Yellow-streaked Warbler Phylloscopus armandii    photos Sid Francis

 A rather skulky warbler that will sing it's penetrative trilling song from the depths of thick scrub. The yellow streaks, faint yellow, elongated patches on breast and belly, can be difficult to see in the field, often being more obvious in photos. It has a subtle white throat patch - not a huge stand out feature but one you do notice if the bird starts singing for an open vantage point. Its a good identification feature from similar, but far skulkier dusky and vaguely similar buff-throated. It also has a big chunky bill with obvious yellow lower mandible and is noticeably bigger than the other two birds. Like them, it also lacks wing bars and has a full cap, which instantly makes for an easy separation from other leaf warblers. And lastly its the song and its trills that are the clincher with this bird - both in finding and identifying it.

Similar species - as already noted its 

Vocalizations - trilling song

Habitat - well grown, old growth scrub -, willow.  At high altitudes 

Song here     Sid Francis iNaturalist