I spent several hours at Willington Gravel Pits on Sunday morning (25th February 2018), in the hope of seeing the regular Great White Egret. After some time, the bird appeared briefly on and off but never close. There was also a good flock of Curlew (16) and Wigeon (67), a single Little Egret, several Shelduck and the usual water birds I would expect to see at this time of year, what I call “The Usual Suspects”. Shortly after arriving in the hide I watched a female Pintail drop in, along with a pair of Gadwall. Then a small flock of large gulls arrived and dropped in on one of the islands in front of the Hide. I began to give then a closer inspection and one of the birds stood out and I suggested to others in the hide that they should take a look at this bird. I remarked that I felt it looked like a 3rd winter Caspian Gull and I began to take a sequence of photographs. Shortly after bathing, the flock took off and I got on to another bird in flight, initially thinking this was the bird I had been looking at. Upon showing people the photos, nobody queried the ID and we all thought that the bird we had been watching was a Caspian Gull. The following photographs show the two birds I am referring to.
Once I had the pictures on the computer, I could look at both birds in more detail. I immediately began to have some nagging doubts and immediately noticed that the bird in flight was a different gull, but what was it?
I have spent the past few days looking at many images of Caspian, Yellow-legged and Argentatus Herring Gull. In my humble opinion this group of gulls are by no means easy to identify, unless of course you have a classic bird at close quarters. There were anomalies on both gulls and the initial bird I thought to be a Caspian, had an adult head and bill but with a distinctive pale eye. I was clearly confused and I began to get suspicious about this bird in particular. I have also discussed both birds at length with one of our local “Gull Watchers” and someone who I have a good deal of respect for his gull identification and also a friend in Bulgaria and I am grateful for their constructive comments.
The bird below and in flight is in fact a 3rd winter argentatus Herring Gull. Note the large obvious pale grey “window panel” in the wing. There are only two distinct grey tongues at P6 & P5. The grey tongues in Caspian are more extensive into the primaries and show what is called a “Venetian Blind” effect. A pale grey saddle (wrong colour grey for Caspian Gull), clean white rump and a slight tail band. The slightly dark eye is apparently not an issue for argentatus Herring Gull. The secondary bar is also very pale and is usually much darker and contrasting in Caspian Gull.
Herring Gull – race argentatus – 3rd winter – Willington Gravel Pits, Derbyshire – Tony Davison©
The following images show the bird I initially thought was a 3rd winter Caspian Gull. I now believe this bird is most probably a 3rd winter argentius Herring Gull. Any potential 3rd winter Caspian Gull showing such a pale eye needs treating with caution and is likely to be a Herring Gull. The tertial pattern is wrong for Caspian, as are the markings on the wing coverts and secondaries. The bird shows very short pink legs, Caspian is much longer in the leg. The bottom picture shows both the birds in discussion side by side. What really did throw me was the clean white under-wing of this bird. I have always been advised that this is a feature of any immature Caspian Gull? Just to throw a further spanner in the works – I’m sure I can see grey tongues in the bird’s left wing at P6 – P9 ( a feature of Caspian Gull) There is a complete black band on P5 and a small black patch on P4, which I think is a feature of 3rd winter Caspian Gull? However, I cannot see a white mirror on P10. The overall general appearance of the bird, along with proportions, shape and colours of head, bill and eye, were what lead me to believe this to be a Caspian, but there are other features that don’t seem to fit. Could this bird therefore be a hybrid? Any constructive comments would be gratefully received.
Left – 3rd winter argentatus Herring Gull –
Right – 3rd winter argentius Herring Gull