Of rings and records: Med Gulls again

A large number of Mediterranean Gulls are still present at the gull roost on the eastern bank of the River Arun just to the south of Arundel. This updates the previous post.

Numbers rose from between one and five birds at the start of the month to 42 on 11 July, peaking the next day at 97 before falling back markedly. The influx appeared to have ended, but numbers jumped again on 17 July. By 18 July there were at least 84 birds by the river and adjacent water meadows at high tide, when birds otherwise spread out along the lower reaches of the river become concentrated at the site.

Twelve of the Mediterranean Gulls have carried plastic colour rings on their legs that could be read with a telescope. Few European gulls have received the amount of attention from ringers that Med Gulls have, but even so the occurrence of 12 ringed birds within a week is notable.

Ringed Mediterranean Gulls by the Arun on 11-18 July

Ring colour	Code	Site	Date bird ringed	Ringed as:	Later locations	Seen by Arun:
White	3086	East Flanders, BE	30/5/08	pullus	BE	12/7
White	E927	Antwerp, BE	23/6/12	pullus	FR, BE	18/7
White	3NHJ	Antwerp, BE	12/5/17	3CY	BE	11/7
White	3YJE	Antwerp, BE	14/5/17	>3CY	FR	11/7, 18/7
White	3117	Antwerp, BE	10/5/18	3CY	-	11/7, 18/7
Green	7T8	Vendee, FR	18/6/11	pullus	FR, PT	12/7
Green	RNL0	Somme, FR	24/6/14	pullus	FR, SP, PT	11/7
Green	RT79	Vendee, FR	1/7/17	pullus	SP, NL	11/7
Green	RL72	Vendee, FR	1/7/17	pullus	FR	12/7
Green	RJR9	Vendee, FR	1/7/17	pullus	FR, PT	18/7
Red	PUP0	Z Mietkowskie, PL	30/5/17	pullus	-	12/7
Red	HE43	Bugyi, Pest, HU	10/6/09	pullus	UK, PT, FR	12/7

A ring means a bird’s past movements can be tracked to some extent. Most passage birds can only be identified to their particular species, and maybe their sex or age; there is no information on their specific background. But with a ring a bird gains history. It is usually a very limited and tantalising history, but it is still an individual’s record rather than an individual record.

Of course, the extent to which a bird can be tracked depends on how many people record it after the original ringer. Often this involves the bird being caught again by other ringers, but the Arun site is good for visual records because the birds are relatively close.

Of the twelve birds, five were first ringed in Belgium, four of them in Antwerp. A further five were ringed in France, four of them in the Vendee. The other two were ringed in Hungary and Poland. Their subsequent histories range from the detailed to the thin.

The variation partly depends on how long it is since they were ringed, but not always. Take the bird with a white ring numbered 3086. This was ringed as a pullus – a bird not yet able to fly – in East Flanders, Belgium way back in May 2008. But it was not recorded again until May 2018 in Antwerp, a few months prior to its appearance by the Arun on 12 July.

Contrast that with green ring 7T8. Ringed as a pullus in Vendee, France in June 2011, it was recorded a further 19 times before arriving at the Arun. Sixteen of the records, including a record of attempted nesting, came from France between 2011 and 2013. After that it went missing until it was seen at the Algarve, Portugal in January 2015, December 2017 and January 2018.

Equally well-recorded and well-travelled is green ring RNL0. Banded as a pullus in France in June 2014, it has since been seen 25 times in western and southwestern France, northwest and southern Spain, and the Algarve, with Gijon in Spain one of its preferred wintering sites.

While some birds move solely within Western Europe -- travelling south in winter from more northerly breeding or summering grounds -- this is not the only pattern. For instance red ring PUP0 was banded as a pullus at Zalew Mietkowskie in western Poland on 30 May 2017. A mere 408 days later it had flown 1,199 kilometres west to the Arun.

However, it might settle into a north-south pattern if it is anything like red ring HE 43. This bird was ringed as a pullus on 10 June 2009 at Bugyi 30 km to the south of Budapest in Hungary. At some stage it made the long journey west since on 24 July 2012 it was present at Walton Reservoir, Walton-on-Thames, UK. After that its movements took on a more north-south orientation; it was present at the Algarve on 11 November 2013 and at Digulleville, France on 11 October 2016.

Some of the records indicate that birds travel together. Two of the Arun birds were ringed within three days of each other in May 2017 at the same site in Antwerp. Meanwhile three birds -- RL72, RJR9 and RT79 – were all ringed as pulli on 1 July 2017 at the same site in France and may also have travelled together to the Arun. Indicative of this is the fact that RL72 and RJR9 were both recorded in Finistere, France in October 2017, albeit on different days, with RJR9 subsequently being seen at the Algarve.

Admittedly, RT79 wasn’t recorded in either France or Portugal, instead being recorded in Spain in February 2018 and the Netherlands in March 2018. However, there’s no reason why the bird wasn’t also in France or Portugal and its ring not recorded, or vice versa. A ring only allows a history to be established if it is seen again; otherwise it’s the same as a burnt tome at Alexandria.

Where do the birds by the Arun most recently come from? There is no clear indication from the two records where birds were last seen a month or so ago. White ring E927 was present on 19 June in East Flanders, Belgium but RJR9 was in Finistere, France on 14 June – quite different areas.

How long the birds will stay by the Arun is hard to say. Three of the birds recorded on 11 July were absent from the loaf the next day, so may have gone. But they may have been feeding in the water meadows to the east of the river. Similarly, on 18 July two new ringed birds were present but no repeats, though most of the gulls that day were feeding out on the meadows.

While none of the 12 birds was ringed as a young bird in the UK, and only one has previously been recorded here, the species is increasingly common in southern England. Indeed, they now regularly attempt to breed locally. But there is still a frisson seeing this species with its distinctive juvenile plumage, and the adult’s white wings, glossy black head and red bill and legs. Add to that the sight of a ring, with its promise of some real history, and the Mediterranean Gull can always raise the spirits.

Gulls at the Arun roost from 9 to 18 July

Species/Date	9	10	11	12	13	14	15	16	17	18
Mediterranean Gull	1	nc	42	97	42	16	nc	4	72	84
Common Gull	3	nc	9	9	20	13	nc	1	10	10
Lesser Black-backed	4	nc	1	1	2	1	nc	1	0	0
Great Black-backed	1	nc	2	2	2	1	nc	1	0	1
Black-headed Gull	245	nc	255	112	170	90	nc	41	412	268
Herring Gull	118	nc	118	56	87	55	nc	59	241	81

Note that the state of the tide and the time of day lead to major differences in the numbers of birds.

This piece was greatly assisted by the rapid response of Belgian, French, Polish and Hungarian ringing bodies to the submission of ring details.