I checked up Lesser Fish Eagle details from Birds of South Asia, The Ripley Guide by Pamela C. Rasmussen and John C. Anderton. Quoting the following from it (Vol 2. Page 87-88)


"A rather small version of Grey-headed, with smaller, shorter bill, paler brown tertials, lower back and rump, and greater primary projection nearly reaching tip of shorter tail. Adult has slightly browner head than adult Grey-headed, and dark brown tail without base; sexes similar. Juvenile is plainer brown above than juvenile Grey-headed with much more uniform wing-coverts (no pale apangles), unbanded dark brown secondaries, and no contrast between brown rump and tail; under parts are paler (especially throat), brownish and vaguely (at best) streaked with white. Older immature similar to adult, but with browner, paler-edged head and mantle. In flight, has wider wings and shorter rounded tail than similar Grey-headed; adult has dusky tail with weak bars and a broad dark terminal band. Juvenile is paler from below than juvenile Grey-headed (lacking striped breast), with marbled, almost unbanded primaries and secondaries and less prominent terminal tail-band; from above, tail is more prominently banded than adult, with a buffy tip.

Occurs: Summer visitor, along base of Himalayas from W to E Himachal (at least); resident Uttaranchal to Arunachal and lower parts of S Assam hills (Cachar and Naga hills at least; perhaps winter only); foot-hills, exceptionally to 4250m; wandering in winter to plains. Cited for Kashmir, Maharashtra and possibly Bangladesh but no specimens traced, and no definite records Bangladesh (PMT). Rare, local and declining; in small freshwater bodies, including clear streams, in forested hills, sometimes more open water [To Indonesia]".