Lesser Black-backed Gulls Larus fuscus nest in all the Channel Islands, with strongholds in Alderney and Sark. Breeding numbers in the islands (c. 1,730 pairs) appear presently stable, and the whole population is believed to leave the islands in winter. A colour-ringing programme began in 2008 and the timing and pattern of arrival for 125 colour-ringed adults, believed to be local breeders, was recorded at a landfill site on Guernsey from 1 January to 8 May 2010. Birds arrived back from 15 January to 1 May. Arrivals were slow initially, with only 6% back by mid February and 22% by the end of February. Peak arrival was from 27 February to 10 March, when 34% of birds were first recorded, and by the end of March 82% of birds had returned. Males did not arrive earlier than females. Five birds left the Channel Islands again soon after arriving, although all returned within a few days or weeks. Winter 2009/10 was unusually long and cold in the Channel Islands, and most of Western Europe, and further study should ascertain whether the arrival pattern of Lesser Black-backed Gulls in spring 2010 was affected by the harsher than average winter weather.

For much of the twentieth century, populations of Lesser Black-backed Gulls Larus fuscus increased in Western Europe and the species’ breeding range and habitats expanded, probably through a combination of reduced exploitation, and new feeding opportunities at refuse landfill sites and from fisheries discards (Furness et al. 1992; Camphuysen et al. 1995; Pons & Yésou 1997; Calladine 2004). This increase continued in Britain and Ireland until 1998–2002, at least at coastal colonies (Calladine 2004), although there was a substantial decrease in UK breeding numbers between 2000 and 2003 (JNCC 2010). The causes of this recent decline are unknown, but may include the reversal of factors contributing to earlier population increases, namely decreased availability of organic refuse and reduced discards from fisheries (Calladine 2004).

Lesser Black-backed Gulls breed in all the Channel Islands (CI), with numbers having increased by 470% between 1969–70 and 1998–2002 (Calladine 2004). The CI population numbered 1,734 apparently occupied nests (AON) in 1998–2002 (Calladine 2004), with up to 1,575 of these being in the Bailiwick of Guernsey, comprising Guernsey (100–125 AON), Alderney (320–370), Sark (810–900), and Herm and its adjacent islets (140–180) (Hooper 2007). While there has been no further comprehensive census across the islands, there has clearly been further growth of the overall population, although the true extent of this has been obscured by a marked (but unquantified) reduction on Sark (pers. obs.) and a larger increase on Alderney. Counts on Burhou Island (off Alderney, now the largest CI colony) of 1,085 AON in 2005 and 1,074 in 2010 (J. Stockdale pers. comm.) suggest the CI population may now have stabilised.

British and Irish breeding Lesser Black-backed Gulls were almost exclusively migratory until the 1950s, since when numbers wintering in the British Isles increased from a few hundreds to over 60,000 by 1993 (Cramp & Simmons 1983; Hickling 1986; Burton et al. 2003), with further increases in some regions to 2004 (Banks et al. 2009); these include birds breeding in continental Europe, the Faeroes and Iceland, as well as British and Irish breeders (Rock 2002). Despite this, no large change was found in the proportion of British and Irish-ringed birds recovered dead in winter in Britain and Ireland compared to abroad, before (15%) or after 1970 (22%), nor any major change in their overseas distribution in winter (Rock 2002). The CI breeding population appears to have remained migratory and the species is scarce in winter in all the islands, with recent maximum daily counts in November/December of no more than ten birds on each of Jersey and Guernsey (Dryden et al. 2007–2009; pers. obs.), which are not thought to be local breeders.

Although over 3,500 Lesser Black-backed Gulls have been metal-ringed since the inception of the Channel Islands Bird Ringing Scheme in 1946, only once a colour- ringing scheme began in the Bailiwick of Guernsey in 2008 have individuals been identifiable in the field. This paper details the return dates in 2010 for 125 adult Lesser Black-backed Gulls colour-ringed in the CI in spring and summer 2008 and 2009.

I am grateful to the States of Guernsey Public Services Department, States Works, and the management and staff at Mont Cuet landfill, who gave me free access to ring and record gulls, and co-operated superbly with a cannon-netting operation in June 2009 run by Paul Roper and colleagues from North Thames Gull Group. I am very grateful to La Société Guernesiaise, the Guernsey branch of the Royal Society for the Protection of Birds, Creasey’s Ltd (the local Marks & Spencer franchise) and the Channel Islands Co-operative Society Ltd for financial support with gull studies in Guernsey. Finally, many thanks to all who reported Guernsey colour-ringed gulls both on the island and abroad.

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