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).