The Eastern Olivaceous Warbler (Hippolais pallida) is a "warbler", formerly placed in the Old World warbler

Old World warbler

The "Old World Warblers" is the name used to describe a large group of birds formerly grouped together in the bird family Sylviidae. The family held over 400 species in over 70 genera, and were the source of much taxonomic confusion. Two families were split out initially, the cisticolas into...

s when these were a paraphyletic wastebin taxon

Wastebin taxon

Wastebasket taxon is a term used in some taxonomic circles to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined by their lack of one or more distinct character states or by their not belonging to one or more other taxa...

. It is now considered a member of the acrocephaline warbelrs, Acrocephalidae

Acrocephalidae

Acrocephalidae is a family of oscine passerine birds, in the superfamily Sylvioidea....

, in the tree warbler

Tree warbler

Tree warblers are medium-sized warblers belonging to the genus Hippolais, formerly placed in the "Old World warbler" family Sylviidae but now separated in the marsh- and tree-warbler family Acrocephalidae. They are found in Europe, Africa and western Asia....

 genus Hippolais . 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 to be two species:

• Western Olivaceous Warbler
  Western Olivaceous Warbler
  The Western Olivaceous Warbler, also known as 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 Hippolais ...
  
  , Hippolais opaca, and
• Eastern Olivaceous Warbler, Hippolais pallida.

It is a small passerine

Passerine

A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...

 bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

, found in dry open country, including cultivation, with bushes or some trees. 2-3 eggs are laid in a nest in low in undergrowth or a bush. Like most warblers, Eastern Olivaceous is insectivorous.

It is a medium-sized warbler, more like a very pale Reed Warbler

Reed Warbler

The Eurasian Reed Warbler, or just Reed Warbler, Acrocephalus scirpaceus, is an Old World warbler in the genus Acrocephalus. It breeds across Europe into temperate western Asia. It is migratory, wintering in sub-Saharan Africa....

 than its relative the Melodious Warbler

Melodious Warbler

The Melodious Warbler is an Old World warbler in the tree warbler genus Hippolais. It breeds in southwest Europe and northwest Africa. It is migratory, wintering in sub-Saharan Africa....

. The adult has a plain pale brown back and whitish underparts. The bill is strong and pointed and the legs grey. The sexes are identical, as with most warblers, but young birds are more buff on the belly. It has a characteristic downward tail flick.

Eastern Olivaceous Warbler breeds in south east Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and the Middle East. It is migratory

Bird migration

Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...

, wintering in sub-Sahara

Sahara

The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...

n Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 or Arabia

Arabian Peninsula

The Arabian Peninsula is a land mass situated north-east of Africa. Also known as Arabia or the Arabian subcontinent, it is the world's largest peninsula and covers 3,237,500 km2...

. It is a rare vagrant to northern Europe.

Western Olivaceous Warbler differs from this species in being larger and having a browner tinge to the upperparts; it also has a larger bill. Eastern Olivaceous Warbler sometimes has a greenish tinge to its upperparts, and can be very difficult to separate from Sykes's Warbler, Hippolais rama. The song is a fast nasal babbling.

North Africa

Eastern Olivaceous Warbler of the subspecies reiseri is thought to be locally common as a breeding species in southeast Morocco.