Friday 9 August 2019

Summer Gulling, having a Caspian blast

3 juvenile Caspian Gulls were present amongst several hundred large gulls on the rising tide (Thames) during the afternoon of Sunday 04 August 2019 around Erith Pier, London. Loafing (no pun intended) on the shore on the incoming tide and attracted by the sliced offerings from dedicated gull watchers most of the gulls on show were immatures. These included juv. Herring Gulls now present on the river with over 20 juv. Yellow-legged Gulls, some flying around like 'greased lightning' in a feeding melee. Several Lesser Black-backed Gulls added to the plumage conundrum and Black-headed Gulls, Great Black-backed Gulls and the first Common Gulls of the autumn were noted, including a smart fresh juv. Common.

Arriving on site early afternoon and some of the country's top gull watchers were present, namely. The first 'Casp' had just flown in, a small dark plumaged bird that seemed to have an injured leg. It quickly relocated to the adjacent jetty where it was reluctant to move until forced to shift further up the jetty by the covering tide. Concerns were raised of its welfare, or was it just very tired, fresh in from the continent? Later it perked up and would compete with others for the loaves on offer. It stayed more or less with the gull flock throughout the rest of the watch. A second bigger bird flew in much later and stayed only for a short while, whereas the third bird seen shortly thereafter was again different to the other two and stayed to the close of play. All had distinct plumage traits of this taxon and varied in appearance such as their size (this would point to Bird 1 = female and Bird 2 = male) and in their state of post juvenile moult.

Probably seen around 40 Caspian Gulls in GB infrequently over the last 20 years, but this being only my second time of seeing juv. Caspian Gulls, the first was the aggressive youngster present back home at Ingbirchworth Res, South Yorkshire in July 2016, a German ringed bird from Brandenburg (yellow ring X215). Given my lack of frequent sightings of this species I'm till getting used to the features of this wonderful Larid, and I show the photos below without detailed analysis. However, I would like to draw the reader's attention to an excellent Birdguides article written by one of the observers (Josh J), an article focusing on the identification of juvenile Caspian Gulls. Whilst there are lots of top texts available on Caspian Gull identification I would like to think that the penny was starting to drop when reading this article on the train en route.

Summer Gulling, was certainly a blast! Tell me more, tell me did the scapulars and greater coverts look right? Tell me more, tell me more did the underwing look more or less white? 

What I will say concerning the identification of the birds on show is that in my humble opinion and not deviating from a 'happy path'- the tail, upperwing and scapular patterns on all three birds looked good from a recollection of the literature, and the underwing looked to be within tolerance. Looking at the structure, the different size and different state of moult of the three added to the fun (or stress) in naming such gulls. But simply, put all the above to one side, the most critical aspect in identifying immature large gulls will always lie with the observer's experience of the plumage and taxon. Enjoy.

Throughout the session the 3 'Casps' were called out as Bird #1, Bird #2 and Bird #3. Should we give familiar names, how about Sandy and Danny for the first two?

Caspian Gull (Bird #1)

Caspian Gull (Bird #2)

Caspian Gull (Bird #3)

Yellow-legged Gull

With thanks to the help from all birders on site with the gull ids throughout, much appreciated. More photos at Latest UK Bird Photos.

For excellent images of the Caspian Gulls present please see the twitter feeds of Rich B, Dante S and Josh J plus the blog post from Josh.