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A photo of a Thick-billed Warbler (Arundinax aedon)
Thick-billed Warbler

Thick-billed Warbler

Arundinax aedon

The Thick-billed Warbler, Arundinax aedon, is a robust passerine of considerable size, measuring 16–17.5 cm in length. It is nearly as large as the Great Reed Warbler. The adult's plumage is characterized by an unstreaked brown back and buff underparts, presenting a rather nondescript appearance. The forehead is gently rounded, and the bill is notably short and pointed. In terms of sexual dimorphism, the sexes are indistinguishable, a common trait among warblers. Juveniles, however, display a richer buff on the underparts.

Identification Tips

When attempting to identify the Thick-billed Warbler, look for its sizeable stature and the lack of streaking on its brown back. The buff underparts and the short, pointed bill are also key features. The rounded forehead may assist in distinguishing it from other warblers.


This species thrives in dense vegetation, favoring environments such as reed beds, thickets, and lush undergrowth.


The Thick-billed Warbler breeds in the temperate regions of the east Palearctic, spanning from south Siberia to west Mongolia. It is a migratory bird, seeking warmer climates in tropical South Asia and Southeast Asia during the winter months. On rare occasions, it has been recorded as a vagrant in western Europe.


The Thick-billed Warbler is known to lay a clutch of five or six eggs, choosing a nest site within a low tree.

Song & Calls

The vocalizations of the Thick-billed Warbler are a lively and resonant affair. Its song bears resemblance to that of the Marsh Warbler, incorporating a rich tapestry of mimicry and the distinctive acrocephaline whistles.


Breeding behavior includes the construction of a nest in a low tree, where the female deposits her eggs.

Diet and Feeding

An insectivorous bird by nature, the Thick-billed Warbler predominantly feeds on insects, although it will not shy away from other small prey items when available.

Conservation status

The IUCN Red List has classified the Thick-billed Warbler as Least Concern, indicating that, at present, there are no immediate threats to its population numbers warranting a higher level of concern.

Thick-billed Warbler Sounds

Recorded by: © 
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Thick-billed Warblers on Birda

A map showing the sighting location
Hemant Kirola
04 Dec 2023 - 6:32am

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