Skua, Broughty Ferry, Scotland. (1 Viewer)

Had a Skua fly over me this morning on the east coast of Scotland, at Broughty Ferry, Dundee. The bird appeared from the west over the north bank of the river then circled twice just above me, and over a large group of feeding birds on the shore and just offshore in the river Tay estuary. It then headed inland to the northeast.

My first impression as it approached was a Cormorant until I lifted the camera, where I could clearly see it was a Skua. I called "Bonxie" to my pal, and took a few photos as it circled above. Looking at the photos later it appears to have a rather prominent central tail projection (this was quite noticable at the time also) and the bill doesn't look powerful enough for Bonxie.

The tail projection is the main feature making me doubt my initial ID, as I can't find a clear photo with one as prominent. Pomarine would be the other possibility, but as I've never seen one I have nothing to make a comparison with, other than illustrations/photos in books which when I try to work with them, end up confusing myself further.

Any opinions, folks?

Thanks

Baz

A few more photos...

Pretty sure it's a Great Skua, but wait to hear it from someone who is more sure of themselves!

Stonefaction said:

Had a Skua fly over me this morning on the east coast of Scotland, at Broughty Ferry, Dundee. The bird appeared from the west over the north bank of the river then circled twice just above me, and over a large group of feeding birds on the shore and just offshore in the river Tay estuary. It then headed inland to the northeast.

My first impression as it approached was a Cormorant until I lifted the camera, where I could clearly see it was a Skua. I called "Bonxie" to my pal, and took a few photos as it circled above. Looking at the photos later it appears to have a rather prominent central tail projection (this was quite noticable at the time also) and the bill doesn't look powerful enough for Bonxie.

The tail projection is the main feature making me doubt my initial ID, as I can't find a clear photo with one as prominent. Pomarine would be the other possibility, but as I've never seen one I have nothing to make a comparison with, other than illustrations/photos in books which when I try to work with them, end up confusing myself further.

Any opinions, folks?

Thanks

Baz

Click to expand...

This is indeed a Great Skua, with typical broad wings and prominent white wing-flashes, both these features ruling out Pomarine. The length of the tail projection is unusual, and very interesting for me to see, as I had a Great Skua with even longer tail projections, as long as the bill, past Flamborough Head on 27/10/11. I was amazed by that bird, so it is good to see your photos, showing a bird which isn't too far off mine with regard to the tail projection.

Cheers

Brett

Thanks, both. Brett, your thread about that bird came up at the top of the search results during my google search when trying to find a match for "Great Skua tail projection". On jizz alone, I thought my bird was a Bonxie - having seen quite a few of these over the past few years. I wonder if the tail projection could be a result of fresh central tail feathers growing back in during moult and being more prominent than the older feathers either side, although the difference between your and my date of sighting maybe make this unlikely.

Stonefaction said:

Thanks, both. Brett, your thread about that bird came up at the top of the search results during my google search when trying to find a match for "Great Skua tail projection". On jizz alone, I thought my bird was a Bonxie - having seen quite a few of these over the past few years. I wonder if the tail projection could be a result of fresh central tail feathers growing back in during moult and being more prominent than the older feathers either side, although the difference between your and my date of sighting maybe make this unlikely.

Click to expand...

I'm sure it's not due to moult. The rest of the tail on both my bird and yours looks normal length for Bonxie. If the rest of the feathers were to grow so that there was no appreciable tail projection, the whole tail would be abnormally long. Also I don't believe the central feathers would be moulted out and grown back to full length before the bird had dropped any more rectrices. BWP gives the tail moult sequencs as t1-t2-t6-t3-t4-t5, so I can't see that the tail would ever appear like this due to moult.

Cheers

Brett

Moult was the only explanation that I could think of, other than it perhaps being just an uncommon(?) feature of some Great Skuas. I never thought to look up BWP. Will need to remember that for next time I have any moult sequence queries. Thanks again, Brett.

Hybrid?

I know that's meant to be a bit of lame possibility, but Great and Poms can hybridize I believe? (Isn't Pom meant to be a very recent hybrid result of two (unknown?) skua species anyway ... ? ).


And being a hybrid doesn't mean it would show features halfway betweeen the two in other respects of course ... although slim bill is mentioned. (And there's probably no way of ever knowing.)

The two central tail feathers extending out is fairly common in the Skuas I've seen when on foot across cape wrath. I thought at first they were dark phase arctics until I saw more together.

dantheman said:

Hybrid?

I know that's meant to be a bit of lame possibility, but Great and Poms can hybridize I believe? (Isn't Pom meant to be a very recent hybrid result of two (unknown?) skua species anyway ... ? ).


And being a hybrid doesn't mean it would show features halfway betweeen the two in other respects of course ... although slim bill is mentioned. (And there's probably no way of ever knowing.)

Click to expand...

Bonxies usually show a small projection

http://www.orkneyboattrips.co.uk/ESW/Images/Greatskuainflight.jpg

http://scillypelagics.com/GRSKz1.jpg

http://farm4.staticflickr.com/3306/5838917090_bd21600d07_z.jpg

http://2.bp.blogspot.com/-wTtWjWm29...yr4/s1600/Great+Skua_300412_BH_MD_DSC4230.jpg

http://www.stuartelsom.co.uk/copyrightphotos/Great Skua ~ Sagres, Portugal.JPG

http://www.adriandaveybirdphotography.co.uk/images/Great_Skua12-Shetland-june08-011.jpg

Thanks again, folks. I found a few photos when searching that hinted at a tail projection, - as one of the illustrations in Collins also appears to, but wanted to be sure of ID and none of the photos I found were as obvious as the ones Jane has posted. Every day is a school day.

dantheman said:

I know that's meant to be a bit of lame possibility, but Great and Poms can hybridize I believe? (Isn't Pom meant to be a very recent hybrid result of two (unknown?) skua species anyway ... ? ).

Click to expand...

Pomarine and Great Skua diverged from a common ancestral population, 'recent' only in terms of previous divergences from the original ancestral population of all skuas. Much more recent is the divergence of Brown, Chilean, Tristan and Subantarctic Skua from a common ancestor that itself diverged from Brown Skua, all taxa that inhabit the southern oceans; there, many individuals are not diagnosable because of the extent of pairing by individuals from different populations on widely-separated islands. My guess is that most of these taxa will 'harden' their identity with time, but of course external factors, such as rat infestations, could diminish or exterminate core island populations.

Pomarine and Great Skua do seem not to have lost the ability to interbreed, producing hybrids, but whether such hybrids remain fertile or whether the hybrid characteristics persist through subsequent generations is unknown. Generally, their breeding distribution types widely differ: Bonxies are mostly tied to fixed breeding sites (although individuals may not be) whereas Pomarines breed in whichever area has the highest lemming population. Opportunity to hybridise is therefore lacking for a vast majority of these birds. However, lemming populations appear to be in decline everywhere, due mostly it is suggested, to the disappearence of lengthy snow cover, thus preventing succesful breeding, and so it is possible that a successful and mobile top predator like the Pomarine may switch to an alternative diet that then may tie it to more fixed breeding locations, possibly nearer to Bonxie-land.

It's increasingly apparent that for many (but far from all) species-pairs that there is much more to hybridisation 'triggers', dominant-gene suppression and the persistence, disappearance or non-appearance of morphological traits than had been previously understood - the black/grey crow complex and the large white-headed gull complex are but two examples.
MJB