The typical lifespan is 2 years. The song is varied, rushed and chattering, with sweeter phrases and some mimicry, typical of the "Acrocephalus" warblers. It is composed of phrases in random order, so that it is never the same. Male sedge warblers which have the widest repertoire mate with the largest number of females. The sedge warbler has a large range and an estimated Global Extent of Occurrence of 10 million square kilometres, with a large global population including between 8.8 million and 15 million birds in Europe. Data analysis by the British Trust for Ornithology has shown that fluctuations in the sedge warbler population stem from the adult survival rate, due to changes in rainfall on the birds' wintering grounds. Global changes in population have not been measured, but the sedge warbler's status is designated 'of least concern' by BirdLife International. It breeds across Europe and western and central Asia and is migratory. After feeding up post-breeding, they migrate quickly across southern Europe and the Sahara from August to September. Studies in Nigeria and Uganda suggest that sedge warblers return to spend winter at the same sites, year after year. All sedge warblers spend winter in sub-Saharan Africa, from Senegal in the west to Ethiopia in the east, and as far south as the eastern Cape Province of South Africa and northern Namibia. The route taken on the southward migration, and eventual wintering grounds, correspond to the birds' breeding grounds. Birds ringed in the United Kingdom and Netherlands are later found from south-west Iberia to Italy; birds from Sweden are recovered in central Europe and Italy; while Finnish birds are found in north-east Italy and Malta east to the Aegean region. Sedge warblers from the former Soviet Union take routes via the eastern Mediterranean Sea and Middle East. Loss of wetland areas for feeding on migration, and the expansion of the Sahara desert, pose threats to the sedge warbler's breeding population. Birds begin leaving Africa in late February, fatten up at wetlands before and probably after crossing the Sahara, and arrive in Europe from March onwards. Unlike other members of the Acrocephalus genus, the sedge warbler's range stretches from the Arctic to mid-latitudes. It is adapted to cool, cloudy and moist conditions. Though it is often found in wetlands, it can breed 500 metres or more away from water. During the breeding season, this is a species found in reedbeds, often with scrub, ditches and habitats away from water including hedgerows, patches of stinging nettles, and arable crops.