Radde's Warbler Phylloscopus schwarzi Scientific name definitions

Relatively little is known about the Radde's Warbler in spite of its moderately large range and relative abundance. In part, this may be due to its preference for dense vegetation and its unassuming appearance, an appearance that is rather similar to several other members of Phylloscopus. The portion of its life history that has been best elucidated is its song, a song that is not likely to enchant, as that of a Common Nightingale (Luscinia megarhynchos) might, but one that is fascinating in its complexity and produced with gusto, reaching a mean of 78.6 dB(A) at one meter. Each song can take up to 190 seconds and may contain as many as 43 phrase types, with many males producing a unique combination of phrases that have linear syntax, wherein the next phrase in a sequence can be predicted by the previous phrase.

The Radde's Warbler breeds from south-central and southeastern Siberia south to northern Mongolia, northeastern China, and North Korea, dwelling in locations with dense low growth but eschewing deep dark woodlands. Favored habitats include open taiga forest with lush undergrowth, forest openings with thick secondary growth, thickets of willow (Salix) and Daurian rhododendron (Rhododendron dauricum) along rivers and lakes, and sparsely wooded hillsides with impenetrable clusters of low woody growth, such as stunted oaks (Quercus) or rhododendron. Within these habitats, its ball-like nest is placed low in the dense cover and typically contains five grayish eggs that are densely mottled with brownish-olive spots and streaks. The Radde's Warbler arrives on its breeding grounds from late May into late June and departs from the mid-August into September.

The nonbreeding grounds, which are largely occupied from the latter half of September through April, stretch from Guangdong Province (around Hong Kong) in southeastern China west to central Myanmar and south through Thailand (excluding peninsular Thailand), Cambodia, Laos, and Vietnam. Within this region, it continues to prefer generally open areas with low dense vegetation. Its diet is presumed to consist of small insects, perhaps supplemented by seeds or small fruit. It forages in a deliberate lumbering manner through thick cover, with its body and head held horizontal, frequently flicking its tail and wings, and occasionally darting forward after prey. In the nonbreeding season, it hunts alone or in small groups, sometimes joining mixed species feeding flocks.

The Radde's Warbler was first described by Gustav Ferdinand Richard Radde in 1861 based on a specimen from southeastern Russia. It is most closely related to the Yellow-streaked Warbler (Phylloscopus armandii), from which it diverged 3–5 million years ago. The species' future does not appear to be threatened in any particular way. Its breeding density in its widespread preferred habitat appears to be 5–10 pairs/km² and it is considered common in its Southeast Asian nonbreeding grounds. However, we will not truly apprehend this species until we know more of its courtship, nesting cycle, and diet—all areas ripe for future research.