Common Reed Warbler

The common reed warbler (Acrocephalus scirpaceus) is a small passerine bird that breeds throughout much of Europe and western Asia, and wintering in sub-Saharan Africa. It measures about 12.5 to 14 cm (5 to 5.5 inches) in length, with a wingspan ranging from 17 to 21 cm (6.7 to 8.3 inches). It weighs between 10 to 15 grams (0.35-0.53 oz). This species is characterized by its relatively plain, brown upperparts and paler underparts. Its rounded wings and pointed beak are well-suited for its insectivorous diet. The common reed warbler is often confused with the marsh warbler (Acrocephalus palustris). However, it can be distinguished by its less pronounced pale supercilium and a plumage with a more brownish tone, compared to the more greenish tone of the marsh warbler. The songs are also different, with the marsh warbler having a more varied song, imbued with a lot more mimicry of other bird species.

The common reed warbler primarily inhabits reed beds and other wetland areas with dense vegetation. These environments provide ample cover and an abundant food supply. It can also be found in other marshy areas, along riverbanks, and sometimes in gardens and parks near water bodies. Its diet consists mainly of insects, including beetles, flies, caterpillars, and aphids. The warbler is adept at gleaning prey from foliage and reeds, often employing a methodical search and probing behavior. Occasionally, it will also consume spiders and small mollusks.

The common reed warbler is a migratory species, traveling vast distances between its breeding and wintering grounds. It typically migrates from its breeding sites in Europe and western Asia to winter in sub-Saharan Africa. The migration journey covers thousands of kilometers and occurs twice a year, with birds departing in late summer to early autumn and returning in late spring.

The timing of migration can vary slightly depending on geographical location and environmental conditions, but it generally peaks in September and May. During migration, the common reed warbler may be observed in various habitats, including gardens, farmland, and coastal areas.

The subspecies African reed warbler (A. s. baeticatus) of Southern and East Africa is sedentary year-round, and is by some treated as a separate species.

Breeding for the common reed warbler occurs from May to August, depending on latitude. This species builds its nest in dense reeds, often close to or over water. The nest is a deep cup made from grass, leaves, and reed stems, lined with finer materials for added insulation. A typical clutch consists of 3 to 5 eggs, which are incubated by the female for about 11 to 14 days. Both parents participate in feeding the chicks. The young fledge approximately 10 to 12 days after hatching, though they remain dependent on the parents for a short period thereafter.

The common reed warbler is known for being a common host to the parasitic common cuckoo (Cuculus canorus), which lays its eggs in the warbler’s nest, leaving the warbler to raise the cuckoo chick. 

The common reed warbler is listed as least concern on the IUCN Red List. Its population is stable, and the species benefits from its wide range and adaptability to various wetland habitats. However, local populations can be affected by habitat loss due to drainage of wetlands, pollution, and climate change impacting migration patterns.