Monday, 2 January 2017

Gannet at Barns Ness, 31 Jan 2016

I reported this Gannet as a possible Cape Gannet and then I thought I had nailed the gular stripe and I was fairly convinced. After examining the images (all video grabs) I am now unconvinced and think this bird is a subadult Northern Gannet.

At about 11:00 am I picked up the Gannet as it was shearing low across the strong SW wind. Initial views were confusing as I thought I was looking at a bird just slightly larger than a Fulmar. With its bold and clean patterning I did not recognise it immediately as a Northern Gannet and thinking it was a smaller bird I thought about a Booby or Cape Gannet. It also seemed to be making almost no progress against the wind unlike the other Gannets I had already seen. In the 40 or so minutes that I watched it at this point it made almost no headway other than slowly drifting out and disappearing (with the benefit of hindsight I think it probably settled on the water). Barns Ness has constant streams of Northern Gannets passing by for most of the year but this bird's behaviour seemed distinctly unusual and wasn't something that I was aware of noticing before. At this stage however I was assuming that the bird was a subadult Northern Gannet but keen not to give up on a possible Cape Gannet I watched the bird as much as possible and tried to get footage. Handheld phonescoping at high magnification resulted is unwatchable footage but allows images to be grabbed.

The light was good and despite careful observation at no point could I see anything other than pure white coverts and fully dark flight feathers and tail. I knew that this was unusual for subadult Northern Gannet so posted some images to Twitter - at this point it was an idle tweet rather than any sort of identification but suggesting a possible Cape Gannet. I then had a look online and reread an old blogpost of mine and the BirdGuides ID article for Cape Gannet. Both of these (unreliable?) sources indicated that clean white underwing coverts is very strong indicator. At this point I decided to look for a gular stripe and was amazed when one of the first screen grabs showed what seemed to be an extensive gular! This I now think is an artifact - although it shows up on several of the images I think that it is a result of zooming into the image too far...

I then had to go and buy a phone charging cable and it was a couple of hours later before I was able to have another look for it. Incredibly the bird was still off shore batting against the wind. I put the news out and 3 other Lothian birders who were in the area saw the bird. Nothing further could be ascertained from these views plumage-wise but it was strange how it had only made about 1km progress in several hours - at no point did the bird actively feed (probably due to sea state). There was opportunity to see the bird in more direct comparison with other Northern Gannets and it seemed similar in size.

More careful review of the images shows the bird to be a Northern Gannet in my opinion - the secondaries are not extensive enough as a proportion of the upperwing so form too narrow a bar as mentioned by others on Facebook. The overall wingshape is also too long and angular in my opinion - I think that Cape Gannet would show a shorter wing overall.

So, in conclusion, a smart-looking Northern Gannet that fooled me into putting news out of mega...