Iduna opaca
Silhouette: Sheatherius · PhyloPic
In 3 days ~50% in a week ~80%
The western olivaceous warbler (Iduna opaca), also known as the isabelline warbler, is a "warbler", formerly placed in the Old World warblers when these were a paraphyletic wastebin taxon. It is now considered a member of the acrocephaline warblers, Acrocephalidae, in the tree warbler genus Iduna. It was formerly regarded as part of a wider "olivaceous warbler" species, but as a result of modern taxonomic developments, this species is now usually considered distinct from the eastern olivaceous warbler, Iduna pallida.
It is a small passerine bird, found in dry open country, including cultivation, with bushes or some trees. Two or three eggs are laid in a nest in low undergrowth or a bush. Like most warblers, the western olivaceous warbler is insectivorous.
It is a medium-sized warbler, more like a very pale reed warbler than its relative the melodious warbler. The adults have a plain pale brown back and whitish underparts. Its body length is about 13–14 centimetres (5.1–5.5 in), wingspan 18–21 centimetres (7.1–8.3 in) and weight 8–13 grams (0.28–0.46 oz). The bill is strong and pointed and the legs grey. The sexes are identical, as with most warblers, but young...
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Niokolo-Koba National Park | 🇸🇳 Senegal | |
| 2 | Djoudj National Bird Sanctuary | 🇸🇳 Senegal | |
| 3 | Doñana National Park | 🇪🇸 Spain | |
| 4 | Mole National Park | 🇬🇭 Ghana |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Marrakesh | 🇲🇦 Morocco | |
| 2 | Maiduguri | 🇳🇬 Nigeria | |
| 3 | Ouagadougou | 🇧🇫 Burkina Faso | |
| 4 | Rabat | 🇲🇦 Morocco | |
| 5 | Serrekunda | 🇬🇲 Gambia | |
| 6 | Dakar | 🇸🇳 Senegal |
Possible
About 20% of wildlife watchers report a Western Olivaceous Warbler sighting in Djoudj National Bird Sanctuary on a given day, based on 29 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 116th most-seen of the 173 birds we can rate there. Over three days the chance rises to about 50%, and over a week to about 80%, if each day is a fresh chance.
March
In that month about 30% of wildlife watchers report a Western Olivaceous Warbler in Djoudj National Bird Sanctuary on a given day, against about 10% in November, the lowest month. That is one of Djoudj National Bird Sanctuary's driest months, with almost no rain against 55 mm in August. May to October have too few records to rate.
Between 8 and 11 am
Across all the parks we cover, that three-hour window holds the most Western Olivaceous 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.
Among the best
Of the 4 parks where we can rate Western Olivaceous Warbler sightings, Djoudj National Bird Sanctuary ranks 2nd at about 20%, level with the leaders once rounded. The best odds are in Niokolo-Koba National Park (Senegal, about 20%).
Same family: Acrocephalidae
The closest relatives of the Western Olivaceous Warbler that you can see in Djoudj National Bird Sanctuary (family Acrocephalidae, Reed Warblers and Allies) are Eurasian Reed-Warbler (about 30%), Sedge Warbler (about 30%) and Greater Swamp Warbler (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Western Olivaceous Warbler is recorded against all the birds logged in Djoudj National Bird Sanctuary (29 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.
