This blog is about my birding exploits, which mainly take place in the Weymouth/Portland area, in Dorset. Will also include stuff from elsewhere, plus some other critters too. Hope you enjoy. All photographs are © Brett Spencer, unless indicated otherwise. The above image is of a Siberian Rubythroat, taken in Holland in 2016.

Saturday, 20 June 2015

The Maiden Castle Snow Bunting

On the 17th March 2015, a Snow Bunting was found at Maiden Castle, near Dorchester. The bird remained till 21st March. 

There are only a handful of inland records for Dorset, so this was an excellent find.

I'd been told it was a cracking bird going into summer plumage, so thought it worth a look. I saw it on 21st March and sure enough, it was indeed a stunning bird, but not the summery plumage I was expecting. It was, in fact, in winter plumage.

I could immediately see that it was a particularly fine male, due to the extensive amount of white in the wings, but on seeing it in flight, the striking white rump really did catch my eye. I then realized that this bird was showing characteristics of the form P.n.nivalis from Fenno-Scandia/Greenland. Other features showed me that this was a 1st-winter bird.

This got me to thinking about the differences between P.n.nivalis and P.n.insulae, the latter from Iceland, the ageing of Snow Bunting and the status of the two forms in Dorset.

The male Snow Bunting at Maiden Castle. The extensive white in the wing, with mostly white greater coverts, show that this is a male.

The white of the rump is obscured by buff feather tips and summer plumage is attained by feather wear. When the pale feather tips have worn off by the summer, this bird will be black and white. The white rump is the key difference between P.n.nivalis and P.n.insulae, but note also the amount of buff on the head, breast sides and flanks on this and the images below. The underlying colour of the rump of P.n.insulae is black.

On this and the image above, note the pointed tips of the tail feathers, the thin buff/white fringes to the tertials which help to age it as a 1st-winter bird. Adults would show rounder tips to tail and broader fringes to tertials. 

The extensive amount of black in the primary coverts also help age this bird as a 1st-winter.

1st-winter male Snow Bunting of the form P.n.insulae at West Bexington, 7th February 2013. Compared to the Maiden Castle bird, note the more extensive buff colouration on the head, breast sides and flanks. 

The West Bexington bird again. Although obscured by buff feathers tips, the underlying colour of the rump was black. the pointed tips to the tail feathers show this is a 1st-winter and the mostly white greater coverts show this is a male.

The status of P.n.nivalis in Norfolk from ringing studies shows that the occurrence of the form is the scarcer of the two, though in some winters can make up 50% of the wintering flocks. In some winters though, there are very few indeed. Being that Snow Buntings are annual visitors to Dorset, they only occur in small numbers and as a result, I believe that P.n.nivalis is a rare visitor to the county. Good photos will help you racially assign future male Snow Buntings in Dorset. Start by sexing and ageing the bird correctly before racially assigning any individual. Females are much trickier, but ageing and sexing correctly, followed by photos of the spread upperwing showing the amount of white on the visible part of the 9th primary (40% or less in P.n. insulae and 60% or more in P.n.nivalis) are critical to racially assigning.

So, next time your watching a Snow Bunting performing well, take the time to really study it, I'm sure you will find it very rewarding and educational, as I have.

1 comment:

Peter Moore said...

Educational stuff - well put together.