Iduna aedon
Silhouette: Sheatherius · PhyloPic
In 3 days ~10% in a week ~20%
The thick-billed warbler (Arundinax aedon) breeds in the temperate east Palearctic, from south Siberia to west Mongolia. It is migratory, wintering in tropical South Asia and South-east Asia. It is a very rare vagrant to western Europe.
This passerine bird is a species found in dense vegetation such as reeds, bushes and thick undergrowth. Five or six eggs are laid in a nest in a low tree. This is a large warbler, at 16–17.5 cm (6.3–6.9 in) long, which is nearly as big as the great reed warbler. The adult has an unstreaked brown back and buff underparts, with few obvious distinctive plumage features. The forehead is rounded, and the bill is short and pointed. The sexes are identical, as with most warblers, but young birds are richer buff below. Like most warblers, it is insectivorous, but will take other small prey items.
The song is fast and loud, and similar to the marsh warbler, with much mimicry and typically acrocephaline whistles added. It was sometimes placed in the monotypic genus Phragmaticola (or Phragamaticola) and for a long time as Acrocephalus and in 2009 suggested as being within the Iduna clade. However, a 2014 phylogeny study based on more loci indicated that it did not fit into the Iduna clade, and therefore suggested a resurrection of the genus Phragamaticola or Arundinax; the latter, being the older available genus name, has priority.
The genus Arundinax is from Latin arundo, arundinis meaning "reed" and Ancient Greek anax which means "master". The specific aedon is from Ancient Greek aedon and means nightingale. In Greek mythology, Queen Aëdon was changed into a nightingale after killing her own son Itylus while attempting to murder one of the sons of her sister-in-law Niobe. Wikipedia →
Recording0:15
China · 2023
© wresy · iNaturalist · CC BY-NC 4.0
Recording0:14
China · 2025
© Amaël Borzée · iNaturalist · CC BY-NC 4.0
Recording0:14
Russia · 2023
© Natalia Ivanova · iNaturalist · CC BY-NC 4.0
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Manas National Park | 🇮🇳 India | |
| 2 | Gobi Gurvansaikhan National Park | 🇲🇳 Mongolia | |
| 3 | Kaeng Krachan National Park | 🇹🇭 Thailand | |
| 4 | Kaziranga National Park | 🇮🇳 India | |
| 5 | Chitwan National Park | 🇳🇵 Nepal | |
| 6 | Periyar National Park | 🇮🇳 India | |
| 7 | Doi Inthanon National Park | 🇹🇭 Thailand | |
| 8 | Khao Yai National Park | 🇹🇭 Thailand | |
| 9 | Mudumalai National Park | 🇮🇳 India | |
| 10 | Royal Manas National Park | 🇧🇹 Bhutan | |
| 11 | Sundarbans National Park | 🇮🇳 India | |
| 12 | Nagarhole National Park | 🇮🇳 India |
Rare
Under 5% of wildlife watchers report a Thick-billed Warbler sighting in Kaziranga National Park on a given day, based on 63 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 204th most-seen of the 323 birds we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
October
In that month about 20% of wildlife watchers report a Thick-billed Warbler in Kaziranga National Park on a given day, against under 5% in August–September and November–May, the lowest months. June and July have too few records to rate.
Between 7 and 10 am
Across all the parks we cover, that three-hour window holds the most Thick-billed Warbler sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
4th of 12
Of the 12 parks where we can rate Thick-billed Warbler sightings, Kaziranga National Park ranks 4th at under 5%. The best odds are in Manas National Park (India, about 10%), Gobi Gurvansaikhan National Park (Mongolia, about 10%) and Kaeng Krachan National Park (Thailand, about 10%).
GBIF citizen-science records
It is estimated from how often the Thick-billed Warbler is recorded against all the birds logged in Kaziranga National Park (63 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
