Great reed-warbler  (Acrocephalus arundinaceus)

The great reed-warbler is classified as Least Concern (LC) on the IUCN Red List (1).

The largest of the European warblers (3), the great reed-warbler (Acrocephalus arundinaceus) is most easily identified by its long, heavy bill, well-defined white eyebrow stripes, and long tail (4) (5). The great-reed warbler has warm brown upperparts, and the feathers of the wings have darker centres and pale edges (4). The underparts are greyish-white, with a warm buff wash on the flanks (4).

The male and female great reed-warbler are very similar in appearance but the juvenile is a little brighter than the adult, with an orange wash to the underparts (2).

The great reed-warbler has a harsh, guttural song, and its call is a prolonged ‘chee-chee-chaak-chaak’ (5).

The great reed-warbler breeds throughout mainland Europe and Asia, and migrates south to sub-Saharan Africa for winter (2) (6).

As this species’ name suggests, reed beds are the favoured habitat of the great reed-warbler during the breeding season. It selects tall reeds with thick stems situated close to open water in which to build its nest (2) (3). During the winter, the great reed-warbler may be found in reed beds, bush thickets (5), wet rice fields and forest clearings (7).

With a diet similar to that of other warblers, the great reed-warbler feeds on insects, spiders and small invertebrates. Outside of the breeding season, the great reed-warbler may also supplement this diet with fruit and berries (2).

During the breeding season, the male great reed-warbler performs a loud elaborate song to attract a female. Lasting from just 20 seconds up to 20 minutes without pause, this song can be heard up to 450 metres away. Having attracted a mate, the male will only sing to defend his territory against rival intruders (3). This song is much shorter and noticeably different to the song used in courtship, therefore the type of song produced is a good indicator of whether the male is paired or not (8). However, some males may move away from their territories and use the elaborate courtship song to search for multiple females (8). Although generally monogamous, this means that some males may pair with two to three females at one time (2).

The female great reed-warbler lays eggs between mid-May and early July in Western and Central Europe (2). The eggs are laid in a nest which is suspended from reed stems, over a metre above the water. The female weaves damp material around the reed stems which, when dry, will keep the nest stable (3). Incubation is carried out by the female alone and lasts for 14 to 15 days. The offspring become independent and leave the nest 12 to 14 days after fledging (2).

In August, following breeding, the great reed-warbler begins the journey south to its wintering range, where it remains until returning north in March (2).

Great reed-warbler eggs are commonly lost to predation, and its nests may also be parasitized by the common cuckoo (Cuculus canorus), which lays its eggs in the nests of other bird species (2) (9) (10).

While the great reed-warbler is not considered to be a globally threatened species, the population in Western Europe decreased by up to 50 percent between 1970 and 1990. This decline can be attributed to factors such as climate change, habitat loss and decreasing reed quality (2).

The observed population decline in the great reed-warbler is not believed to be significant enough to cause concern for this species. As it is not a particularly rapid decline and the overall population size remains so large, the great reed-warbler is not considered to be threatened with extinction, and there are no known current conservation measures in place (11).

View information on this species at the UNEP World Conservation Monitoring Centre.

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Learn more about bird conservation:

• BirdLife International:
  http://www.birdlife.org/