Sedge Warbler photographed at Claire Mare [CLA] on 28/4/2018 Photo: © Andy Marquis (visit site)

The Sedge Warbler breeding range is extensive, stretching from the high Arctic south to the mid-latitudes of the Western Palaearctic, but only marginally on the Mediterranean zone. It winters in Africa, especially south of the Sahara. Numbers in Britain began to fall in 1969 and by 1974 had fallen dramatically due to drought in the Sahelian region in western Africa. Following a partial recovery in the late 1970s, numbers fell once again to an all time low in 1985 but have recovered to former levels since then.

Although Smith had no proof, he thought that Sedge Warblers bred in Guernsey. In 1879, he wrote 'The Sedge Warbler is by no means so common as the Reed-warbler, though like it, it is a summer visitant and is quite as local.' Smith did not see any birds in Phragmites reed dominated areas but was sure that a pair of birds were breeding in an areas with 'thick willow hedges, thick grass and rushes growing by the side of the bank with a small stream in each ditch.' Since Smith's time, Sedge Warblers have bred sporadically and are a common spring and autumn migrant to Guernsey and a not-common passage migrant to Sark and fairly common in Alderney.

The mean arrival date for the first spring migrants between 1969 and 1999 was 18 April, two days before the Reed Warblers, although the first Sedge Warblers often occur at the same time as the first Reed Warblers. Sedge Warblers pass through the islands until the end of the second week in May. Most spring records come from the islands' reedbeds but during spring falls there are often early-morning records of birds singing in coastal scrub at Pleinmont or other west coast headlands. Inland records, away from the larger marshes and birds are irregularly recorded from other marshy areas such as the Fauxquets Valley and the Mare de Carteret as well as in patches of scrub on farmland.

Spring passage can be spectacular although catches of over 100 birds by ringers are very rare. However, during the spring of 1975 Paul Lee recorded up to 200 birds a day passing through the Casquets and Mike Hill recorded 43 there on 1 April 1989, showing that large numbers do pass through the area.

Sedge Warblers now only breed occasionally in Guernsey, usually in one of the islands reedbeds. Writing in the 1960 Transactions, R.W. Arnold wrote that several pairs of Sedge Warbler bred at the Track Marais and that this was the only site where this species and Yellow Wagtail bred regularly. Proving breeding of Sedge Warblers is extremely difficult and late spring and early autumn migrants can confuse. However, June records probably give the strongest indication that a bird is attempting to breed. Since 1969, there have been June records of Sedge Warblers at the following sites: the Track Marais in 1969, at this site, the Grandes Mare and La Girouette in 1970. No records were received in 1971 but a singing male was heard at the Track Marais in June 1972. The next summering record did not occur until 1977 when birds were recorded at the Grandes Mare and the Track Marais and the following year, 1978, when a bird was at 'L'Eree marsh' [La Claire Mare presumably]. In June 1979, birds were found at the Vaux de Monel and Silbe NR, and in June 1981 records were received from the Grands Marais, Vale Pond and the Marais Nord. No further records were received until a pair were proved to breed at La Rochelle in 1989. In the 1990s there have only been five mid-summer records at the Claire Mare (199X, originally ringed at Slapton Ley in the UK), La Mare de Carteret (1996) and the Marais Nord, Silbe and Grandes Mare in 1997. Most July records probably refer to passage migrants but the record of a singing bird at Fort Doyle on 16 July 1993 is intriguing.

In autumn passage begins towards the end of July, involving mostly juveniles as adults migrate in fewer long-distance flights. Passage continues throughout August and has ended by the end of the second week in September. Ringers records indicate that passage is generally slow and very dependent on weather conditions. During anti-cyclonic weather very few birds are caught but an easterly wind coupled with misty or otherwise poor weather can produce some very large falls during August.

Ringing recoveries show that birds from Britain and Ireland regularly pass through the islands although there is a strong westerly bias in the UK & Irish records. Most UK and Ireland records are of birds caught either on spring or autumn passage. Only one bird of know breeding origin was caught and that was a pullus ringed in Cumbria on 19 June 1980.