15-5-2015 EBRO DELTA, TARRAGONA - EURASIAN REED WARBLER (Acrocephalus scirpaceus)

The common reed warbler (Acrocephalus scirpaceus) is an Old World warbler in the genus Acrocephalus. It breeds across Europe into the temperate western Palaearctic where it is migratory, wintering in sub-Saharan Africa. It is also a resident species over large parts of Africa.

This is a medium-sized warbler, 13 cm (5.1 in) in length with a wing-span of 17–21 cm (6.7–8.3 in). The adult has an unstreaked brown back and buff underparts. The forehead is flattened, and the bill is strong and pointed. The sexes are identical, as with most warblers, but young birds are richer buff below. The common reed warbler looks similar to the great reed warbler, but the great reed warbler is larger in size and has a stronger supercilium.

The song is a slow, chattering jit-jit-jit with typically acrocephaline whistles and mimicry added.

This small passerine bird is a species found almost exclusively in reed beds, usually with some bushes.

Like most warblers, it is insectivorous, but will occasionally take plant material such as berries.

The males return to the breeding grounds two or three weeks before the females. The species is usually monogamous. The first eggs are laid at the end of April. The nest is usually placed in vegetation over water, especially in reeds of the genus Phragmites. The deep cylindrical cup nest is sited on average 65 cm (26 in)—range is between 20 and 140 cm (7.9 and 55.1 in)—above the surface of the water and is built entirely by the female. She takes four days to build the initial cup of grass, reed stems and leaves, and another three days to complete the lining of finer material including hair. The clutch contains three to five eggs that are laid daily. The eggs are very pale green with speckles and blotches of olive green or grey. On average they measure 18.4 mm × 13.6 mm (0.72 in × 0.54 in) and weigh 1.75 g (0.06 oz). They are incubated by both parents, beginning after the penultimate egg is laid. Only the female incubates at night. The eggs hatch after 9–12 days. The nestlings are fed and cared for by both parents. They fledge after 10–12 days but continue to be fed by their parents for another 10–14 days. Up to one third of pairs raise a second brood.

The common reed warbler is one of the species that are brood parasitised by the common cuckoo.