Friday, 27 April 2012

Passage Terns

25th April - a very wet morning giving way to heavy showers in the afternoon saw a large movement of terns and Little Gulls along the Severn/Wash fly way, with many seen in our region, especially during the afternoon and evening.

I got a text from Dave P around midday saying he had 11 Arctic Terns on the pit.  I couldn't leave until after lunch - which was not going to be long, but got another text shortly afterwards to say that they had gone - birds were obviously on the move.

I arrived at about 12:30pm and sat in the car while a heavy shower went through and then joined a damp Dave P and Mick M at the western bench - a brolly was essential birding gear in this weather!  We scanned the pit and southern tree line looking for birds arriving off the river.  At about 12:50pm I noticed a small dark tern flying along the southern bank of the pit towards the SE corner - a lovely summer plumaged Black Tern that had obviously just arrived!  It proceeded to flying backwards and forwards along the eastern side of the lake.  Whilst this was going on, texts were coming in all the time about Arctic Terns and Little Gulls being seen in good numbers arriving and departing various sites just to the north of us.  Optimistic of joining in with this movement, we kept watch until the school run beckoned at 3pm, but no further joy - perhaps just a little too far south from the fly way.  A tight flock of 5 Common Terns was seen to descend to the lake and continue high eastwards, so they were obviously moving as well.

Mid afternoon, I noticed a pale alba wagtail working its way along the near bank of the spit.  I'm never too quick to call White Wagtail, as I've seen quite a few pale-looking female Pieds in the past.  On scrutiny, however, this bird showed pale, clean flanks below the brownish tinged wings, a pale grey smudge to the sides of the breast with a white line bordering the black bib, a clearly demarcated black cap from the pale grey mantle and more importantly, the pale grey extending to the rump and upper tail - so a classic White Wagtail.

Later, a 3cy gull caught my eye, that showed a very dark grey mantle, approaching LBB Gull in colour.  I put the other observers onto it and we pondered its ID.  I thought that it was probably a Yellow-legged Gull, though it's getting a bit late for them.  I grabbed a couple of record shots when it walked out on the spit, though the mantle shade appears lighter in these than it did in the field.  The head and bill shape look good for YLG - the bill being particularly broad based and blunt-tipped looking very yellow with the large red gonys spot showing through the black terminal band.  It also shows a reddish orbital ring and some red on the gape line.  On the closed wing, the outer greater coverts look a little Herring Gull like, showing evenly spaced spotting, though the inner coverts are more diffuse - this shows better on the open wing and is also better for YLG.  Many of the juvenile median coverts had been replaced with grey. The tail was white contrasting with a neat black tail band and the grey mantle and the under tail coverts had just a few sparse spots around the sides.  The legs were beginning to show a pale yellow colour, particularly on the front of the tarsus, which just about shows on the photos.  The eye was dark, but it is immature and I have seen older YLG than this show a dark eye.  In flight, the wing looked OK for YLG and also showed a smaller primary 'window' than I would expect on Herring Gull. So I concluded that this was indeed a 3cy Yellow-legged Gull, but I'm open to comments.

Grey mantle appears lighter than in the field

Open left wing just showing - note the yellowish legs starting to appear

Reddish orbital ring a red in the gape line
The gulls flew at about 2:30pm and Dave P commented 'I've got a Yellow-legged Gull'.  I assumed he meant the bird above, but in fact he had found a cracking adult bird - another unexpected bird.  It was more distant and in the poor light, a blurred record is below.  It had incredibly yellow legs and was a full summer bird, though the bill had a small dark line towards the tip, which was also pale.  It was a big bird (compare to the nearby LBBG), so probably a male.

There were probably around 100 LWHG on site - many immatures - and judging by the birds above and the number of different colour-ringed birds being seen, many are moving through the site.

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