After looking at initial 4 photos - Without knowing location I instantly thought worn Brown. Structure I find tough I use it more as supporting mark when judging pictures. The back has some mottling in it more consistent with Brown. You can see from the contrast in the head that the fresh feathers are dark brown. I allege that any paleness in the underparts is caused by worn body plumage yet to be replaced. Primary moult is almost finished. If any old secondaries remain (not too sure there are any) it would be useful to investigate them for juvenile tips, however, primary moult timing is incompatible with juvenile. Meaning the contenders are older dark morph South Polar or Brown. Or a hybrid. But treating it probabilistically that introduces a few percent multiplier... Either way whoever saw this needs to gather all pictures and do careful analysis. I'm just giving you first impression. I'd be happy to help down the track and study in depth and give input but ideally that's at the point where all pictures are gathered. What's the exact location? There's nothing in the seabird tracking database near India brown skua wise. But some projects are not in there. 2018 Delord et al polar biology is probably the most relevant study, no track real close to India it seems. But I do vaguely remember a paper summarizing vagrant skuas in India that suggested at least one Brown. While tracking studies etc are by definition not useful when considering vagrancy, of course it should be considered. I think South Polar Skua has a higher likelihood to end up in the tropical Indian ocean towards India etc than Brown. This is mostly based on the overall observation that Brown's don't migrate as extreme as south polar, and its somewhat supported by the tracking work. Meaning that I guess Brown in India is supposed to be the rarer species, but I suppose all Skua sightings are rare there. What I don't like for South Polar in this bird, and what me mainly sways towards Brown, is the presence of a bunch of broad light tips on the back, creating a mottled appearance more compatible with Brown. But its not very strong, and perhaps it could be attributed to wear in South Polar. I'd have to do a deeper dive then. Another thing I don't like for South Polar is that the worn body feathers seem to be straw yellowish. I find this to be rather common in Brown. What I don't like so much for Brown is that the bird's overall colour tone is a bit cold, not warm. I am not bothered at all by the apparent contrast between upper/underbody, nor the presence of a pale nape. First feature is commonly present in worn body plumage of Brown, second feature is widespread in both species and useless for ID. I'm still leaning more towards Brown. But there's ways this bird can turn into a South Polar. I think its essential to gather all photographs, not throw a single one out. And do a deep dive into the details of the plumage. Its necessary anyway given the rarity of either taxon in India. On structure and bill - both should be considered. But its also very variable, and judging it in the field is highly subjective. There is overlap between both species in all dimensions, its the tails that overlap. So to really utilise morphometric arguments one needs measurements. I would not be surprised if one day something can be worked out regarding wing structure, as I suspect South polar is slightly lankier. But its not been done yet so we can't use it as yet. I've seen pictures of South Polars with honkers of bills but that's out at sea. In flight, often with the head feathers dressed differently than your typical colony resting picture and people tend to take that then for evidence for Brown but I think its just different posture. Also moult of the head feathers can affect this. I'm happy to comment on the bill on this bird: I find its appearance to be very deep, but kind of average lengthwise. On the white on base of primaries - white bases: again, unreliable. Huge overlap between the species. In both species, on average, older birds have more white, females have more than males, south polar more than brown. But lots of overlap really not useful other than supporting the narrative once other features clinch it. Peter Vaughan Bill looks relatively deep, but also very full-chested and thick necked cf SPSK. Looking at it now I'm leaning well towards BRSK. The feathers look quite work giving a contrasty look, but they're still somewhat streaked and warm-toned (I.e. the base colour and texture looks brown). I also reckon the wing flash extent is partially a facet of worn coverts making it just that bit larger. Jeff Davies (author, Australian Bird Guide): (Tentative) Looks like straight forward Brown on my phone also. Away from home in Wet Tropics, will save images when back home mid October.

Technical information

Model

NIKON Z 8

Lens

AF-S NIKKOR 500mm f/5.6E PF ED VR

ISO

640

Focal length

500 mm

Flash

Flash did not fire

f-stop

f/7.1

Shutter speed

1/1600 sec

Dimensions

849 pixels x 1273 pixels

Original file size

298.68 KB