Appearance:

Olive green upperparts, yellowish chest with gradual transition to off-white belly. Very similar to Chiff-chaff, and most field characters are subtle and often hard to see. Distinguished by (usually) pale, yellow-brown legs, dark framing to ear-coverts, stronger supercilium. Long primary projection (often 3/4ths the length of tertials) with irregularly spaced tips (visible when wing folded). Wings slightly more pointed than in Chiff-chaff, and not so fan-shaped. Juveniles often with whole underparts yellow. Frequently flicks tail, but not sideways (unlike Chiff-chaff). Generally also more calm when moving among the foliage.

Sound:

By far most easily identified by it's call or song. Contact/alarm call a soft, plaintive ascending "hoo-eet". Similar to Chiff-chaff, but first part more drawn, giving it a disyllabic feel. Song: A 3-5 second, falling phrase of soft, rippling "svi-svi" sounds, starting high with some attack, and then falling in a mellow manner. The phrase lacks any conclusion, and diminishes both in strength and tempo.

Song:

Distribution:

Wikipedia: map (se also Xeno-canto below)

Ecology:

Birdlife ecology

Links:

Observation.org Latest observations

Video IBC

Image search Flickr NB! May give other species

Sound search at Xeno-canto

Featherbase

CC

Appearance:

Differs from Common Tern in shorter head, and blood-red bill. Legs shorter, but tail streamers longer (extends well past wings in sitting birds). Underparts of primaries with sharply bordered dark trailing edge (diffusely bordered in Common Tern). Both primaries and secondaries transparent to sunlight. Crest less apparent than in Common Tern and underside greyer. Cheeks white just below the black cap, often in contrast to grey lower cheeks. Juveniles lacks buff coloured back.

Sound:

Similar to Common Tern but higher pitched. Typical call a series of high pitched "tip-tip-tip", and longer, ringing, high-pitched "kriiiiii" calls. The drawn out "kree-aaahh" call falls less distinctly in pitch than Common Tern.

Calls:

Distribution:

Wikipedia: map (se also Xeno-canto below)

Ecology:

Birdlife ecology

Links:

Observation.org Latest observations

Video IBC

Image search Flickr NB! May give other species

Sound search at Xeno-canto

Featherbase

CC

CC-sound:Stein Ø. Nilsen, Licence,Link.