Great Reed Warbler

The thrush-sized warbler is one of the largest species in both its current the family Acrocephalidae, and its former family, the "Sylviidae". It measures 16–21 cm (6.3–8.3 in) in length, 25 to 30 cm (9.8 to 11.8 in) in wingspan and weighs 22 to 38 g (0.78 to 1.34 oz). The adult has unstreaked brown upperparts and dull buffish-white chin and underparts. The forehead is flattened, and the bill is strong and pointed. It looks very much like a giant common reed warbler (Acrocephalus scirpaceus), but with a stronger supercilium. The sexes are identical, as with most old world warblers, but young birds are richer buff below. The warbler's song is very loud and far-carrying. The song's main phrase is a chattering and croaking carr-carr-cree-cree-cree-jet-jet, to which the whistles and vocal mimicry typical of marsh warblers are added.

The great reed warbler breeds in Europe and the west Palearctic. It does not breed in Great Britain, where only the closely related, smaller common reed warbler Acrocephalus scirpaceus occurs, but is an irregular visitor. Its population has in recent decades increased around the eastern Baltic Sea, while it has become rarer at the western end of its range. It is a migratory bird, wintering in tropical Africa. It migrates north at a rather late date, and some birds remain in their winter quarters until the end of April. The mtDNA haplotype data indicate that during the last glacial period there were two allopatric populations of great reed warbler. The great reed warblers in southwestern and southeastern Europe were at that time apparently separated by the Vistulian-Würm ice sheets and the surrounding barren lands. Though the data are insufficient to infer a date for this separation robustly, it suggests the populations became separated around 80,000 years ago, coincident with the first major advance of the ice sheets. …

The great reed warbler has a primarily carnivorous diet. Observation of prey collection specifically during breeding season has shown the retrieval of insect larvae, moths, dragonflies, damselflies, beetles, spiders, small fish, and frogs. It has also been reported to eat fruit during non-breeding seasons. Nestlings typically feed on diptera and arachnids, though this may not be their preferred food.