Gull watching on the River Lune by Lancaster Tip

In recent years interest in the identification and taxonomic status of the so-called Herring Gull complex has steadily grown. While some official bodies (e.g. the BOU - the custodian of the British list) remain cautious, many birders across Europe have begun to regard Yellow-legged Gull (Larus michahellis) as a valid species, rather than simply the ‘southern’ form of Herring Gull. It is a regular visitor to Britain with large numbers appearing at favoured sites in southern England (e.g. the Thames Estuary and Poole Harbour) during July-November as a result of post-breeding dispersal.

In the LDBWS recording area the status of Yellow-legged Gull is ‘skewed’ by the annually returning adults at Arnside, Bazil Point/Glasson Dock and in the Dockacres area. Otherwise it is a relatively rare visitor with occasional records of adults, mostly from Sandside on the Kent Estuary, during July-September. The paucity of records from Lancaster Tip - probably the best site in the local area for attracting large numbers of gulls - is particularly striking. The few previous records from this site have tended to be during December-April as a result of increased coverage by birders searching for Glaucous and Iceland Gulls. In response to the apparent lack of scrutiny of the gulls on and around Lancaster Tip at other times of the year I decided to try and make regular visits to the site this autumn specifically to look for Yellow-legged Gulls.

An additional incentive for making these visits was a desire to improve my overall gull identification abilities in the light the recent upsurge in records of Caspian Gull (L.cachinnans) elsewhere in Britain. Within the last three years ground-breaking identification papers by Martin Garner and Lars Jonsson have alerted birders to the distinctiveness of this gull. Depending on what you read, Caspian Gull (or Pontic Gull) is considered to be either a valid species, the nominate race of Yellow-legged Gull or simply another taxa within the Herring Gull complex.

While Lancaster Tip itself attracts large numbers of gulls these tend to be somewhat distant and difficult to view. Much easier to study are the gulls which gather on the adjacent tidal section of the River Lune at low tide to bathe in the river and loaf on the nearby mud. Since early August I’ve made 42 mostly ‘lunch time’ visits to view this area - mainly from the south side of the river. These observations clearly suggest that Yellow-legged Gull has been under-recorded in at this site in previous years. Between 3^rd August and 1^st December at least 9 (possibly 12) different birds (distinguished on the basis of age, intensity of leg colour, bill markings and degree of head streaking) were seen on 14 dates, including 3 different adults on 18^th August.

By late August I had also begun to notice small numbers of colour-ringed birds amongst the hundreds of gulls spread along the edge of the river. These included adult Herring, Lesser Black-backed and Great Black-backed Gulls, plus juvenile, 1^st summer and 2^nd summer Lesser Black-backed Gulls from the colour-ringing scheme organised by Dave Sowter. This scheme involves the colour-ringing of juvenile Lesser Black-backed Gulls from the colonies on the Ribble Estuary, Tarnbrook Fell and South Walney. These birds are ringed with either a green ring with a single white letter or a black ring with yellow lettering on their left leg and a BTO ring on their right leg. The birds with a green ring were ringed as juveniles in 1997 and the white letter denotes which colony birds originate from - R (for Ribble Estuary), T (for Tarnbrook Fell) or W (for South Walney). So far there have been three sightings on the Lune of birds ringed at Tarnbrook in 1997, but none from the Ribble or Walney. The fact that these colour-rings do not identify individual birds means that the three sightings - 15^th September, 3^rd November and 16^th November - may refer to three different birds.

In 1998 and 1999 the study has used codes to identify individual gulls. These consist of the colony code (R, T or W) followed by a single digit number and two letters (e.g. T7HD, W0AV, etc.). Between late August and early December about 29 of these gulls have appeared on the River Lune. It is difficult to be more precise about the total number of these birds as reading the complete code on some of the rings has not been possible due to distance, duration of view, light conditions, etc.

From the observations made a few interesting points have begun to emerge. Firstly, it is evident that birds from all three colonies occur on the River Lune.  Of the overall total of 29, 14 originate from Tarnbrook, 10 from Walney and 5 from the Ribble. One of the aims of Dave Sowter’s study is establish whether gulls from these colonies use common feeding and roosting sites - clearly the Lancaster Tip area is of some significance in this respect. The appearance of 1998 ringed birds in 1^st summer plumage (e.g. T1DZ, T7HD, WOAV and W2BU) during this autumn is also of interest. Evidence from recoveries from Dave Sowter’s and previous ringing schemes indicate that the vast majority of locally bred Lesser Black-backed Gulls migrate south during their first autumn and remain in the wintering areas of Iberia and Morocco until they are mature enough to breed, perhaps in their fourth year. These observations suggest that a small, but perhaps increasing number of immatures are either over-wintering or returning earlier than they used to. Possible reasons to account for this apparent change in behaviour include the increased availability of food as a result of landfill sites and/or global warming (D. Sowter, pers. comm..).

As Dave Sowter’s scheme is on-going, tracing the details of these gulls is straight-forward. The same cannot be said of some of the other colour-ringed gulls seen on the River Lune in recent months. Despite one notable success outlined below, many of these birds appear to derive from various university research projects for which the original ringing details are either ‘lost’ or untraceable due to the gulls outliving the researchers’ interest in them!

The notable success came after six weeks of staring at the locally reared juvenile Herring and Lesser Black-backed Gulls, in the hope of finding a juvenile Yellow-legged Gull. On 13^th September I located a bird standing in the River Lune which seemed to possess the requisite combination of features - a jet black, heavy blunt-tipped bill contrasting with a strikingly white ‘face’, dusky eye-patch, dark brown tertials with narrow pale fringes and dark outer greater coverts. In addition, the bird had a number of fresh first-winter scapulars - unlike any of the nearby juvenile Herring and Lesser Black-backed Gulls. After standing in the river for about 10 minutes the bird finally wandered out onto the mud and I was amazed to see a large white ring with the code 161C on its right leg and a metal ring on its left leg. As far as I was aware this didn’t correspond with any on-going British colour-ringing scheme. However, the fact that the bird was clearly a juvenile meant that it must have been ringed sometime within the previous 3-4 months and I was reasonably confident that it would prove relatively easy to trace.

Yellow-legged Gull colony at Lagune des Imperiaux in the Camargue on 12^th May 1999. It thus represented the first confirmed record of a juvenile Yellow-legged Gull in the LDBWS recording area and the first British record of a French-ringed juvenile. The fact that this gull was ringed in mid-May was also significant - it was almost two months older than the Lesser Black-backed Gulls ringed as part of Dave Sowter’s study. This helps to explain why it had already begun to moult into 1^st winter plumage by the time it reached Lancaster in mid-September.

Despite this success, by early October my attempts at tracing the origins of some of the other colour-ringed gulls seemed to have ground to a halt. I decided to contact Chris Mead - one of the ‘elder statesmen’ of British ringing - for any suggestions as to who else I could contact. His reply was illuminating, if not quite what I had hoped for:

“Colour ringing of gulls is a nightmare. It has been going on for 40 years and many marks are both repeated and very like previous ones. Large numbers of old schemes are VERY unlikely to have rings still on the birds. If they have survived, the colours may have faded and changed!”

Fortunately a couple of days later I received a letter from Dr. John Coulson, recently retired from the Department of Biological Sciences at Durham University. He confirmed that three of the adult Lesser Black-backed Gulls that I’d seen at the River Lune originated from a Durham University scheme. They were captured by cannon netting at Lancaster Tip in early 1992 and ringed (white ring on right leg, BTO ring plus combination of three colour rings on left leg) as part of a study of the Tarnbrook Fell gull colony. Interestingly the Durham researchers never actually saw any of these birds at Tarnbrook and the study ended in 1994. Unfortunately during the intervening time the records of the colour-ring combinations on individual gulls seem to have been misplaced. Readers may be interested to learn that one of the adult Lesser Black-backs from this scheme was the colour-ringed bird present at the Eric Morecambe Pool in late August. It was certainly there on at least 29^th August, and then appeared on the River Lune by Lancaster Tip on 22^nd September and 19^th October.

Dr. Coulson’s letter also shed some light on the origins of three other adult Lesser Black-backed Gulls, which appeared at the River Lune – 2 on 24^th August and 1 on 16^th November. These all had a blue ring on their left leg and a combination of three colour-rings on their right leg, but curiously no metal BTO-type ring. According to Dr. Coulson these birds were ringed at South Walney sometime in the late 1980s by researchers at Oxford University. However they did not have a BTO ringing licence – hence the absence of metal rings on these birds! This ringing scheme appears to have ceased in the early 1990s and I have been unable trace anyone who was directly involved in it.

At the time of writing a ‘residual population’ of colour-ringed gulls still appears to be present in the vicinity of Lancaster Tip. Given the likely increase in coverage of gull flocks by local birders searching for ‘white-winged’ gulls in the coming months, more colour-ringed birds should be noted. Any one who does see a colour-ringed gull anywhere in the local area is encourage to pass the details on to Pete Marsh or contact either Peter Rock or David Sowter at the addresses given below.

Further reading, websites, useful addresses and acknowledgements:

Garner, M. & Quinn, D.  (1997) Identification of Yellow-legged Gulls in Britain: Part 1. British Birds 90, 25-62.

•  An excellent discussion of Yellow-legged and Caspian Gull identification.

Garner, M., Quinn, D. & Glover, B.  (1997) Identification of Yellow-legged Gulls in Britain: Part 2 British Birds  90, 369-383.

•   Over 40 colour photos of Yellow-legged Gulls, Caspian Gulls, etc. in various plumages.

Garner, M.  (1998)  Gulls: Another piece in the jigsaw  Birdwatch  74, 25-32.

• Essentially an abridged version of the above articles; includes some useful photos, though beware – three are incorrectly captioned.

Jonsson, L.  (1998)  Yellow-legged gulls and yellow-legged Herring Gulls in the Baltic  Alula 3, 74-100.

• Another essential article; includes some excellent sketches and photos – the various adult argentatus Herring Gulls with bright yellow legs are particularly striking.

www.martinreid.com/gullinx.htm

• One of a number of North American websites devoted to gull identification; contains numerous photos of Yellow-legged Gulls (some are Italian colour-ringed birds in northern Germany) and Caspian Gulls (in Europe and the Persian Gulf).

www.ping.be/cr-birding/cr-birding.htm

• The essential website for those interested in colour-ringing; contains details of 742 European schemes covering 224 species. It is not a complete list however – there is no mention of the colour-ringing of Bearded Tits at Leighton Moss, for example.

Peter Rock   59 Concorde Drive, Westbury-on-Trym, Bristol, BS10 6PX.

• The European colour-ringing co-ordinator for large gulls and thus the first point of contact for any observers wishing to trace the origins of such birds.

David Sowter   5 The Grove, Penwortham, Preston, PR1 OUU.

•  Lesser Black-backed Gulls with either a black ring + yellow code (R, T or W / number / letter / letter) or a green ring + white letter (R, T or W) on their left leg (and a BTO ring on their right leg) should be reported to Dave Sowter. The majority of colour-ringed gulls within the LDBS area are likely to be from this scheme.

Thank you to Ray Hobbs and Mike Robinson for kindly loaning me relevant issues of British Birds, Dutch Birding and Alula.

Pete Crooks            p.crooks@ucsm.ac.uk

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